# Coolant Loss Solved (Hopefully)



## obermd (Mar 3, 2012)

My ECO MT has continued to drop coolant. Fortunately I had florescent dye in the coolant tank and this dye dries a sickly orange color. I had this dried dye all over the tank vent channel. When I took my car in for no A/C, I mentioned that my tank/pressure cap was excessively venting and I had the evidence in the form of florescent dye residue all over the vent channel.

I have a new service advisor and he looked at my car's history and erroneously thought I was complaining about coolant odors so he put the vent reroute tube on my car. I had him remove the tube when I explained that I'm not having any coolant/glycol odors either in the engine bay or in the cabin and that tube is nothing more than an ill-advised band aid until the real causes of the glycol odors were found and fixed. Ill-advised because this tube doesn't fix the underlying problem, but simply attempts, and unsuccessfully at that, to mask the odor by routing it away from the HVAC intake. Fortunately the tube and tape hadn't been on long enough to leave residue on the tank, so the outside of the coolant surge tank is actually now cleaner than it has been in a long time. I printed a copy of the coolant odor summary I put together and gave it to him when I picked up my car.

What they did find was a flat spot on the O-Ring in my pressure cap, so they put a new pressure cap on my tank.


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## Blue Angel (Feb 18, 2011)

Hopefully that solves it, but if that flat spot on the o ring was caused by the tank the new ring will likely suffer the same fate. Have you inspected the tank opening yet?


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## obermd (Mar 3, 2012)

I'm going to inspect the tank opening in the morning while it's cool outside. I have, however, been loosing about a quarter inch of coolant each month since I purchased my ECO in January 2012.

I'm also going to clean the vent cover as that didn't get cleaned and actually had to be retrieved from the bay's trash pile. This will help me keep track of excessive venting. Also, since the vent was last cleaned I haven't had more than a 2,000 ft elevation change on any given trip, so I know this wasn't a result of the 2 PSI external atmospheric drop that I get when driving across I-70.


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## obermd (Mar 3, 2012)

I just inspected the tank rim. I discovered two burs on the rim right where the left and right halves of the tank cover are welded together. Took a fingernail file and filed them flat. I also cleaned the vent cover.

This new cap "clicks" into place. My old cap didn't, so there has been a change in the cap design.


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## Blue Angel (Feb 18, 2011)

obermd said:


> I just inspected the tank rim. I discovered two burs on the rim right where the left and right halves of the tank cover are welded together. Took a fingernail file and filed them flat. I also cleaned the vent cover.


Good stuff! Hopefully that vent cover will stay sparkly clean.



obermd said:


> This new cap "clicks" into place. My old cap didn't, so there has been a change in the cap design.


Interesting! I have to say this is a welcome change... too bad the cap I bought was the old design.

I wish this story weren't true, but it is so I have to tell:

While I was at the dealer trying to convince them to sell me a new expansion tank and cap for my one year old car, I demonstrated the defect on a brand new Cruze that was sitting in the showroom. I showed the Service Manager the defect on the inside of the tank opening (to which he looked completely un-interested), then he proceeded to screw the cap back onto the tank. As we all know, the cap screws onto the tank with ease... almost too easy. Well, when he had the cap screwed on fully (the tab on the cap hit the tab on the tank), he proceeded to give'r a good twist to make sure it was tight. This broke the tank tab off. He acted as if nothing happened, slammed the hood and told me to go speak to the parts manager.

Maybe that new "click" designed into the cap is to keep Service Managers from breaking cars.


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## obermd (Mar 3, 2012)

My old cap was really hard to turn on and off. The new cap came off really easily which made me a little nervous but when it clicked into place when I put it back on I twisted it slightly each way and there is a definite wiggle, but the cap won't come off by accident.


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## Blue Angel (Feb 18, 2011)

Funny, both of my caps (both the older non-click design) spin on and off very easily, as did the one on the new Cruze in the showroom.


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## obermd (Mar 3, 2012)

The best description of the click is it feels like our gas caps do. Screw on until it clicks. Then it has a small amount of wiggle room but if you twist firmly it will screw right off. I guess GM decided if the gas caps can be held on this way with pressurization why not the coolant pressure cap as well.


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## CruzeEcoBlueTopaz (Jan 5, 2012)

Thanks for the information I was planning on replacing my coolant cap as well after I suspected some evapporation from a faulty cap. I have filled the reservoir twice over the past 130k miles. So the drop in coolant was slow but steady. 

One thing I have noticed is that when my reservoir is filled to max the coolant temperature seems to be a few degrees cooler.


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## BigSkyMontana (Jan 5, 2013)

obermd said:


> I have, however, been loosing about a quarter inch of coolant each month since I purchased my ECO in January 2012.


Been monitoring my coolant tank since I had my cowl sealed and HVAC R/R'd. I have noticed that my coolant level also is dropping 1/4" monthly. No evidence of leaks or residue around tank or engine. Since summer heat is moving in I also noticed a much stronger coolant smell under hood. Thinking a mix of warmer temperatures and a hotter running engine may cause an increase in the coolant odor under the hood. Not too concerned, but thinking the coolant is evaporating out of the vent as the warmer temps moved in and the engine possibly running a little hotter after parking.


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## obermd (Mar 3, 2012)

BigSky, stop by your dealership and have them put the florescent dye in the coolant (I think it's about $10 but they may just do it for you.) Drive for a month - it will be very obvious if the cap is the leak.


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## BigSkyMontana (Jan 5, 2013)

obermd said:


> BigSky, stop by your dealership and have them put the florescent dye in the coolant (I think it's about $10 but they may just do it for you.) Drive for a month - it will be very obvious if the cap is the leak.


Sure, good thought. I'll give it a shot and see what transpires.


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## CyclonicWrath (May 14, 2013)

My car was doing this and it was a every so small leak actually coming out of the water pump nothing over heated but I'd lose about a line gap worth of coolant every 5k km and they did the due check but I do belive they had to take the water pump pulley off to see the leak with the dye and the dye is seen under a black light not a orange burning mark, coolant will leave a white residue if it is burnt or heated to evaporation... Just my 2 cents I have a 2012 Cruze RS 6MT just for your reference, since water pump has been fixed I do not see a loss in coolant


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## CyclonicWrath (May 14, 2013)

And they should do the dye for free if the cars under warranty it is covered under the 160k km power train warranty


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## obermd (Mar 3, 2012)

Correct about the warranty - I spaced it. Mine dye was free and if the dealership is constantly having to refill the coolant it would actually be cheaper for them to put the dye in and figure out where the leak is.


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## newsguy99 (May 24, 2013)

When I went in for my coolant level check, and fill up, the service manager said that DEXcool is a dye.. and would show up..


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## obermd (Mar 3, 2012)

newsguy99 said:


> When I went in for my coolant level check, and fill up, the service manager said that DEXcool is a dye.. and would show up..


It will show up, but not nearly as well as the florescent dye that GM has to put in the DEXCool. DEXCool is reddish as a liquid but tends to dry clear to white and this dye turns a sickly orange. I couldn't see any DEXCool residue on my surge tank vent but the dye was real obvious.


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## cruze01 (Mar 25, 2011)

I've had this problem now with both my Cruz's, my 2011 1.4 would loose coolant at a pretty steady rate and now my 2013 1.4 is doing the same thing. I've got 11k on her now and the tank level is down to the third mark. I hate to have the dye added, they done that to the 2011 and all it done was stain up the tank so you could no longer see the coolant level. They changed the water pump and the tank and cap twice but still it would loose coolant. I don't want to start the mess on my new one, just trying to be satisfied until I see a real fix come out.


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## obermd (Mar 3, 2012)

There are real fixes for loss of coolant. The problem is that you have to first find the leak point, which can be very hard to do for a seeping loss.


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## cruze01 (Mar 25, 2011)

obermd said:


> There are real fixes for loss of coolant. The problem is that you have to first find the leak point, which can be very hard to do for a seeping loss.


I wonder if the seep is internal somehow. I know they gave it every effort on the 2011,dyed and searched that engine top to bottom inside and out several times but nothing was ever found! I think it may somehow be getting into the combustion chamber and blowing out the exhaust. It's such a small amount it could go undetected forever.


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## obermd (Mar 3, 2012)

The 2011s did indeed have an internal coolant leak that would seep out the water pump mount bolt holes. It was nearly impossible to detect, even with the florescent dye in the system. What this dye will do is make it very obvious if the surge tank/cap combination isn't holding pressure.


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## CyclonicWrath (May 14, 2013)

If it leaks in the motor your oil would be raising every day and is not good for an engine if it leaked inside the motor they better replace the hole motor, because of a wrong bolt putting a hole into the block causing coolant to pass inside the motor, but if they do the dye check it is more then likely the water pump leaking out of the side where it is pressed fit together all cruzes that I know that have had a violent leak have been the motor or there heater core exploded but if your heater core went you would smell a profuse smell in the cab of anti freeze, it's more then likely the water pump go to a better dealer of you still can't get this problem resolved


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## H3LLON3ARTH (Dec 16, 2011)

CyclonicWrath said:


> If it leaks in the motor your oil would be raising every day and is not good for an engine if it leaked inside the motor they better replace the hole motor, because of a wrong bolt putting a hole into the block causing coolant to pass inside the motor, but if they do the dye check it is more then likely the water pump leaking out of the side where it is pressed fit together all cruzes that I know that have had a violent leak have been the motor or there heater core exploded but if your heater core went you would smell a profuse smell in the cab of anti freeze, it's more then likely the water pump go to a better dealer of you still can't get this problem resolved


The best way to tell of your coolant is leaking into the motor you oil will turn milky and usually enters through the headgasket if you suspect thia have your dealer do a block test this will usually determine if your leaking coolant.

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## obermd (Mar 3, 2012)

Just to remind folks - I'm not claiming that this solution will work for everyone. What I do know is that my surge tank/pressure cap was venting, my coolant level was set to the full cold line, but that I haven't driven my car over mountain passes that would reduce the cap's rated 20 PSI pressure holding. The only way I could see this venting was from the dye that I had added to my coolant system last year.

Also, before anyone asks, I checked Penguin LS today and it hasn't had any coolant level drop since purchased in May 2012.


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## Blue Angel (Feb 18, 2011)

I just went and checked my car, and sure enough my coolant is down just a little from the fill mark, maybe not quite 1/4". I topped it right up after replacing the surge tank so it looks like there's a tiny bit of coolant going somewhere. In this case it's a little over two months driving.

Since replacing my surge tank and cap I am getting ZERO venting... that vent deflector on the tank is as clean as a whistle.

I can get a faint coolant odor from time to time under the hood when shutting the car off. I know trying to locate a coolant leak by smell isn't a very accurate method, but sticking my nose around it seems the smell is coming from somewhere near the drivers side end of the cylinder head where the coolant outlet is. Maybe I need to take a tube and smell through it so I can better locate the smell.

This is going to bug me now... ignorance is bliss!


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## CyclonicWrath (May 14, 2013)

Haha smelling won't help get the fluorescent dye and let it run its course, sounds like the water pump, no if ands or butts


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## alyupe11 (Jun 9, 2013)

Wow good information


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## BigSkyMontana (Jan 5, 2013)

After reading this and another thread related to the coolant loss issue in the surge tank, it appears that others are experiencing the same problem and this is an ongoing issue. So where is the coolant going? Some speculate seepage possibly around the thermostat housing or water pump bolt area. Others believe coolant may be evaporating based on turbo performance. Others?--possibly venting/evaporating from the surge tank? Even a pin hole somewhere could drive you crazy. So, to me, it appears that it remains a mystery unless a leak or seepage is confirmed. It appears that I am losing 1/4" monthly, so, I have decided to monitor and document loss and refills until something changes or I can confirm a leak. I am going to pass on the dye at this time as I have "been there, done that" with no leaks detected (not saying there may be seepage somewhere thats hard to detect). I have replaced both my surge tank and pressure cap when I configured my tank back to its original state to rid of the (tape/tube bandaid job), so I am going to gamble that I don't have a tank or cap issue at this time. The coolant smell under my hood didn't become more evident until the warmer weather moved in this month. I just noticed coolant loss starting last month. Within a two month period it has been consistent in 1/4" drop both highway and city driving mixed. I am getting ready to turn 10,000 miles. Hopefully, something or someone will be able to provide more concrete info regarding this issue.


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## CyclonicWrath (May 14, 2013)

BigSkyMontana said:


> After reading this and another thread related to the coolant loss issue in the surge tank, it appears that others are experiencing the same problem and this is an ongoing issue. So where is the coolant going? Some speculate seepage possibly around the thermostat housing or water pump bolt area. Others believe coolant may be evaporating based on turbo performance. Others?--possibly venting/evaporating from the surge tank? Even a pin hole somewhere could drive you crazy. So, to me, it appears that it remains a mystery unless a leak or seepage is confirmed. It appears that I am losing 1/4" monthly, so, I have decided to monitor and document loss and refills until something changes or I can confirm a leak. I am going to pass on the dye at this time as I have "been there, done that" with no leaks detected (not saying there may be seepage somewhere thats hard to detect). I have replaced both my surge tank and pressure cap when I configured my tank back to its original state to rid of the (tape/tube bandaid job), so I am going to gamble that I don't have a tank or cap issue at this time. The coolant smell under my hood didn't become more evident until the warmer weather moved in this month. I just noticed coolant loss starting last month. Within a two month period it has been consistent in 1/4" drop both highway and city driving mixed. I am getting ready to turn 10,000 miles. Hopefully, something or someone will be able to provide more concrete info regarding this issue.


Lol you can't find a leak without the dye just because the missed it before don't mean they will again, but if you like to just play the guessing game and never get it fixed well by all means its your car.... But new cars no matter what don't drop coolant, or evaporate lmao


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## Blue Angel (Feb 18, 2011)

CyclonicWrath said:


> Lol you can't find a leak without the dye just because the missed it before don't mean they will again, but if you like to just play the guessing game and never get it fixed well by all means its your car.... But new cars no matter what don't drop coolant, or evaporate lmao


I used to think the same thing since I've owned cars that NEVER lost a drop of coolant. USED to think that, that is, until we got a new '11 BMW 3 Series. The coolant level light came on after about a year so we took it in and they topped it off saying it's normal. I thought WTF, that a load of BS... so I looked on BMW forums and found TONS of people with the same issue; slow loss of coolant and no fix, just bring it by the dealer for a free top-up. Our dealer said sometimes they get 4-5 cars a day coming in for a top up.

My BS meter is still sitting at a medium level because I think a car should (and can be) be designed to not lose any coolant, ever. Is it possible the Cruze has a similar problem/issue/character flaw/charm? Her BMW never smells like coolant, yet it slowly vanishes. The plot thickens.


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## CyclonicWrath (May 14, 2013)

Haha mine don't lose coolant anymore and that's just BMW fixing there problem better to just fill it up then fix it


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## tdc (Jan 24, 2014)

Blue Angel said:


> I used to think the same thing since I've owned cars that NEVER lost a drop of coolant. USED to think that, that is, until we got a new '11 BMW 3 Series. The coolant level light came on after about a year so we took it in and they topped it off saying it's normal. I thought WTF, that a load of BS... so I looked on BMW forums and found TONS of people with the same issue; slow loss of coolant and no fix, just bring it by the dealer for a free top-up. Our dealer said sometimes they get 4-5 cars a day coming in for a top up.
> 
> My BS meter is still sitting at a medium level because I think a car should (and can be) be designed to not lose any coolant, ever. Is it possible the Cruze has a similar problem/issue/character flaw/charm? Her BMW never smells like coolant, yet it slowly vanishes. The plot thickens.


Your BS meter's working well (I think). I replaced my 95 Corolla (1.6L/Auto 3 speed) with a used 2012 Cruze LS/Auto/10,600 miles @ time of purchase, and currently at 14,800 miles. That Corolla did not lose ANY coolant until it reached ~190,000 miles. Then, I had a very slow leak, visible at the thermostat housing, at the fitting where the hose is connected with a clamp. (Just saying).


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## Blue Angel (Feb 18, 2011)

tdc, I replied in the other thread as well.

An FYI for those following this thread, my coolant level has stayed steady for months since fixing my tank to cap seal. I actually have it over filled and it's still sealed up tight, no venting so far. This involved replacing my faulty surge tank (defect in the throat sealing surface) as well as installing a thicker o-ring. Anyone interested in the o-ring can send me a PM.


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## cruze01 (Mar 25, 2011)

I'm 8 months and around 10k miles out since they installed the newest model of the water pump on mine. So far I haven't lost a drop of anti-freeze. I do still "think" I smell it now and then but the tank says I'm crazy...


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## obermd (Mar 3, 2012)

While checking my spark plugs today I noticed that my surge tank vent was solid with coolant vapor residue (remember I have the dye in my coolant) and that my coolant level had dropped nearly an inch in the last week and a half. I took the cap off and the inside of the cap was completely soaked in coolant. Basically the o ring had failed. Since I needed to take a test drive after the spark plug work I went to Ed Bozarth Park Meadows and purchased a replacement cap. I also just ordered the o ring Blue Angle is using. When it comes in I'll replace the failed o-ring on my original cap and put that on.


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## Chevy Customer Care (Oct 29, 2011)

obermd said:


> While checking my spark plugs today I noticed that my surge tank vent was solid with coolant vapor residue (remember I have the dye in my coolant) and that my coolant level had dropped nearly an inch in the last week and a half. I took the cap off and the inside of the cap was completely soaked in coolant. Basically the o ring had failed. Since I needed to take a test drive after the spark plug work I went to Ed Bozarth Park Meadows and purchased a replacement cap. I also just ordered the o ring Blue Angle is using. When it comes in I'll replace the failed o-ring on my original cap and put that on.


Hey Mike,

Be sure to let us know of any updates after you replace your cap. Hopefully that will solve the coolant concern! 

Patsy G
Chevrolet Customer Care


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## obermd (Mar 3, 2012)

Patsy, I'll check the level in a week or so.


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## obermd (Mar 3, 2012)

New o-ring arrived today. Since Saturday the new cap doesn't appear to have allowed very much coolant through, but some has been vented - the vent channel was coated with coolant. I put the new o-ring on my original pressure cap and put that cap on my tank. There was a huge difference in the resistance as I screwed the cap down. It feels like the tank opening is slightly X shaped as the cap got progressively harder to screw down and then on the very last half turn of the cap it got slightly easier. Now I watch and wait.


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## obermd (Mar 3, 2012)

Checked my coolant level today. The level hasn't changed since I put the new, slightly larger o-ring on the. In addition, for the first time since I started watching my coolant levels some 45,000 miles ago I have no coolant residue in the surge tank's vent channel. The level is sitting right at the top of the arrow.


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## BowtieGuy (Jan 4, 2013)

Is this still being tested as a possible fix before being fully endorsed?


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## Blue Angel (Feb 18, 2011)

BowtieGuy said:


> Is this still being tested as a possible fix before being fully endorsed?


As far as I know, Mike and I are the only two attempting this so far. If you wanted to try it out you're welcome to, just know that it's an experiment at this point and although there's little risk of anything going wrong, it is unproven.

I must add a few notes as well. There seems to be a HUGE variation in the amount of o-ring contact from car to car. Most of the cars I've looked at have very loose fitting caps; very little resistance when screwing the cap on, meaning little o-ring compression in the tank opening. Some cars, however, have much tighter caps indicating a narrower tank opening and good o-ring compression.

I have to assume that this larger o-ring modification is more likely to only help your car if you have a loose fitting cap, and may not even FIT at all if your cap is tight. Both my original tank and the replacement were loose fitting.

I stopped by a dealer last night and looked at two used Cruzes that we're sitting with the hoods open. BOTH those cars had right tanks, yet BOTH were low on coolant. When I removed the caps it was obvious there was venting taking place as both had lots of moisture and coolant residue inside the cap. Neither car had any defects in the tank opening (like my original tank did), so I can only guess that the caps were not functioning properly and leaking below the designed 20 psi threshold.

My recommendation is this:

Check your cap to tank tightness and make sure the throat is smooth and defect free.

If there's a rough section in the tank opening you need a new tank.

If it's smooth and defect free but loose fitting, try the larger o-ring. If that doesn't work the cap is most likely leaking and you need a new cap.

If it's defect free and tight fitting, the larger o-ring may not help or even fit. Try a new tank cap. If that doesn't work ask the dealer to test your cap(s). My dealer claimed they couldn't test the cap, which I think was a load, so your results may vary.

Yes this seems like a bunch of trial and error, but these o-rings are pretty cheap and the caps aren't much either.

I've been through quite a bit of trial and error at this point and I do now have a tank that doesn't vent coolant. I have a loose fitting defect free tank with the larger o-ring and a functional cap, and all is well now. Knock on wood!


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## BowtieGuy (Jan 4, 2013)

Good notes. I will check my tank this weekend when I (finally) check my plug gaps now that I have a quality plug gapper and feeler gauge set and probably send a PM about the O-ring you guys are using if I have a loose fitting cap.


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## obermd (Mar 3, 2012)

Both my original cap and the replacement I purchased are loose fitting. The original cap flat out no longer holds pressure and I can see the coolant all over the inside of the cap between the two o-rings in the cap. With that cap I lost a third of an inch of coolant in less than a month. The replacement cap allowed coolant through but not nearly as much. I put the new o-ring on the replacement cap and haven't had coolant drop since. My original cap was tested to hold 20 PSI of pressure, so I know that some dealerships can test this.


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## Blue Angel (Feb 18, 2011)

Great info mike, hopefully that new o-ring fixes'er up good.



obermd said:


> Both my original cap and the replacement I purchased are loose fitting.


My impression is that the tank is the cause of the loose fit, not the caps. That's probably what you meant, it just sounded backwards.


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## obermd (Mar 3, 2012)

Blue Angel said:


> My impression is that the tank is the cause of the loose fit, not the caps. That's probably what you meant, it just sounded backwards.


Doesn't matter to me which was causing the fit to be loose - adding the slightly thicker o-ring tightened the fit sufficiently to create a good seal.


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## BowtieGuy (Jan 4, 2013)

Are the there any concerns about possibly overpressurizing the tank? As in if the new o-ring might allow too much pressure to build in certain situations?


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## Blue Angel (Feb 18, 2011)

BowtieGuy said:


> Are the there any concerns about possibly overpressurizing the tank? As in if the new o-ring might allow too much pressure to build in certain situations?


No worries there. It is the relief valve in the cap that releases pressure, which has nothing to do with the o-ring.

The o-ring should be 100% sealed at all times if the system is working properly.


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## obermd (Mar 3, 2012)

Before putting either a new cap or a modified with larger o-ring cap on the tank, take a paper towel and wipe down the inside of the tank opening. This will remove any non-stain residue from where the o-ring makes contact.


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## carbon02 (Feb 25, 2011)

Sent a PM to Blue Angel. I've read this thread, as well as the Iconic 80 page coolant smell thread that obermd & Blue Angel posted to about a year ago. 

Can either of you PM me with a source for the gasket on the cap that you're using?

Thanks-

Carbon02


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## cruze2011white (Feb 2, 2011)

Does using the new o-ring on the cap also stop the coolant smell that some people complain they get a lot of?


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## obermd (Mar 3, 2012)

cruze2011white said:


> Does using the new o-ring on the cap also stop the coolant smell that some people complain they get a lot of?


If it's coming out via a bad seal to the tank vent it will stop any odors from this source.


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## cruze2011white (Feb 2, 2011)

Ok where do you get a new o-ring?


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## Blue Angel (Feb 18, 2011)

cruze2011white said:


> Ok where do you get a new o-ring?


Send me a PM and I'll give you the details.


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## RedChevy (May 22, 2011)

Took my car in today for the smell (now only outside the car since they did the reseal of the cowl/tube tape job) and coolant loss. The coolant loss was very bad this summer (going from 'full' to just above the lower hose in less than 2K miles).

I asked for dye to be added but didn't get it.

I was told that I need a new surge tank because one of the hoses isn't sealing properly (isn't that what clamps are for?).

They told me that it's not covered under warranty because I'm passed 3 years (I only have 34900 miles) even though I documented it before my warranty was up.

Since they didn't have the tank in stock I took the car back without making an issue but I do feel this should be done under warranty...

In the mean time I have ordered the oversized o-ring and will try that.

I'm very disappointed that GM continues to shirk the real issue....a poorly designed system with inconsistency of parts quality. (my cap is very loose and so is the replacement I bought...I don't remember it being so loose originally).

PS: They asked me if I was interested in trading in for a 2014 since my car fit their (low mileage) criteria. I will be in the market for a small SUV later in the year and it won't be an Equinox if they don't fix this problem SOON and at their cost.


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## ChuzCruze (Feb 9, 2012)

Yup, I had the same experience after escalating my issues to GM directly. Shortly after, the dealer I had bought the car through, they called me and said they wanted to help me get out of my vehicle and into a new GM. In actuality they just wanted me to trade it in on a new GM. No thanks!! Never going to make the mistake of buying another GM vehicle LOL. Live and learn.


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## carbon02 (Feb 25, 2011)

I also ordered the o-ring and installed it. 

I can screw the cap down completely, except for the last complete turn. I even lubed the o-ring and the neck of the bottle with coolant. 

I assume this is tight enough, and there is no need to "bottom out" the cap, because it's not sealing under the cap, rather at the sides of the bottle throat?

It should still vent properly as well? 

I haven't driven the car yet to pressurize, but the old o-ring on the cap was vary flat over time, and I can see it may have been a problem leaking. 

The actual pressure relief of the cap is based on spring tension isn't it? If that is the case, I would believe a failing cap that is not based on o-ring sealing would be really rare. Unless the cap was so old the inside spring was corroded.


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## Blue Angel (Feb 18, 2011)

carbon, I replied to your PM.

For those following along, the only issue I could see with not seating the cap fully is the strength of the threads not being sufficient to hold against the pressure of the cooling system.

If the thicker o-ring is too hard to install (likely in a tight fitting tank/cap scenario), a regular size o-ring made from a better material may be the answer. I will do a write up to cover both options and post it in the Service Issues forum in a couple days.


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## MyShibbyEco (Jan 21, 2012)

I'm not sure how common Ace Hardware is, but my local one carries virtually every diameter and thickness o-ring imaginable, and usually for less than $1. The material doesn't need to be anything special to withstand the heat and chemical of coolant. It's not like gasoline where it can swell the rubber, and if it did that might not be such a bad thing for sealing.


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## Clausses (Sep 8, 2014)

RedChevy said:


> Took my car in today for the smell (now only outside the car since they did the reseal of the cowl/tube tape job) and coolant loss. The coolant loss was very bad this summer (going from 'full' to just above the lower hose in less than 2K miles).
> 
> I asked for dye to be added but didn't get it.
> 
> ...


Can you find a link or part number for the oring you ordered? Thanks!


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## carbon02 (Feb 25, 2011)

I've been in contact with Blue Angel, and I know he's working on some suggestions for alternative sizes and materials for this o-ring. 

I installed the cap as tight as I could. Then allowed car to sit for 24 hours. Then removed and reinstalled the cap all the way. 

It appeared that it worked well, but differences in the molding of the tank may make this a difficult modification to suggest with a one size fits all. 

Developing a "kit of O-ring sizes" may be the best scenario. Shipping is expensive for 1-2 O-rings, so ordering several different sizes may be the best solution. 

I'm also interested in what Blue Angel may find out with his latest experiments. I need to drive more miles than 1 day with my solution to see if I can find a somewhat long solution. 

From what I've read BUNA is good for temperatures up to 250F, and personally I believe that a coolant system under pressure at 220F is too close to the maximum allowable design temperature. Causing the bottom o-ring of the cap to form a serious flat spot. 

After time this flat spot causes the cap to vent around the bottom o-ring. This is simply my best guess, and as always I'm not responsible for your safety, or damage to your car if you try this.


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## obermd (Mar 3, 2012)

The Buma o-ring also doesn't hold up well in severe cold. It gets too stiff and vapor gets around it before the car has a chance to really warm up the o-ring.


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## carbon02 (Feb 25, 2011)

Update-

Being careful I was able to install the 4.5 mm x 23 Buna O-ring. What a difference in warm up time and operation. There's no under hood smells of coolant on the passenger side. 

It also seems like the converter heat shield on the exhaust is getting hotter, as there's more expansion noise from that area on shutdown. Sheet metal pinging as the heat shield cools down. 

This proved to me that I was continually venting coolant. The system was rarely completely sealed. There's lot's of factors that contribute to MPG, but it appears that the increased speed of warm up has brought my mileage up to where it was during the first year of owning the Cruze. I have compulsive fuel tracking disorder. I've tracked mileage on every gallon of fuel pumped over the last 20 years! 

Thank you to Blue Angel and others who initially tried this, it's worked for me!


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## Blue Angel (Feb 18, 2011)

carbon02 said:


> Thank you to Blue Angel and others who initially tried this, it's worked for me!


Thanks for the feedback! Hopefully others with this issue can give it a try as well.


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