# Very slow coolant leak on 2014 Diesel



## Tomko (Jun 1, 2013)

Drop some dye in and check it a few days later. 

My guess is head gasket.


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## starspangled6.0 (Apr 16, 2016)

I'll have to check that out. I'm not seeing any milkish crap in the oil, though.


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## Rivergoer (Mar 30, 2017)

My 2014 CTD lost a water pump at 64,000 miles which I'm told is pretty rare. Apparently very common issue with the gas models but not diesels. 

Unlike your issue, my coolant leak went from zero to fail without warning. Took a short 5 mile jaunt into town for breakfast and came out to discover a large puddle of orange coolant.

Chevy replaced the water pump, timing belt and tensioner under warranty, no charge. Details posted under Gen 1 Diesel Water Pump Failure.

Good luck, hoping yours is an easy problem to identify and fix.


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## starspangled6.0 (Apr 16, 2016)

Thank you. I had the head gaskets go on my 97 Sierra, and it did the same thing as yours: fine one minute, and then oceans of coolant everywhere the next. 

I bought some dye on Amazon and it will be here tomorrow. Hopefully it's either a small fix, or if it is the pump or head gaskets, it's something I can identify and then show the dealer so they can replace it under warranty. Would much rather do it myself though :/


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## boraz (Aug 29, 2013)

put a new o ring on the cap

its been documented on here before


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## starspangled6.0 (Apr 16, 2016)

boraz said:


> put a new o ring on the cap
> 
> its been documented on here before



Is that just a new o-ring, or a new cap and reservoir, too?


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## Robby (Mar 1, 2013)

'O' ring if you can locate one.....otherwise just replace the cap. Cap replacement is always the first step if no leakage (trails) are evident.

Rob


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## theonlypheonix (Oct 8, 2015)

starspangled6.0 said:


> I've been tracking a coolant leak for the past few months... I feel like it was happening last year too, but I always chalked it up to the typical/occasional need to add a splash of coolant to most vehicles. It loses about 1 hash mark of coolant every 2 weeks, or at least it's doing that now that temps are in the low 90's where I'm stationed. Those are the average temps in the shade, but it's in the low 100's in the sun on a cool day.
> 
> Any thoughts on what this is? I can't find any leakage from a visual check in the engine bay, and have never once seen a puddle. My first thought was water pump, but I'm also wondering if the cap is venting fluid from all the excess heat.


Could be a small leak that evaporates before it hits the ground, therefore no puddles. If possible try running your finger under the connections to see if there is small seepage. Can't say that I've seen any issues of head gasket problems with these engines yet, especially the un-modified or un- tuned ones anyways.

Might not hurt to put a scan gauge on to monitor your coolant temperature to see if you are running unusually high which might cause the reservoir to burp a little out on the days when temperatures are high esp if there is a thermostat problem.


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## starspangled6.0 (Apr 16, 2016)

So I dumped in 1oz of ACDelco dye in the coolant 2 days ago, and checked it this morning with a UV flashlight. I couldn't see any dye reflections anywhere on the motor (oddly enough, not even in the coolant tank). The oil checks out good too. The coolant cap always has lots of moisture on the underside of it, even when it hasn't been driven for a while, so I'm guessing it's the o-ring that's bad. Will replace that next.


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## Tomko (Jun 1, 2013)

starspangled6.0 said:


> So I dumped in 1oz of ACDelco dye in the coolant 2 days ago, and checked it this morning with a UV flashlight. I couldn't see any dye reflections anywhere on the motor (oddly enough, not even in the coolant tank). The oil checks out good too. The coolant cap always has lots of moisture on the underside of it, even when it hasn't been driven for a while, so I'm guessing it's the o-ring that's bad. Will replace that next.


Check for dye in your oil.


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## theonlypheonix (Oct 8, 2015)

Tomko said:


> Check for dye in your oil.


Should be no need, the oil would have started to look milky if the coolant was leaking into the oil in the first place.



starspangled6.0 said:


> I've been tracking a coolant leak for the past few months... I feel like it was happening last year too, but I always chalked it up to the typical/occasional need to add a splash of coolant to most vehicles. It loses about 1 hash mark of coolant every 2 weeks,


A hash mark every two weeks over two months is quit a bit of coolant to leak into the oil without noticing it!


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## starspangled6.0 (Apr 16, 2016)

^^ very true. No change in the oil when I shined the UV light on it. I'm leaning more towards the cap not sealing properly.


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## starspangled6.0 (Apr 16, 2016)

Just ordered a handful of those oversized 4.5mm o-rings. I'll do another check on the vent tube as well as the water pump this weekend.


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## starspangled6.0 (Apr 16, 2016)

I put on a new 4.5 mm o-ring yesterday. I haven't been driving much this past week so the car wasn't low on coolant; hopefully this new snug-fitting o-ring does the trick. Kudos to the O-Ring Store for fast shipping and including a free piece of candy in my order!


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## Cruz15 (Mar 17, 2016)

starspangled6.0 said:


> I put on a new 4.5 mm o-ring yesterday. I haven't been driving much this past week so the car wasn't low on coolant; hopefully this new snug-fitting o-ring does the trick. Kudos to the O-Ring Store for fast shipping and including a free piece of candy in my order!


Link please. Thank you.


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## starspangled6.0 (Apr 16, 2016)

4.5mm X 23mm Buna-N 70 Metric O-ring [N4.50X023] : The O-Ring Store LLC, We make getting O-Rings easy!


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## Cruz15 (Mar 17, 2016)

Thank you.


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## starspangled6.0 (Apr 16, 2016)

So after a week or so of the O-ring being installed, I see no signs of fluid loss. I do expect the new ring to shrink a smidgen (that's why I followed the advice on this site and picked up a handful of the rings), but so far it appears to be fixed!


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## LulzT1 (Aug 24, 2015)

starspangled6.0 said:


> So after a week or so of the O-ring being installed, I see no signs of fluid loss. I do expect the new ring to shrink a smidgen (that's why I followed the advice on this site and picked up a handful of the rings), but so far it appears to be fixed!


Nearly a month later, any update on this? Mine is doing the same thing. No visible external leaks and it doesn't really smell like coolant. I'll take a pic later, but I'm almost down to the lower hose! I have 68k on my '14. I have not added coolant to this car in its lifetime.


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## theonlypheonix (Oct 8, 2015)

Just wondering whether anyone has used a scan gauge to accurately monitor coolant temps to see whether there is a high coolant temp coinciding with this problem? Has anyone have recorded coolant temps over time, warm up thru extended operation?:icon_scratch:


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## LulzT1 (Aug 24, 2015)

Haven't watched the SG, but it has never overheated and the gauge in the dash is always at 1 tick left of center.


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## theonlypheonix (Oct 8, 2015)

LulzT1 said:


> Haven't watched the SG, but it has never overheated and the gauge in the dash is always at 1 tick left of center.


Is there more to this then on first thought??

With 69K mi on the clock, I would agree mine has never gave an indication of "overheating" and the dash always (except warm up) displays 1 tick to the left of center but... when I hooked up a scan gauge and monitored the coolant temps from warm up thru extended driving of about 1 hr of 65 -70 MPH then following up by cool down on local roads for 2 miles on the way to and from work. One can see that the coolant temperature is quite active or at least on my '15 Cruze TD.

Observation shows that warm up is typical and reaches a steady temp of 192 to 198 for a while then at some point it seems that the temp becomes active and will start rising to 212 and from that point the temp will regulate between 216 and 208 (appears 212F +- 4 F). The higher the temps the higher the system pressure and therefore weak seals will be more apt to leak. Since I do not appear to be loosing coolant and everything otherwise appears normal I beginning to wonder about a weak or defective thermostat? However the thermostat on the Cruze appears to be more of a control (with a heater?), do we know whether the ECM at some point is going into some active state of attempting a "smart" temp regulation other then just simple temp stabilization @ 195 F? This could be kind of like the so call "smart" battery voltage regulation GM adopted but in this case the engine temperature? Or maybe this is just a matter of difference between where the dash gauge senses and where the location for the coolant temp sensor is located, assuming different sensors?


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## Cruzator (Dec 31, 2014)

Not to sidetrack off the OP's point of a coolant leak, but in answer to the above questions on monitoring coolant temperature, I have done this since about 10,000 miles, and currently have 58k. I have monitored the coolant temp with both an Ultra Gauge and currently use an Edge CTS. On flat ground on the highway, I see temperatures any where between 195 and 215. My daily commute requires a climb from 6000 ' in elevation to over 11,000' and back down to 9000'. The temperature really heats up in the summer when pulling the hills. I'm always at least at 227 and have seen as high as 235. It appears the shutters open at 218-219. This will keep the temp from climping high if it's not a steap grade. The fan, according to my CTS, starts kicking on at 213. By 230, it's at 50% speed. I've never seen it go past 60%. The time I hit 235, I was trying to get it hot to see when the engine temp gauge would move off it's normal position, 1 tick under half. It never budged. I personally don't like it over 215, but there isn't much I can do about it and I'm used to it my now. I typcially don't have the AC on, but it doesn't really affect how hot it gets, but it does affect how fast it gets there. I've had it hit 225 when it's only 30 degrees outside. EGT's are close to 1000, if not slightly over during the pulls. I've heard people talk about the message on the DIC (AC OFF DUE TO HIGH ENGINE TEMP). I'm not sure how hot that is, but it must be quite toasty!


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## starspangled6.0 (Apr 16, 2016)

I'll have to check it soon after a Gulf Coast-to-Canadian Border road trip I took last week, but I didn't see any lowering in the time before that.

Regarding coolant temps: the delete\tune made a dramatic difference on the engine temps. It takes much longer to warm up, and usually reads 1-2 ticks cooler at freeway speeds than it did before the modifications.


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## Rawhp88 (Sep 25, 2017)

Just saying hi and obviously New here had my cruze since January 15 and now 108k on it. Me too has had this issue and been Following this form for some time. Dealer and I can’t figure out the slow leak but is also getting worse over time. Have replaced thermostat and water pump also New cap . And the oil isn’t milky. Anyway just wanted to say hi in the diesel section.


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## starspangled6.0 (Apr 16, 2016)

No milky oil, but I discovered that the overflow tank was half empty again. The o-ring was quite gummy and nasty from various coolant particles, but I'm suspecting that if it is leaking from the evaporation action again, it's because I installed that o-ring at 90* and 95% humidity, and now I'm living where it's 35* and 15% humidity.


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## dougc905 (May 24, 2015)

I just spent $2400 on a new *egr cooler* -the tech said that it had developed a crack and was leaking coolant into the engine. So my car was in fact burning coolant. After all of that was replaced it then threw a def quality error. In response to that, the tech cleaned to nox sensors. He thought that perhaps the coolant had fouled a sensor. I haven’t had a chance to drive it far since then so cannot report on the result of cleaning.


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## LulzT1 (Aug 24, 2015)

Picked my car up from the dealer, they just topped off the coolant, I don't think they gave it any attention. I don't see any leaks, so I guess I'll continue to watch it.


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## LulzT1 (Aug 24, 2015)

LulzT1 said:


> Picked my car up from the dealer, they just topped off the coolant, I don't think they gave it any attention. I don't see any leaks, so I guess I'll continue to watch it.


Bump. A little over a month later and I'm down to the second to last tick mark. Pretty alarming to lose the much coolant in a little over a month ! Haven't noticed any puddles under the car. Maybe add dye if I can source some locally.


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## jakenkaiser (May 17, 2017)

I had the same issue. It was the coolant pump. Sometimes when shutting the car off after a more "aggressive" drive , the pump will slightly leak due to the temp+pressure in cooling system. Then next drive there will be no leak because the pump is running and the coolant is flowing. I had my water pump and timing belt replaced under warranty at 95k, no more slow loss of coolant Currently at 101k. 
Hopefully this helps


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## HarleyGTP (Dec 14, 2013)

I'm going to bump this thread up. I've replaced my water pump, thermostat and reservoir cap and can't find this **** leak! I can smell the coolant when I get out of the car after a drive or if I'm sitting in traffic. Has anyone had any luck locating these leaks?


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## sailurman (Sep 29, 2016)

Transmission coolant lines?


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## sailurman (Sep 29, 2016)

https://www.cruzetalk.com/forum/201...ussion/241027-coolant-leak-behind-engine.html


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## HarleyGTP (Dec 14, 2013)

Replaced those coolant lines going to the oil cooler a few weeks ago and also the oil cooler itself. 

STILL getting the smell of coolant!!!! This is so frustrating.


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## sailurman (Sep 29, 2016)

Pressure tested the system yet?


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## HarleyGTP (Dec 14, 2013)

sailurman said:


> Pressure tested the system yet?


That's next on the list.


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## [email protected] (Mar 16, 2017)

Have you checked by the EGR valve? Maybe one of the gaskets is failing causing a leak.


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## MRO1791 (Sep 2, 2016)

HarleyGTP said:


> Replaced those coolant lines going to the oil cooler a few weeks ago and also the oil cooler itself.
> 
> STILL getting the smell of coolant!!!! This is so frustrating.


My 2015 had a similar very slow leak, just a hint of smell. Dealership never could find it, and it still has the UV dye added. After a while it appears to have stopped. Have not seen any further loss of coolant, nor smell. 

Sent from my Moto G (4) using Tapatalk


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