# Strange sound on gas pedal



## sciphi (Aug 26, 2011)

That's the ABS self-check doing its thing. If it happens at about 17 km/h once after starting the car up, that's what it is. It's perfectly normal.


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## spacedout (Dec 7, 2010)

To me the ABS self check sounds like you are scraping the bottom of car going over a speed bump or pulling into a gas station. Only happens first time you hit 12MPH every time you restart the car.


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## NickD (Dec 10, 2011)

ABS has been doing this dynamic self check for years. When you first switch on the ignition, a static test is done, just checking for opens or shorts. If the light goes off in about a second, you know you don't have that kind of problem.

Vehicle has to be moving to compare the pulses from the wheel sensors for equality, happens at 8 mph. If your ABS light goes on, could be a wheel sensor problem, but not an open or a short. Also fires up the ABS pump motor for a current check, that is what causes that vibration you feel.

If you hit the brakes where one wheel has about 20% more traction than the wheel on the other side, will also feel that vibration. But that is rather rare after an icy rain where the entire road surface is glare ice. No difference in pulses, so no ABS, you won't feel any vibrations, period.

It's for this reason, I feel ABS is worthless, but its the law. One thing ABS does do, is gives you reasons to get a second mortgage on your home if you have problems with it.

A big flat lie with ABS, they say that ABS does not interfere with normal braking, nothing further from the truth. Each caliper or cylinder has a valve in the ABS modulator that is suppose to pulse about ten times per second if ABS is called for. These valves completely interrupt the fluid flow. If a made in China pulsing transistor shorts out, that valve will completely close and you will have zero braking with that wheel. Not very likely, if all four short out, you will have zero braking.

Another cause, is after all these years, brake fluid is hygroscopic, that will gum up and cause one or more of those valves to jam also completely preventing flow losing braking to one or more wheels. In cases like this, nothing electrically wrong, so the ABS light won't even come on.

Some Stanford University professor on a government grant, forget his name, came up using statistics to say ABS is 14% safer, so therefore the idiots in congress made having ABS is law. Not fun living in a country led by idiots.

Its for this reason, would recommend you flush your brake system at least once every three years. Companies like BMW recommends this be done yearly, GM is dead quiet on this subject. To do this, need specialized equipment the average driver just does not have, so get your credit card out.

Key item is a scanner, practically any generic scanner does not have these features, came its because of liability reasons. This is yet another major contradiction, anyone can go to any auto supply store and do their own work on the main braking systems, and ABS is not suppose to interfere with normal braking.

Also if you hit your brakes hard enough to activate your ABS, you just don't know how to drive on icy roads. Yet another thing, your employer and schools demand you be on time when being forced to drive on icy roads. With delayed traffic, this is when everyone drives like a maniac.


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## obermd (Mar 3, 2012)

I never had to flush my brake system in my Montana. It ran for 10 years with no problems. Although a driver who is really good with threshold braking can outperform ABS, that takes a lot of time and training as well as a car that provides true feedback to the driver. Not only are most Americans only interested in getting from point A to point B they don't want to know how it's done or how to do it more safely. In addition, most cars on the road today give such poor feedback to the driver that it's hard to tell just by non-visual feedback if the car is on slick road or dry pavement in some cases. Non-visual is the key here because driving after dark can hide the visual clues on the road surface.


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## NickD (Dec 10, 2011)

While slightly off topic, my wife really loves those fog lamps I added, questioned me at first, now can't live without them.

On the main topic, will stick with my flushing, one trick is to hot wire the ABS pump to avoid laying out 5600 bucks for a GMTechII scanner with an ABS module. Was able to save one modulator by flushing it out with denatured alcohol, blowing that out, then flushing again with brake fluid. Using a pulse generator with a power transistor driving those solenoids gives a means of testing those.

With module, the electronics, reason why they put that do not open label on it, is they don't want you see see the five bucks worth of parts that robbed you blind for. Typical to find very poorly soldered connections, use a curve analyzer to determine the type of transistor used. One of the four have to be good. 

Wheel sensors can be of two types, either a coil of wire or a Hall Effect transistor, also can be replaceable types or integrated with the hub. Had the latter, killed me to pay for an entirely new hub just to get a new two cent coil of wire. I did break open the old one, idiots never protected that coil with either a piece of tape or silastic. With the epoxy embedded into that coil thermal expansion broke those very fine wires. 150 bucks for this POS.

Yet another problem is never find a single cable going from the module to each wheel cylinder, but a series of connectors buried in hard to find places. When I find those, dump those cheap connectors and hard solder those. Its not like my electric drill that I am always plugging and unplugging every five seconds. With ABS cables would never be doing this job again.

Then insurance regulations, if they inspect your vehicle in the event of an accident and your car does have ABS, they better be working, or they can deny your claim.

Yeah, always find people slide through either stops signs or traffic lights, in particular with 4WD vehicles. They think because they have 4WD, they have better stopping traction when all vehicles have four wheel brakes. And those big stubby tires are far extra worse on roads. Always have to use extreme caution when crossing intersections, or would end up with an SUV on my lap.


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## jblackburn (Apr 14, 2012)

Bleeding ABS Brake Systems

The car I owned with ABS didn't have any "hidden passages", and the ABS pump only kicks in when you need it. Otherwise, it brakes just like a normal car.

I betcha most systems these days are designed to be fail-safe like that, not with a valve that gets stuck or doesn't work without the ABS system active. That sounds like an old engineering oversight that has probably been fixed.

In fact, I can pull the fuse for ABS and I bet the brakes will all work just fine. It did on the Volvo and Toyota I used to own.

The only thing prone to failure in the Cruze's system is the vacuum pump for the brake booster. This has been on many cars since variable valve timing was introduced (these engines provide little vacuum at a high idle in the morning). If that goes out, you just have to manhandle the brake pedal like you're driving a truck. So...about like my Bug.


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## tavogl (Jun 24, 2013)

Hi and wow. I cant believe it. Yes it only happens once when I start the car and might be around that speed ill check it later, wow I was going to go to the car dealer for this, I think they should have told ke. One more thing, is this on the owners manual? And many thanks for all your quick answers! You guys are awesome

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## NickD (Dec 10, 2011)

Actually in this case, its that turbo causing that low vacuum problem. Really don't get much vacuum with a 15 psi boost.

In not the good old days, vacuum operated windshield wipers were used, try seeing the road when driving up a hill. Did come out with a dual diaphragm fuel pump, upper was for a vacuum pump. But really didn't help that much, just a little.

Did waste some time in the late 90's designing a dual output alternator system. The guys design electric bulbs, the incandescent types want to stick with 12 V, at 48 V, filament would be so thin, would break with the first bump on the road. Dana wanted the 48 V for electric brakes, was very confident at first, but decided they nor anybody else could design a reliable electric braking system. So the entire project was dropped.

But electric windshield wipers are really nice.

Another question arose, to minimized the use of fluids, why can't AT fluid with the same high pressures be used in the the AT, PS, and braking system? Reason, never been able to design the reliable seals for using AT fluid in braking systems.

Key agency involved with minimizing fluids is the EPA, ease of recycling is their key issue. Even with plastics, demanded we use the same type regardless of the application to make recycling easier.

Took a bit to getting use to electric power steering, but love it, unless it goes out which mind did, hope that never happens to my wife. Not sure what is worse, certainly tired of repairing leaks, electronics may present a new set of problems.


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## obermd (Mar 3, 2012)

jblackburn said:


> Bleeding ABS Brake Systems
> 
> The car I owned with ABS didn't have any "hidden passages", and the ABS pump only kicks in when you need it. Otherwise, it brakes just like a normal car.
> 
> ...


Good point about the ABS having a bypass. My Montana had ABS problems for three successive winters before a Pontiac engineer figured it out but I never lost braking ability. Just the ABS and Versitrack AWD systems.


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## jblackburn (Apr 14, 2012)

> Actually in this case, its that turbo causing that low vacuum problem. Really don't get much vacuum with a 15 psi boost.


That too, but not at idle pulling out of the garage or rolling down the driveway in the morning @ 1000 RPM with your foot off the gas pedal.



> Another question arose, to minimized the use of fluids


Saab designed a transmission/engine combination that shared the engine oil with transmission internals. It actually worked very well...until the time came to change a clutch.


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## Rochas (May 27, 2013)

I only found out by reading on this forum... but yes it would have been nice to have been told about it. I wonder how many people complain about it?


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## AlainSDL (Jun 13, 2013)

haha, I just posted the very same question. . . glad to know I'm not the only one.


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## tavogl (Jun 24, 2013)

Yes lol I was scared

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## NickD (Dec 10, 2011)

Chevy P-30 employees a Hydro-Boost unit that handles both of the power brakes and power steering functions. Very reliable and fairly inexpensive to replace. Wish they used this on cars. Totally lacks any vacuum hoses.


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