In need of a Pontiac brake specialist!

Maintenance/Repairs
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1

I have been having a mysterious problem with my 2007 Pontiac Torrent that apparently no one, not even GM, can diagnose. I have done great research on this problem, and although there seems to be many many folks with Stabilitrak/Traction Control message issues, none seem to be having the same problem I am having.

Problem: After driving my car about 10 minutes, the brake pedal gets progressively stiffer and the car itself is “heavier” (no other way to describe it). If I continue driving, the car will begin to make a low roaring sound, which will get louder and louder if I continue driving. The car also at this point will lose acceleration and it is very difficult to make the car accelerate (that also makes the noise louder). A couple of times (luckily I was in my garage at home after driving), the car was stopped and when I tried to reverse, the car would not move at all.

When this problem first started (about 6 months ago), the Service Stabilitrak and Service Traction Control messages would come on, but I had a part replaced and that stopped (although the car was still having the same problem) until yesterday when those messages came on again. It has been four months since the messages stopped, yet the car was still having this problem during that time.

My remedy to this problem has been to pump the brakes each time I stop (I now take the highway instead of the interstate so that I can make enough stops to do this). I can go about 10 minutes before I have to stop, pump the brakes, and continue driving. This makes the stiffness in the brakes stop and keeps the car from making the noise and having the acceleration problems. The car runs fine as long as I do this.

During this six months, I have been to two different auto mechanics AND the local GMC dealer (at least four times). The parts that have been replaced are: right rear hub bearing assembly, EGR valve, rotors resurfaced, left rear caliper repaired, brake pressure modulator valve, and electronic brake control module. The dealership says they do not know what is causing this problem, and they claim they contacted the technicians at GM and they have never heard of this problem. Can I really be the only person in the entire world that has had this problem?

I feel this is a problem in the braking system. Something is getting hot the longer I drive and causing something to lock up the wheels, but not enough to stop the car entirely unless I continue driving. What stumps me is why does pumping the brakes help, and why are no service messages or warning lights coming on?

Any input or advice will be GREATLY appreciated! Thank you in advance!

2

If it was my vehicle…I would replace all 4 rubber brake lines. I had a GM pickup that did this and picked it up at an auction for very little money. It did the same thing and locked up several times on the way home. The owner said it would. I changed the rubber brake lines and it never happened again. It’s worth a shot.

3

Sounds like the system is slowly pressurizing and causing the brakes to drag and get hot, make noise…Missileman’s suggestion is good, The rubber lines can swell up inside, preventing fluid return to the master cylinder…Or the master cylinder itself is defective, preventing normal fluid return which will pressurize the system and start the brakes dragging…

You might try this…The ABS/Traction control system has a pump that holds brake fluid at high pressure. if you disconnect the electrical lead to this pump, the ABS system will be disabled and the dash warning light will come on. The car will still have standard brakes. If THIS resolves the problem, you know the problem is in the ABS system…“Tampering” with the brake system opens a whole new can of worms and I don’t recommend you do this…I’m just saying it’s possible to do it…

4

If the brake fluid has never been changed then maybe it’s due to aged, contaminated fluid which presents boiling point/compressibility issues and to a lesser degree; maybe a caliper slide sticking.

5

GM has issued TSB PIT4287A.

The steering position/torque sensor can cause the ABS to engage.

A scan tool is first used to calibrate the power steering control module. The scan tool is then used to calibrate electronic brake control module. The vehicle is then test driven. If the steering goes out of calibration the steering position/torque sensor is replaced.

Tester

6

My wild a** guess: the brake booster.

The booster uses vacuum from the engine’s intake to pull a diaphragm forward to assist you in applying the brakes. Vacuum is on the front of the diaphragm and the aft surface is vented to atmosphere. When you let the pedal up, the center shaft should open & close valves to enable the chamber aft of the diaphragm to no longer be vented and the pressures in the chambers fore and aft to equalize.

If the center shaft isn’t operating properly, which could be due to a misadjusted brake pedal/master cylinder rod, vacuum will slowly pull on the forward portion of the booster diaphragm, constantly applying light braking. As the pads heat up and the fluid transfers it throughout the system, the system slowly tightens up.

Abs doesn’t cause brakes to drag. It can only prevent them from being applied. It works by introducing solenoid operated valves into each of the lines. If the computer gets a signal from one of the wheel speed sensors that the wheel isn’t turning appropriately, it sends a squarewave to the associated solenoid, interfering in the brake’s application in a pulsating manner as the squarewave rapidly activates/deactivates the solenoid.

Traction control does, however, use brake application to divert energy to another wheel when needed. You should be able to remove the fuse to disable the traction control system as a test.

I’m going with a bad brake booster as my first guess. Try disconnecting and clamping (to prevent creating a vacuum leak for the engine) the vacuum line at the booster. Your brakes will be hard and require more force, so don’t take any highway trips this way, but it should tell you whether or not the booster is at fault.

7

On the stiff pedal and “heavy” feel, I was thinking just like mountainbike - that it describes a brake booster (and/or check valve problem).

But then the rest of it does sound like the brakes are sticking on, in which case I was thinking about the flexible lines as noted by missileman & Caddyman.

A temporary disabling of the trac/abs for diagnosis purposes is also easy and worth it to see what happens.

8

If the booster valve is malfunctioning as I described, the brakes will be constantly applied As the fluid heats up and the heat is transmitted throughout the system, the fluid will expand and they’ll get “on” even more. That would also account for the noises and the drag as well as the pumping helping the problem.

9

I would have the TSB checked.

10

Thank you all SO SO MUCH for your input! If anyone else has an opinion, please keep them coming. I’m glad to know I was on the right track. It’s ridiculous to me that the technicians at the dealership do not have the forethought to try to figure out what the problem is. If they can’t hook it up to a machine and get a code, they can’t figure it out.

11

Did you ever solve this issue??

12

I have had every one of thiESE same issues OVER AND OVER. first started with extreme shaking in front end. Took to dobbs diagnosed as calipers sticking. Changed those. No more shaking but had the loss of acceleration etc. Took to firestone diagnosed bad master cylinder and power booster. Had those changed (power booster half a half gallon of brake fluid in it although ive never had to add brake fluid) was good for exactly one year to the date started all over again. Oh since a week after I bought the car in 2013 the service stabilitrack/tractuon control would come on randomly. GM dealer said it was the EGR valve…surprised?? But they went ahead and changed it fixed that but only for awhile. However they supposedly did a thorough brake system check. Ended up changing all parts listed above and it STILL does the same stuff. Brake pedal gets stiff (I started pulling up on it) and now I have something as of right now UNKNOWN going on. Turn right and there is a horrible “cracking” sound. I will NEVER buy another GM and that is all I have ever owned. This thing is the biggest POS. And completely changed my opinion on GM. Car never once overheaded yet blew a head gasket. One year last its leaking again. So many other “weird” things have gone wrong with this thing.

13

Has anyone checked your front end for bad wheel bearings yet? That thought is strongly circling my mind as I read your posts. There is often good reason when that sorta thing happens in my head.

Many ways to check for bad wheel bearings, not sure if you need me to list them or not…