I am trying to help a good friend with his Z34. 178K, 3.8L, I would say maintenance has been "marginal". Example, I know for sure the brake fluid has never been changed.

The problem is all 4 brake calipers are locking up. not the park/emergency brake for sure, I even released the cable to be sure.

what we have done:
1.) replaced the turn signal switch & brake switch to cure the no- taillight problem.

2.) reset the ECM & ABS computers

3.) unpluged the brake booster vacuum line to release the pressure, then reinstalled.

4.) unplugged the (2) top plugs on the ABS modulator unit.

5.) unplugged the vacuum line again & the ABS computer under the ABS modulator.

after each test we would drive the car.. it would take about 7 miles for the rears to first start to freeze, then eventually the fronts. It takes literally 3-4,000 rpm of throttle off idle to get the car to move & stay moving. The problem just started out of the blue on Sunday afternoon on his way to my house (10-12 blocks in the neighborhood) to do the turn & brake switches.

We just did step 5.) above... we disconnected the battery as well. then he will drive it again...

Thoughts? master cylinder? brake booster? ABS modulator? ABS Computer? Fluid/debris contamination in one of the hydraulic components? I know for certain it is hydraulic-related. Either the booster is keeping the fluid bore pressurized, the ABS system is slowly applying more & more pressure to the lines, or some combination there of.

I've never encountered anything like this in all my years as a mechanic.

Thanks in advance.
Rob

 

man that's gotta be a computer problem huh? *bump* for someone smarter than i

 

mmm i aint really to sure on that just make to check the wheel berings its a common problem with the 5th gens. It might be frozen

 

well.. the owner had another friend come over while I was not available. They basically put fresh brake fluid in the MC and then bled the ABS module until the MC had fresh fluid in it. whatever it was basically was debris in the ABS module. simply flushing the ABS module & MC reservoir. the problem gradually went away.

the owner plans to take it & have all the fluid completely replaced & the entire system properly bled.

I had heard for years, ASE mechanics talking about how important brake fluid changes are in ABS cars. Now I really believe them. I am having my wife's Mountaineer replaced this next week.

Oh & one thing, finally, that I LIKE about GM cars (lol) is that the ABS Module has actual bleeder screws on it. I had never seen that before... VERY helpful on a problem like this.

 

I had to replace the rear calipers on my 98 Z34 not too long ago. I changed the back brake pads, and I couldn't press or turn the piston back into the caliper so I replaced them. the dude at Autozone said these particular calipers are notorious for "dragging" the brake pads on the rotors. the front brakes were easy. I pressed the pistons back into the caliper with a big C-clamp. long story short...do calipers. maybe the pistons aren't pushed in.

as far as the no tailight problem, check the fuse

 

thanks for adding to the discussion, your findings may help others.

the tail light/brake light problem was the turn signal switch. all fuses & the actual brake switch on the pedal were checked/replaced. the weird thing was the 3rd brake light "cyclops" worked no matter what.. it must come directly off the brake switch.

the issue has been confirmed as debris in the ABS module. a caliper sticking would be a random 1 at a time thing. All 4 calipers sticking at the same time? the probability of that is less than me winning the lottery & I don't play.. lol..

 

Brake Repair Advise Hi,
I have to take my wife's car in for new brakes this weekend. I dont have the time or the know-how to do it, but it needs to be done. They were squeeking for a while and now, every now and again, you can detect a grinding noise. Anyhow, I've heard that a lot of mechanic shops and brake shops rip you off. Is there anything I should look for or be aware of so I dont get ripped off? About how much do you think it should cost, assuming there are no major problems? I live in Dallas and the car is a 2004 Chevy Cavalier. Thanks for any advice.
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which model of 2004 Cavalier? do you know it has rear drum brakes & front discs right?

how does she drive? how many miles on the car? has it ever had brakes done? if the brakes have never been done, I am guessing you have 70,000 or more miles.. hold on to you wallet, you're going to spend some cash.

Where in Dallas are you? shoot me a PM... maybe I can help save you some cash.

just brakes here in Dallas advertises $99.95 for all 4-wheels (pads or shoes, turn rotors/drums)... so $100 incl labor is the basic starting point. (good pads/shoes from Autozone are $45 for the set F&R)

from there it stacks out like this, I used Autozone.com to get basic pricing:
Front calipers $15.00 ea (x2)
Front Rotors $19.00 ea (x2) up to $89.00 ea (x2)
Front hardware $10.00 ea (x2)
Rear wheel cylinder $43.00 ea (x2)
Rear drums $43.00 ea (x2)
Rear hardware kit $15.00 ea (x2)
total parts: $295+ tax

I would guess labor for all of the above to be about $150-$200 including bleeding the brake system.

If you have heard grinding, most shops will try to tell you you need new rotors/drums. If they do ask to see the part & have them measure it for you in front of you. Have them show you the spec, in writing to verify it is out of spec.

now remember you have to add the original $100 for the pads/shoes. so that's $550 + tax on the parts. With a 2004 the brake hoses should be fine.

Rob

 

follow up... one thing you should consider, especially if it has ABS, is to have the entire system flushed. Its probably never been done. I understand that if the repair bill is high, adding on additional services is scary, but like my original post turned out.. its cheap insurance now... or pay for a $400 ABS module later... ouch.

Also, if you do need front rotors, its a good idea to have the front bearings replaced instead of using the exisiting bearings. you're in there... they have 70K+ on them.. safe insurance. the front brakes/bearings handle well up over 80% of your braking.. there are lots of loads on them.

Rob