Dope

Hi guys,

So unusual problem started happening with my 99 FRC. Last night when driving home from work, it felt like the car was dragging the brakes (almost like I was driving into a strong headwind). It took more gas to keep the car moving at the same speed. I was trying to figure out what was happening when I realized the brake pedal was really hard. I also noticed that when I touched the brakes at all the car stopped REALLY hard. I could engage ABS with maybe 1/4 brake pedal travel. I started smelling burning brakes so I pulled over. All four wheels were very hot to the touch. The brake pedal was still very hard but if I pumped it really hard a few times (while stopped) it softened up and this seemed to let the brakes go and act normal again. I drove home with no problems.

Today I went to drive to work and after about 5 miles the same thing happened. Car started dragging on the highway. I pumped the brakes a few times but this didn't help. Probably because the brakes would engage so hard I really couldn't do it too much (engaging ABS at highway speeds in traffic is not recommended). So I pulled over again (now with smoke rolling out of all 4 wheels), pumped the brakes hard a few times and it softened right up. Drove home with no problems.

Given that it's all the brakes and the pedal is getting stiff I'm thinking brake booster at least? I've never heard of this problem on any car before. Is there anything else worth looking at while I have the brake booster out? Worth swapping out the MC too? Car only has 40k miles on it, brake fluid changed regularly (it was nice and clear still). Not a parking brake or individual brake problem due to the nature of it affecting all the brakes equally.

Dope

Bill Curlee

Seen this issue before hare on the FORUM and it turned out to actually be a defective brake booster.

See if you can pull the vacuum hose off the booster and plug the vacuum line to the engine and take it for a short drive and see if the symptoms change.

Bill

K-Spaz

I would not have guessed the booster could be at fault, but it would affect all 4 wheels.

The only time I ever saw something similar was with contaminated fluid in the master cylinder, made all the rubbers in the MC swell up and made the pedal rock hard. Needed MC and all 4 calipers on that car since all the rubber parts were destroyed. Nowadays there would probably be a bunch more to fix, but nowadays the silicone rubber orings might not be susceptible to that either. Idk.

If you replace anything that opens the brake lines you might need a scan tool to do the brake bleed.

Dope

Thanks Bill. I have a new booster coming in Friday, should be an easy test at least.

Dope

MAD Matt

I think Bill is spot on. My first C5 was an 01' Coupe that had the exact same thing going on. Fortunately it was still under warranty. The booster was binding causing just what you have described. Good call, Bill. The dealer swapped it out. The thing that I had trouble with is the idiot at the dealership didn't bother to follow proper procedures and used a pry bar to get the booster off and cracked the under try in the process. Step one is to remove the washer tank to give you clearance to get in there so you can pull on it. During assembly the factory uses speed nuts sandwiched in between the panels on the firewall. Once you remove the nut under the dash you are going to have to deal with the speed nut as they are inaccessible. You have to pull and rock the booster from side to side and up and down, basically wiggling the booster out. Hope this helps! Don' t use any pry bars!!

Pounder

I was going to suggest this also, but Bill seemed to know ? I've seen oil change places put other fluids in the master cyl ??

Dope

Swapped out the booster today (what a PITA), will drive it this week and see if my brakes catch on fire or not.

Dope

Paris Hilton's Dog

Hopefully the new brake booster corrects the problem. If not, here's another scenario that fits the reported systems and which is sometimes observed on old motorcycles:

1. Pressure relief port (some call it compensator port) in master cylinder gets blocked by some contamination.
2. When vehicle is operated, heat from brake application raises temperature of brake fluid.
3. Brake fluid expands but pressure is unable to vent to atmosphere due to blocked pressure relief port.
4. Increased system pressure causes brakes to self-apply.
5. Positive feedback loop of heating brakes and increasing system pressure causes braking force to increase autonomously until vehicle is forced to stop.

In this case, the remedy is to insure that brake fluid is always vented to atmosphere when master cylinder piston is in the retracted position. Often this means removing contamination from the pressure relief port but sometimes this can be caused by something that prevents the master cylinder piston from fully retracting.

Best of luck.

bolling

This sounds weird but on my work truck the left front brake was hung up. It turned out that the rubber brake line had collapsed and wouldn't let the caliper release. The mechanic said he had seen it before.

K-Spaz

I have seen that several times, but not on more than one wheel at a time. Of course if calipers were left to hang off the lines that might do it.

bolling

I missed the part about all four wheels, should have read more thoroughly.

Dope

Whelp, drove it twice today, 20 miles each time with no problems. Pretty sure the car is all better now as the problem previously exhibited itself within about 5 miles the last two times I had driven it. $200 and a couple hours of work, not bad at the end of the day I suppose.

Dope