I know, I have seen this thread before, but I wanted some feedback before I replace the booster (and cram myself under the dash) on my sat-in-my-uncle's driveway-untouched-for7-years '88.

I have a very hard pedal, and I have read in the forum that it is most likely the booster. I checked the check valve to see if it is working (inhaled lots of gas fumes, yummy); it is. Can't get it off the booster though. Vacuum tubes seem ok. Replaced rotors, pads, brake lines from body to caliper and fluid. The calipers all open and close fine, except the passenger front, on which the pads aren't pulling away from the rotor enough to let it spin freely. I can spin it, but there is quite a bit of friction there (could that be my problem?)
I also have the anti-lock light on in the car. Is it possible it is an ABS system problem causing the hard pedal? Either way, how do I troubleshoot the ABS system?

The below link provided interesting reading. After inhaling gas fumes, it made me wonder why there isnt a charcoal filter on the vacuum line since apparently gas breaks down rubber over time. If anybody's vette of this vintage has one, please let me know where to get it. This also mentions injectors. I have no idea how to know if the injectors are operating correctly.

http://cardone.com/english/club/Prod...%2050-0003.pdf

Thanks in advance for your help.

 

A booster would give you a soft pedal. I've read that alot of people with hard pedal issues reset the ABS and it went away.

I would give that a try first. Also bleed the brakes and inspect the hoses.

 

New pads and rotors might cause the additional friction on the front wheel you feel. Other that a bad caliper that would restrict the movement of the piston, the flex if clogged can hold a caliper tight. But sounds like with the work you did you have already bleed the system. If you got fluid out of the caliper the flex line is probably OK. Did all 4 wheels bled properly?

All things being considered and having a hard pedal, the booster is bad. The booster does not give you a soft pedal. A soft pedal would be caused by a master cylinder and that’s not the problem that you have indicated (other than air in the system).

If you can push on the pedal with the engine running and hear a whoosh or a vacuum leak sound, that would indicate a bad booster.

I would normally say, treat the ABS light as another problem.

Now for the big BUT. On those early cars there were lots of cars on the Forum with similar problems you have (few years ago). Hard pedal and wheels locking up. Several ABS pumps were clogged and changed which corrected the problem. If you open the bleeder (on your bad wheel or another) and the pedal does not drop (stepping on it), then it may be the ABS pump.

 

Thank you both for your replies.

pcolt94,

You are right, in that the system has been bled and I replaced the front brake hoses as well (with stainless braided). During the swap of the hoses, the brake fluid dribbled out the whole time, so I know there is no restriction in any of those lines.

I am not certain what to listen for on the booster. I really dont hear much of anything, partially since the engine is so loud.

I went out and ran a couple of tests: the pedal sounds and feels the same whether the vacuum hose is on or not (with or without the engine on). The engine at idle is pulling 15 in hg in the tube that runs to the booster, so i know there is no vacuum leak upstream. Whether that is enough vacuum, I dont know.

It sounds to me like this is leaning towards your ABS pump diagnosis, but if the pump is clogged, would I have free flowing brake fluid out of the bleeders still?

 

Thank you for the correction. These long 12-13 hour nights are wearing on me.

Brycero - Try sticking your head down by the brake pedal and put the pedal with your hand. You should be close enough to hear anything then. If you hear a hissing, then the booster is bad.


Try resetting the ABS pump first. There is an old thread that keeps coming up every now and again about that with a TON of information in it that addresses a hard pedal issue, similar to what you have.

Edit: Here is the link to the thread: http://forums.corvetteforum.com/c4-t...n-finally.html

 

I have read through that one before and got so lost and confused because everybody and their dog was piping in with all sorts of years and problems. I searched for an hour about how to reset the ABS in an 88 and never found it. Can you recall how to do that?

 

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....just left you a response to your PM.