george4

’89, 170k miles, I bought the car new. Very hard brake pedal, takes a lot of pressure to stop car. Happened over night, not gradually. No fluid leaks, brake pads, calipers and rotors seem fine. Cannot hear a vacuum leak. I think it is the brake booster that is the original. If I pull the vacuum hose off the booster I can feel substantial vacuum from the hose, I do not have a vacuum gauge to get an exact measurement. No change in the pedal with the vacuum line on or off. Engine runs rough when hose is disconnected. Seems like a fairly straightforward job from the FSM other than the 2 access limited nuts under the dash for the tie rods. I replaced the heater core so I have some experience upside down under the dash. Seems like I might not have to disconnect lines from the Master Cylinder but rather just unbolt it and push out of the way to remove booster, FSM is unclear on that point. FSM has reference to special tools and a procedure for rebuilding the brake booster but I am inclined to just buy a new one.
Read a couple of threads but looking for any comments from anyone who has done the job on an “89 and/or to critique my thought process.

383vett

It is your booster and you'll have to turn upside down.

Midnight 85

And probably use some profanity.

Matatk

Sounds like the booster. That is one of the first jobs I ever did when I bought my 89. I have a thread with pics if you search for it. I recommend removing the seat.

As far as your question, yes just unbolt the m/c and pull it forward, no need to disconnect any lines. I don't know of any rebuild kits, maybe that was an option years ago. A replacement booster is around $125 or so based on when I did mine.

Matthew

jmgtp

If the 89 is anything like my 94 the booster is plastic. Time + high underhood temps in the C4 take their toll on the seal between the booster halves. It's probably not holding vacuum. The underdash part is a pain, in retrospect I should have pulled the drivers seat to make it easier.

george4

Thanks for the quick replies. I will track down a new booster.

csthews

Before you get a new booster, start the car and listen for a vacuum leak. I could just be a bad hose.

corvetero

Look for a vacuum leak next to the pedalier, if so then go ahead with the booster because the rubber diaphragm is broken.

garys vette

Before you do that I would do this.

Bleed each caliper.

Those stupid black brake hoses fail on the inside stopping all fluid. This gives you a hard pedal. Both my rear ones were plugged completly allowed zero fluid movement.

Everyone that owns one of the models with that Hose should immediately replace them, serious safety issue!

g

george4

Checked that as best as I could. Even used a mechanic’s stethoscope but could not find a vacuum leak in the hose but did notice some noise that seemed to be coming from the booster itself. The end of the hose into the booster was pulling a substantial vacuum when disconnected from the booster so I assuming the hose is good.
BTW, the 2 nuts under the dash were pretty easy to get off. I used a long handle ¼ drive ratchet with 4” wobble extension and a standard 13 mm socket. Little tight but the small head ratchet was the ticket, only took about 10 minutes after I took the under dash panel off. Did even bother to take the seat out. The booster should arrive next week.

Cliff Harris

Years ago I fixed my booster by replacing just the diaphragm. I don't think you can buy those any more.

It is quite common for the booster housing to crack. They usually crack on the lower inside part closest to the exhaust system, apparently from the heat.

It might be educational to take the booster apart and see if the diaphragm is ruptured. Mine had a split about 2" long and it took some looking to find it.

aboatguy

C4 brake pedals seem to have a higher level of effort than other cars, but seem to stop well if everything is in proper working order. Have you ... sat in the car, put your foot on the brake..... while foot is on brake start engine. Pedal should drop a little if it doesn't its probably the booster... (due to your other posts IRT vacuum at vacuum hose).

george4

The FSM does have a section on rebuilding them with reference to a rebuild kit and special tools so it was contemplated at one time but I did not follow up on that. I will perform an autopsy and let you know.

george4

No change in the pedal feel with or without the engine running.

aboatguy

sounds like your in for a little fun... Sorry brother.

Mike

Daredevil95

Same here, had to change my booster a few years ago, it's not that bad of a job but, there's nothing good about it either, although I cursed quite often. There's a lot of sharp stuff under the dash and my hands looked like a got into a spat with a angry cat with sharp claws, it was to tight for me to wear gloves and have required feeling for clips and bolts. Double check the vacuum lines to it, before replacing.

george4

You need to get to Vegas immediately and start betting heavily. I took off the Booster this am and that is exactly what I found.

george4

I took the booster apart last night. Other than the obvious crack in the case, the internals looked fine. I gave the diaphragm a carefull looking over and it seems good as did the other rubber parts. I was surprised how good they looked given the age. Interestingly, the booster was made in Australia.

Cliff Harris

The master cylinder was also made in Austraiia. Girlok, if I recall correctly. I think the calipers also came from them.

This is how I know about cracked boosters (I couldn't see the crack when the booster was in the car because of where it's located):

george4

Looks like a common issue, here is mine.
http://forums.corvetteforum.com/memb...ter-142322.jpg
Made by BCIA in Australia.