trainmankjm

Went to the shop to get new mufflers and had them check the brakes since I noticed the rear reservoir of the master cylinder was empty and the pedal went to the floor.
They replaced both front calipers,master cylinder and bled the barkes. I test drove it and still it had little or no brake pressure and pedal went to the floor and the brake light came on.
I left the car with them so they could work on it tomorrow.
Can't think of anything that would cause this except air in the system. What else could it be power booster? proportioning valve?

Appreciate your inputs.

White79

i had a similar problem with my 79... it turned out to be the vacuum booster.. its a bitch to switch out, the bolts are behind the dash so you have to drop the steering column to get to them.. but judging from everything u replaced it seems like this is the culprit.

SIXFOOTER

so what did they do with the back brakes? Booster will not cause no brake pressure.
A bad booster will make the braked hard, you have to stand on the pedal to stop.
Mushy pedal is caused by air in the system, or MC seal bypassing. With all the new hardware when you left the shop you should have had brakes, sounds like the did a bone job bleeding the system.

...Roger...

You said the rear reservoir was empty-why did they replace "front" calipers? The rear reservoir is for the "rear" calipers.

lucky76

I noticed that too. Front to Front, Rear to Rear, and they
do meet in between.

happiedazs

Generally when one caliper goes, the others are not far behind so it's best to replace all four calipers with those stanless steel jobs. My last set lasted 18 years. Also, each rear caliper has TWO bleed valves and the mechanic must bleed both on each rear caliper --- which is often missed if the mechanic isn't familiar with Vets.

trainmankjm

Thanks for everyones replies.

Turns out the master cylinder they put in was no good. They put another one in and no problem except the replacement one has a different cover type (one wire clamp insted of the original two).
Bottom line $800 new mufflers,two calipers and a master cylinder.

Would have done the brakes my self but, I had the car up on jacks replacing the gas tank and painting the back frame rails most of the summer and needed to get it back on the road.

I enjoy working on it but driving is what it's about.

...Roger...

Trainman-keep a close eye on that rear level-one bale holddown ? Hmmm-I dont know doesnt sound right-can you take pics?

tracdogg2

Are you saying the master cylinder that is on the car now only uses one clamp? Are both chambers the same size or different? It sounds like they put on a master for disc/drum car, i.e. Camaro. If it is then you need to get it changed asap. It will burn up the brakes.
Mike

trainmankjm

Yea, looks like the knuckleheads used the wrong master cylinder. The reservoir for the front is bigger than the rear they should be equal, correct??

Why me??

...Roger...

Yes as far as the opening-the volumn is smaller in rear but the openings are the same.Like tracdog said your rear brakes could be dragging-that cylinder will have residule(spell check) pressure built in for the rear drum brakes on a camaro-make sure your rear calipers arnt leaking since before the back cyl was dry.

tracdogg2

The rear chamber will have a 10# residual valve in it. Definitely enough to keep the brakes applied. Where are you located and do you need a correct master cylinder? I'm quite sure you need a new mechanic. I would ask them why they replaced the front calipers when they clearly weren't the problem.
Mike

trainmankjm

I'm located in Acworth Ga which is north of Atlanta.
I'm going to make sure these guys install the right master cylinder and I'm done with them.

trainmankjm

Re-installed correct master cylinder bled brakes no pedal. Installed rear calipers ( old pistons corroded) bled brakes pedal better but still not great. The car just won't stop like it should. Thinking about replacing the proportioning valve?? Could rotor runout be causing this??

Gasser Vettes

hello, I'm in Marietta, ga. 1st you need to get your $$$ back from them monkeys. Then you need to look at it one step at a time. I work on old C1 and C3 Vettes as a hobby. If you need help email me at eastcobbstables@bellsouth.net

...Roger...

trainman-start over-I know you dont like hearing that but a good bench bleed is very important.I dont know what year you have but these cars are a little touchy when it comes to bleeding brakes.Do a search for bleeding,gravity bleeding "works" you do not "need" a power bleeder especially for 1 car.Here is a recent thread.http://forums.corvetteforum.com/show....php?t=1507458

RATT7

That was going to be my initial thought, master cylinder.