Weak Brakes

[tyly]

I've been having problems with the brakes in the vette. I have bled them several times, but i am still getting hardly any pedal. When i go to slow down, i have to slam the pedal the way to the floor and it takes a while to stop too. I just put a rebuilt master cylinder in last spring, so i dont know if that could be the cause. The propotioning valve is good to, i kno thats a common cause. Anyone else have this problem or know how to fix it?

Thank you!
-Ty

 

[waterboy1976]

Corvette brakes are a pain in the arse to bleed...Mine took several trips around the car....did you do them in the right sequence? RR,LR,RF,LF...outer screw frist on RR then inner.....etc etc...??? Use a power bleeder is available.....it will help speed up the process...

AND WELCOME TO CAC!!!!!!!

 

[tyly]

Thanks for the welcome!

Yea i bled them in the correct order. I was lookin around under there and i think i may have found the problem. I added a union in there and that may have let a little air in. When i get to mess with it, i'll let ya know if thats wat the problem was

 

[petes74ttop]

The information in the Haynes Repair Manual is "Incorrect". They say to start at the left rear- that is wrong!
If you look at the Corvette Shop Manual (1966-1982) on page 10-2 under "Bleeding system" they say to start at the wheel closest to the master cylinder. that means LF RF LR RR>
Here's a quote from my 1974 Service Manual Page 5-18 under "Sequence for Bleeding" "The correct sequence is to bleed the valve, either front or rear system, nearest the master cylinder first. This sequence expels air from lines and calipers or wheel cylinders nearest to the master cylinder first and eliminates the possibility that air in a line close to the master cylinder may enter a line father away as it is been bled"
Hope this helps. PG

 

[GTR1999]

A motive bleeder is well worth the $60 cost I would get one. Also look at the rotors, do they still have the rivets in them? If not someone was in there and chances are the rotor runout is out of spec. Book says up to .005 is ok I set my jobs to .002 or under. Also you need to check the bearign endplay it should also be .0015-.002" You may get by with .003 but anything over that is pushing it and you will continue to draw air into the system as a result.

 

[KOPBET]

Since the front and rear are on different isolated systems, I would think it wouldn't matter whether or not you started at the front or rear ???

 

[Hib Halverson]

I've been having problems with the brakes in the vette. I have bled them several times, but i am still getting hardly any pedal.

(snip)

Before I'd continue to try and bleed the problem away, I'd remove and inspect all the brake calipers.

The 65-82 brake caliper is prone to air leaks. If you have not replaced your OE calipers with stainless steeel sleeved calipers, I'd do that first. Vette Brakes and Products is a good source for that.

Once you install the sleeved calipers, then bleed the system. Since you're starting with dry calipers, you'll need lots of fluid. Also, this is best done with a pressure bleeder. And, you need a container with a lid and a hose to connect to the bleeder. This prevents air from sucking back into the caliper.

Start by jacking the back of the car up, supporting it on stands and removing the back tires. Open both bleed fittings on both rear calipers and let them "gravity bleed" until you see fluid dribbling out.

Refill the master.

Foot bleed or pressure bleed both rears, the left first and then the right. Rap on the caliper body with a medium-sized plastic hammer whil you have the bleeder open. Bleed until no more air comes out.

Now jack up the front, support it with stands, then gravity bleed the fronts until fluid dribbles out the bleeders.

Refill the master.

Foot bleed or pressure bleed both fronts, the left first, then the right.

Set the front down, and return to the rear for a final bleeding. Then put the back tires back on. Jack the front up again and do a final bleeding on the two fronts.

Road test.

 

[Evolution1980]

<<< all the text >>>

Here's another one to file away in the tech section!

 

[JohnZ]

Takes one walk around the car if you use a Motive Products pressure bleeder; one-person job, beats any '65-'82 Corvette disc brake system into submission with a high, hard pedal in ten minutes. By the way, your car doesn't have a proportioning valve - that's just a distribution block with the differential pressure switch in it for the warning light on the dash.

 

[76okievette]

John, I take it that the big C Clamp and metal bar are you invention. I have the same bleeder, but have not used it yet, and I did not get the C Clamp set up. Have you had problems with the master cyl attachment tools that come with the kit?

 

[tyly]

well guys... fixed the problem, and the vette already has stainless calipers from the previous owner. So i jacked the back of the car up today, took the wheels off and bled the brakes. For some reason though, i dont recall ever bleeding with the bleeder on the outside of the caliper, only the bleeder on the back. So i bled all 4 bleeders in the back, then did the front, and now i have a lot of pedal... stops great! but it pulls to the right a little when i slam the breaks on, o well, a project for another day. Im just glad I got it all figured out, tonight is my senior prom and im takin the car

thanks guys!

 

[JohnZ]

John, I take it that the big C Clamp and metal bar are you invention. I have the same bleeder, but have not used it yet, and I did not get the C Clamp set up. Have you had problems with the master cyl attachment tools that come with the kit?

I didn't care for the chain-and-wingnut arrangement that came with it to secure the adapter to the master cylinder, so I cut a 6"-long piece of 1-1/2" square aluminum tubing I had from another project and use a 6" C-clamp with it; better seal, EZ on and off.

 

[bossvette]

I couldn't get mine to seal either and did something simular to John but with a piece of 1/8 sheet metal the size of the adapter. I'm got an Idea to use an old top from a master cylinder to adapt to the bleeder just have to work out the details. But the Motive system is the best I have run across.

 

[petes74ttop]

Just to say thanks to everyone for the great information, Tyly got his car to stop and I learned that you can do the front or rear first and it will work. I bought my calipers at auto-zone in Nov. 2000 and had three of them leak. They replaced the calipers and pads each time for free. In 26,000 miles and 6 and a half years I think they were a good deal. Thanks again for the help. PG

 

[Hib Halverson]

Here's another one to file away in the tech section!

Actually, there's more. If you want everything you ever wanted to know about C2/C3 disc brake service see:
http://www.idavette.net/hib/BBfHInet12.htm
and
http://www.idavette.net/hib/BBfHInet13.htm

 

[Evolution1980]

Thanks, Hib!