Superv

My 79 keeps getting air in the brake system.
Always seems to be mostly in the rears.

you can bleed it and it will be fine until you stamp on the anchors and then bam!! air in the system again.

I've heard this is a common problem.
whats the best fix for it?

jerryp58

Someone can confirm or deny, but can't runout be responsible for air in the system?

Have you had the rotors turned any time recently?

I have also heard there are gauges that can check runout with the rotor on the car.

Also, I believe that one member was successful in getting all of the air out of his system after leaving the rear end of the car raised for a while and then bleeding the rear brakes.

78Vette-SA

I'd agree with JerryP. Ussually if the Rotor is warped or out of whack just a bit, the constant back and forth (in and out) against the caliper piston causes air to enter the system.

lyonsh

C3s have fixed calipers, which are notorious for pumping air into the system, and it's worse the more runout you have (runout is very common on disc brake rotors).

Yes, there are guages to check the runout. They consist of a vise grip to clamo to a convenient point, a dial indicator, and a flexible connection to hold the indicator.

The most reliable long-term solution is to buy o-ring calipers. These seal much better than the original, and reduce the air pumping dramatically.

Superv

I'll have to check the rotors to see if their warped ...
Any Idea how much O-ringed calipers cost?

Barry's70LT1

Superv....

I don't really agree with Lyonsh. This does not deal with the real problem.
Do you treat a headache by hitting your big toe with a hammer ? You do
forget about the headache. (Sorry, I don't mean to be sarcastic, just trying
to make a point).

Rear rotors are so easy to fix the runout. The problem is that most people
do not understand what the problem is, and have no idea how to fix it.
So they buy the O ring calipers that only mask the problem for a while.

Myself and many others on this forum can provide a detailed procedure to
checking rear rotor runout and cost effective repair.

If they only need shimming, then a dial guage, $ 35.00 and some shims
$ 5.00 will "permanently" fix the problem.

I guess my conservative nature says why spend hundreds of dollers to hide
a $40 - $50 fix.

Just my opinion.
Lets here from the o-ring group.
Thanks
Barry

Tom454

Barry is right on target- the o-ring pistons will also fail eventually because the initial cause was not addressed properly. Unless you turn or replace the rotors, you are treating the symptom, not the cause. The o-ring pistons seal so well, that over time, the constant pulsing of the pistons against the bores during braking causes the bores to eggshape. If you remove the rear rotors, be sure to mark them before removal so you can re-mount them in the same place. The spindles and rotors were machined as a set originally at the factory.


[Modified by Tom454, 9:16 AM 1/4/2002]

lyonsh

Well, if I were going to start banging on my toes, I would put on steel-toed boots. :lol:

There's nothing wrong with fixing runout; I do it myself on my cars. But virtually every rotor in existence develops some runout - assuming you drive your car (and if you don't runout isn't a problem). The o-ring calipers have a greater tolerance for runout.

But as Tom says, by all means fix your runout if it's so bad it's "egging" out your caliper bores.

majglc

I had the same problem and it was caused by rear rotor runout. I had the rotors turned on the car and put on o-ring calipers.

Superv

From the general feedback I'm getting sounds like O-ring calipers are a must as well as probably skimming or replacing the rear rotors.
Finally I might be able to drive the car feelling happy that It might actually stop. Thanks for your help guys.
I should be doing a few bits to the car in the next few weeks so I'll let you know how I get on.

Chris