brake expert needed
Thread Starter
Racer
Joined: Oct 2003
Posts: 376
Likes: 0
From: NE PA PA
brake expert needed
I have a 75 vert. When I first got the car, I had to replace the booster and the master cyl. I have always had problems with the rear brakes. I have bleed the rears ( inner and outer) at least a dozen times. They work great for a while, then stop working. I always get air out when bleeding. It has been 2 years of this and I'm at the same point again. I always leave 1/4" of room in the master cyl. when topping the fluid off. But when I need to bleed them again the fluid will be right at the top or even under pressure. Is it possible that the rear brake system is sucking air some wheres and not leaking any fluid? I can not understand how so much air can be in the system and not show any signs of leaking. Please help.
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,502
From: Little Rock AR
The rear wheel bearings could have too much end play or the rotors can have a little runout (wobble) which can cause the pistons to push in and out. This movement can cause air to be entrained (pulled in) past the seals and into the hydraulic system. The fluid will be displaced back to the master cylinder. Common problem with Vettes.
Check the rear rotors for runout and check the bearing end play. If you are out of spec, there is the problem. You can get tapered shims to align a rotor better if it is not running true. You can also reposition the rotor into another one of the positions. The rotors were rivited to the axle flange and then machined as an assembly originaly because they were trying to avoid this problem. Another way to improve the situation is to use O-ring seals instead of the factory lip style caliper seals. The O-ring style caliper is a band-aid for the problem that might help in less severe cases. I have not used the O-ring calipers but many other people on the forum have used them.
I ain't no expert but this should help.
-Mark.
P.S. - looks like I type slow
Check the rear rotors for runout and check the bearing end play. If you are out of spec, there is the problem. You can get tapered shims to align a rotor better if it is not running true. You can also reposition the rotor into another one of the positions. The rotors were rivited to the axle flange and then machined as an assembly originaly because they were trying to avoid this problem. Another way to improve the situation is to use O-ring seals instead of the factory lip style caliper seals. The O-ring style caliper is a band-aid for the problem that might help in less severe cases. I have not used the O-ring calipers but many other people on the forum have used them.
I ain't no expert but this should help.
-Mark.
P.S. - looks like I type slow
