braking problem
Thread Starter
2nd Gear
Joined: Apr 2015
Posts: 2
Likes: 0
braking problem
I have a 1975 with a braking problem. This is a recent purchase about 2 months ago that had brake system overhaul, new booster and master cylinder earlier this year. The problem started about 2 weeks ago, brake system seems to lose "pressure" and braking ability after sitting for about 24 hours. If I drive the care very carefully for about 5 minutes with extensive stop and go (braking) the brakes return to acceptable braking ability. The brake fluid remains unchanged and normal level.
Any thoughts?
Any thoughts?
Race Director
Joined: May 2006
Posts: 18,597
Likes: 2,540
the overhaul was only the booster and master, nothing done to the calipers?
do you know if the calipers are stainless sleeved?
do you know if the calipers are using lip seals or O-rings?
start with bleeding the system, make note if any one caliper has more air than any other.
do you know if the calipers are stainless sleeved?
do you know if the calipers are using lip seals or O-rings?
start with bleeding the system, make note if any one caliper has more air than any other.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Drive the car and get the system hot. Then park the car and pull the wheels off. By the next morning if you can see daylight between the pad and rotor, that's your problem. Those pads move a tiny bit when you hit the brake. The oring calipers dont usually have this problem but the squared of sealed calipers do.
While its up on Jack stands, it would be a good time to check run out. A wobbly rotor will push the pads back and cause the same problem, then as they heat up the rotor could have less run out or more.
Then you have knock back. Loose front hub bearings or bad preload in the rear bearings can cause the rotor to move side to side. Again, pushing the pads back.
Good luck.
While its up on Jack stands, it would be a good time to check run out. A wobbly rotor will push the pads back and cause the same problem, then as they heat up the rotor could have less run out or more.
Then you have knock back. Loose front hub bearings or bad preload in the rear bearings can cause the rotor to move side to side. Again, pushing the pads back.
Good luck.
