BBGev

i have a slow leak on my 1990 right where the master cylinder meets the booster. ive been rebuilding the car so i havnt driven it much but from taking it down the driveway and up the road and back the booster still feels fine. i know sometimes if the leak is bad enough fluid can get into the booster and mess it up. Im assuming theres a gasket in there i ned to replace but i just wanted to get some more info on this job. Does anyone have any experience with this job? any tips? anything you wish you had done that you didn't?
im also guessing that ill have to bench bleed the master and bleed the lines afterword is hat right?
thanks

7thvet

You need either a new master cylinder or rebuild it.

Jud Chapin

Agree 100%!

topfuel67

On my 92 I bought in October the power booster was bad. I replaced it, not the master. Brakes were great, but I noticed brake fluid leaking between the PB and master cyl. Even dripped down to the ground. I replaced the master and no more leaks. Yes, you need to bench bleed the master. No, there are no gaskets between the 2. Just the seals in the new master. Yes, you need to bleed the system after installing the new master that has been bench bled. You need to bleed it for a long time as this brake system has a lot of lines due to the ABS pump. It is a great way to get all new fresh brake fluid in this system as these ABS pumps are not available anymore. A member posted a link of a unique shop that rebuilds them and they were close to $1000.

colter

Undo the two nuts on the Master Cylinder. Pull the Master Cylinder away from the booster and see if the rear plunger/c-clip is wet with brake fluid. If it is, then you need a new master. One other possibility is if the grommets for the reservoir is leaking, then that could run back and down the booster. I don't know if 1990 has the white switch thing, but that is another place where brake fluid can leak and run wherever. If that is leaking, then you need a new Master Cylinder.