Brakes
Thread Starter
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
Brakes
My 1985 is now having a brake issue. A hard pedal and the front tires lock up during milady aggressively stopping. It has good vacuum in the master cylinder and the fluid is OK? Any Ideas do i need a new purporting valve?
any ideas on this?
any ideas on this?
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
you don't have a proportioning valve. you have a 2 stage master cylinder.
Try flushing out the fluid by opening the front wheel bleeders and pouring in fluid from the top.
Don't let it run dry, or you will have to actually bleed the brakes.
When the fluid turns clear on the front bleeders, do the rears.
It sounds like the fluid is contaminated, and the contaminates are in the two stage valve in the master. After all, it is over 25 years old if it is the original.
The real cure is a new master cylinder and four wheel flush with all new fluid.
If you replace the master cylinder, bench bleed it, and then hook up the lines, have someone stand on the pedal, and with light pressure on the pedal, crack the lines and get rid of most of the air. The little bubble that is in each line will find it's way out of the master cylinder once the fluid heats up, and the expansion of the fluid will drive the bubbles back to the reservoir.
Try flushing out the fluid by opening the front wheel bleeders and pouring in fluid from the top.
Don't let it run dry, or you will have to actually bleed the brakes.
When the fluid turns clear on the front bleeders, do the rears.
It sounds like the fluid is contaminated, and the contaminates are in the two stage valve in the master. After all, it is over 25 years old if it is the original.
The real cure is a new master cylinder and four wheel flush with all new fluid.
If you replace the master cylinder, bench bleed it, and then hook up the lines, have someone stand on the pedal, and with light pressure on the pedal, crack the lines and get rid of most of the air. The little bubble that is in each line will find it's way out of the master cylinder once the fluid heats up, and the expansion of the fluid will drive the bubbles back to the reservoir.
Last edited by coupeguy2001; Jul 12, 2012 at 06:21 PM.
Suckin' gas, haulin' ass.
Joined: Apr 2010
Posts: 1,100
Likes: 8
From: Newport News Virginia
You don't do the front bleeding first, then the rear. Typically you do RR, LR, RF, RR. Starting from the farthest from the master cylinder working to the closest. I would consult the FSM to make sure you are bleeding in the right order.
I know people have had ABS problems resulting in a hard pedal. I do agree though, try bleeding first. I have suspicions that this will fix the problem though.
I know people have had ABS problems resulting in a hard pedal. I do agree though, try bleeding first. I have suspicions that this will fix the problem though.
