Trouble Getting Pressure To Brakes
9/11/12
Customer
I purchased a slotted, drilled power disc brake conversion kit for my 56 Bel Aire through a dealer last spring in Charlotte. I have installed the kit and bled it. The rear brakes hold pressure but the front side will not bleed. We have checked everything, pumped the pedal about 1,000 times and even "pressure bled" it. It doesnt seem to have any pressure coming out of the front side of the master cylinder as weve even tried loosening the line at the master cylinder and dont get any pressure. My father is an ASE certified mechanic who has been a gm mechanic for over 30 years and hes as perplexed as I am. It seems as if we have a faulty master cylinder. I looked for answers on your tech page but only got some computer script. If you could contact me as soon as possible that would be great. You can email me back or call me at (336) ***-****. Thanks, Jason
Support
Hi Jason, sorry to hear that you are having this issue. Please follow these steps to identify the problem.
1. Bench bleed the master cylinder (off the car, in a vice). If you do not get a good flow of fluid out of either port, then you have a bad master cylinder.
2. If the master cylinder bled properly off of the car, put the master cylinder on the car and bleed it again using the same clear bleeder tubes. If the master cylinder bled off of the car but does not once it is installed on the car, then there has to be a problem with the linkage between the pedal and the master cylinder. The most common issue is the rod that comes out of the front of the brake booster and pushes the piston of the master cylinder. (NOT the booster rod that goes to the pedal, the opposite side.) This rod is often slightly too long and causes a pre load on the master cylinder. This pre load generally prevents fluid from flowing properly out of one of the master cylinder ports. This booster rod should be almost touching the piston of the master cylinder, but not actually making contact. This is often a very small preload of about a 1/4". If you are unsure if this is your issue, try putting a pair of 3/8" thick horseshoe washers between the booster and master (temporarily) and see if the master cylinder starts to bleed properly.
3. If the master cylinder still pushes good fluid out of both ports after being installed on the car, connect the two lines from the master cylinder to combination valve. Once connected, remove a line that leads to the part of the car you are having a problem getting fluid to.(front or rear) and press the pedal once. Reconnect the brake line while continuing to hold the brake pedal down to prevent air from being pulled back through the valve.
4. If fluid is flowing properly out of both ports of the master cylinder (which we tested in step 2), but not making it through the valve, then most likely you will have to contact us to get a replacement valve. You can try to open the bleeders in the part of the system that is getting good fluid and jam the pedal hard one time. Sometimes this will recenter the valve. Ex. If you are having trouble getting fluid to the front brakes, open both of the rear bleeders and jam the pedal hard one time. Be sure to keep the pedal pushed down until both bleeders are closed.