My buddy has a 92 jeep that he has replaced all brake components except the vacuum. His problem is he has bled them over and over and still cannot get the pedal to hold after they are bled. Could it possibly be the check valve in the new master cylinder letting air in? Any thoughts on this anyone??
new brakes
- Thread starter jeepofino
- Start date
graewulf
New member
beachjeep said:
huh? you bleed the brakes with the cap off, yes the brake system is closed, but the reservoir is not part of the closed system - there are valves that allow excess fluid to flow in & out of the reservoir, the cap isn't airtight either. Only time air in the master cylinder will be an issue is if the fluid reserve (this is what the tank on top is) is low and the valve is exposed to the air, which doesn't happen under normal operation. you can drive the jeep with no cap on the MC at all and the brakes will function, granted you'll slosh most of your reserve fluid out the top, but it can be done. Perfect example: the cap for my wife's MC came off (wasn't put back on tight) - she drove it for nearly a month before we discovered this, and she still had fluid left in the reservoir so no air got in the system and the brakes continue to operate normally - i've never had to bleed them since we bought it.
As for all the components being replaced, i assume you mean the master cylinder, slave cylinderes on the drums, and the calipers on the discs? what about the lines themselves, both rubber and hard? if none of the lines were replaced, this could cause problems..
bad vacuum will cause the brakes to work hard, but once pressed it will hold at the same place indefinitely. If the petal creeps you have a leak, or a bad part.. bad seals in the MC cause symptoms like that.. is there fluid loss?
If your friend tried the normal open valve, press petal method of bleeding, you may want to try the gravity method... takes 2 people - and alot of fluid. have one person put a pan under the brake bleeder, other person is up top with extra fluid.. top off the reservoir, crack the valve. let it run, keep topping it off till you think enough fluid has gone through to replace all the fluid that was in the line. then shut the valve. repeat for the other corners.
redrooster
New member
Use a clear 5/16" or 1/4" polyethylene hose from Home Depot or Lowes and snap it on the bleeder. Run the other end into a clear bottle (water bottle works good) to catch the fluid. The clear hose will let you see if any air bubbles come out with the fluid. It usually takes a while to bleed them when you replace all the components. Make sure you start with the wheel furthest (plumbing wise) from the master cylinder.
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