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-   -   Can't get front brakes to bleed - pedal stops moving!! (

professor-patrick 08-25-2012 05:10 AM

Can't get front brakes to bleed - pedal stops moving!!
Ok, this is really perplexing - downright wrench-throwing frustrating. I've installed and bled a lot of brake systems and have never had this issue.

Every inch of the brake system is new - this is an almost-finished hot rod. Bench bled the master cylinder, installed, bled the rear brakes, no problems; then moved to the front. Have helper pump up the brakes, hold them, I open the bleeder, just a little fluid comes out without much pressure, and that's it. Pedal won't depress any further to force fluid/air out the bleeder. Pedal is stuck more than halfway up/down. Not getting full stroke of pedal.

Opened both front bleeders simultaneously. Pedal still stuck high, no fluid out of front bleeders. Broke front line loose at master cylinder (attached to rear reservoir) - nothing happens, no fluid and pedal still stuck high. Broke rear line loose, fluid comes out and pedal fully depresses.

Have replaced new master cylinder with another new master cylinder - bench bled, same problem. Pedal sticks high when trying to bleed front brakes.

Removed combination proportioning valve, now have front and rear brake lines separate. Front MC line runs to a tee then to both front brakes. Rear MC line to a single proportioning valve then to tee at rearend and to rear brakes. Simple. Still same problem.

Can't get front brakes to bleed, and pedal sticks high.

This is a power brake system - all new stuff. Have checked movement of rod coming out of booster both with and without engine running while MC was removed - get full pedal and rod movement. Have measured rod movement and MC requirements - they are right on. Have less than 1/16 inch of play between booster rod and MC when together.

Any help is appreciated. Will try just about anything at this point!


67Mustang Al. 08-25-2012 06:18 AM

In my case a "hard to bleed" problem was diagonosed when i disconnected the brake lines from the mc and distribution block, pressurized with air, one line at a time to reveal a reversed banjo fitting on a caliper was skewed and not seating.
If you have bled the rears and cant get full pedal to the fronts,(blocked pedal) i would check each line is flowing freely. If you have full pedal to the rear and partial to the front it eliminates your mc. it sounds like there is a hydraulic blockage in the line somewhere, maybe a pinched or blocked line. I would connect high pressure air to the caliper end of the line and blow air backwards up the lines to check a free flowing line.
Apart from that i cant think of anything else. (free flowing bleed screws)

My neighbour had a power steering "growl" that beat him for two weeks. All lines out, pump out, checked, rebuilt, replaced, no luck.
In the end he poked a piece of wire down the pressure line from the pump outlet and found a small piece of rubber hose "offcut" had wedged itself down the line causing a near total block. That cost him .
Al. Goodluck.

S10xGN 08-25-2012 09:14 AM

When you bled the M/C did you verify fluid was flowing on both ends?


professor-patrick 08-25-2012 09:58 AM

Yep, MC is fine.

timothale 08-25-2012 11:51 AM

line hook up
I have heard that some M/cyl have the front wheels fed from the rear chamber ?

OneMoreTime 08-25-2012 02:02 PM

Is it even possible that a residual pressure valve is installed backwards..???


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