Nelson, thanks for the insight. I also have a TR7&8 and get the two
units confused in name sometimes. I don't lose any fluid and have no
visible leaks. I will pull the rear drums and take a peak. It wouldn't
be the first time I messed something up.
I'll keep you posted!
Jim Henningsen
Kissimmee, FL
75 TR6 (Came in Third place at the All British Day in Winter Park FL -
Can't believe it)
80 TR7&8
Nelson Riedel wrote:
>Subject: Weird brake question # 163
>
>
>| Ok listers,
>| The brake pedal is firm when traveling forward. When I go into reverse
>| and then forward the pedal gets very soft and I have to pump the pedal
>| to get pressure back up. After that all is well until the next time I
>| have to back up out of a parking space. Any ideas? The entire brake
>| system has been rebuilt (calipers, master cylinder, rear wheel
>| cylinders, proportioning valve, hoese) and I am running Silicon DOT 5.
>| I had heard that bad wheel bearing might be cause this kind of thing,
>| but when you go around corners.
>| Thanks in advance
>| Jim Henningsen
>
>Hi Jim,
>
>Loose front hubs (loose bearings) can cause the pads & pistons to be knocked
>back into the calipers causing the brake pedal to be soft the first time it
>is pressed as all available fluid is used to push the pistons out to the
>normal quiescent position. This can be tested by making a sharp turn in one
>direction and then testing the brakes. Then make a sharp turn to the other
>direction and test again. An alternative is to jack up the front and see if
>one or both of the hubs are loose on the axel.
>
>Since it only happens after being in reverse, my first guess would be the
>rear brakes. Something may be hanging up the rear shoes when going forward
>so than they never return. When in reverse, they may let loose and force
>the piston back into the rear wheel cylinder. This then would require more
>pedal the first time the brakes are applied again. The rear brakes would
>also have to be out of adjustment for this to be the explanation. I'd apply
>the handbrake firmly but not hard and see if the problem occurs when backing
>up and then going forward. If the problem stops, the rear brakes need
>adjustment. Also, one is probably hanging and that needs to be
>investigated.
>
>BTW, if you're talking about a TR6, that brass H type fitting below the
>master cylinder is a Pressure Differential Warning Alarm (PDWA) device, not
>a proportioning valve. It's function is to give an alarm if the pressure
>between the front and back is different (proportioned).
>
>Nelson Riedel
>Granville, Ohio
>'68TR250, '76TR6, '70TR6 (project)
|