For Teves enthuisiastics

[Guest wally888]

90 pedal still won't return to proper place after depressed/released. About 3/4" low. Can manually lift w/ toe to engage TCC.

Talked to man at Prior about the possibility of a broken spring, binding, etc. and he said fluid pressure actually returns pedal ........mentioned an "O" ring in resevoir...........

I have no idea of what he speaks as I have never seen a disassembled system or removed/installed one!

Any ideas?

[Barney Eaton]

Attached is a layout of the system at rest. I have never seen an exploded view of the master cylinder, probably because parts were never available from GM to repair the unit.

The goofy thing about the unit is that pivoting device connected to the pedal rod on one end and the control valve on the other.

Notice when you push the pedal that lever will allow the control valve to shift back. That allows full pressure to fill the cavity where the lever resides and give full pressure to the rear brakes .... if it were not for the proportioner valver that lives at the junction of the rear lines, on top of the rear suspension.

[Guest wally888]

I am hoping someone who has a spare Teves, has one pulled/removed or....could tell me if the piston arm has any particular position? Pushed in, it remains pushed in w/no fluid pressure to push out? Or does a spring return it to the out position?

[Ronnie]

Wally you must have talked to the wrong man at Prior. There is a spring that pushes the pedal back up. It can be plainly seen on the actuator rod that connects the pedal to the master cylinder in the photo below.

[Guest wally888]

Ronnie,

Thanks! Great pic. Now if I can position myself to see the spring?

[Jim]

Wally,

You sent me an email but I didn't get a chance to reply before seeing this thread.

DO NOT TRY AND REMOVE THE TORX CAP ON TOP OF THE MASTER CYLINDER NEAR THE FIRE WALL.

This what looks like a cap or plug is actually attached to the pivoting device Barney refers to. The cap can be taken out but the brake rod needs to be pushed in part or all the way. If you try and remove the cover/cap without pushing in the rod you will break off the pivoting piece.

The holder that keeps the spring in place is pressed into the mounting assembly that holds the master cylinder to the firewall. Without looking I am guessing, since the spring cannot come out of its holder, that the holder has come loose. I doubt the spring would break either. The spring holder is the anodized part around the spring and it is pressed into the aluminum mounting.

Unfortunately to fix the spring problem you will have to take the whole unit off the firewall removing the 4 # 15 bolts under the dash and disconnecting the brake pedal and then replace the mounting as pictured.

You may be able to pull the ABS unit far enough forward in the engine compartment to change the mounting but you may also have to disconnect the three brake lines at the bottom of the valve body to get the unit far enough from the firewall. In this case you can change the mounting on the bench.

I have the one pictured and can send it to you.

A simpler way might be to try and add a spring under the dash somehow.

Edited May 29, 2010 by Jim (see edit history)

[Guest wally888]

Thanks Jim,

From what I have learned:

Will disconnect brake pedal to see if there is a possible binding. If not I will explore placing a spring on the pedal arm then attaching other end to something under the dash.

[Jim]

I forgot to mention in my other post you cannot see any of the spring and spring holder because there is a boot that covers everything. To get the boot off you have to remove the unit from the firewall

[Ronnie]

Jim, It looks like, in the photo you posted, that the actuator rod screws into what appears to be a nut at the end of the spring.

I believe the pedal not making contact with the switches was Wally's original problem. Is it possible Wally could disconnect the rod from the pedal and screw it out of the nut some to lengthen it? If he could, maybe the brake pedal would go back far enough to make contact with the switches.