Search tool down? Brake pump motor runs continuously

[Terry_H]

My brake pump motor is running non stop. Brake pedal seems fine. Is there a way to test pressure switch? Stuck relay? Where is it located? I see 3 on the drivers side fender. Replaced the accumulator years ago, but the symptoms were bad pedal, not what I'm seeing now.

Thanks....

 

[suicide six]

Usually pump motor will not run at all if pressure switch is bad. those accumlators will go at anytime so dont count it out. check inside car for leakage, your pump isnt making pressure for some reason. either bad pump,internal valve body leakage,accumulator,or system fluid level low. Does motor ever shut off w/ ignition on no e-brake applied and no feet on pedal? Usually if pump runs longer than say 20 seconds the fuse-30amp- blows.

 

[QUIP'6']

go with vaccum brakes and s-10 cylinders i can hold 14# on radials

 

[Turbo Brian]

My recent experience was excessive motor run time because of a bad pressure switch. The switch did not allow the motor to turn off when operating pressure was reached.

The easiest test is to swap in a known good switch.

 

[Black Car]

Terry, another thing that you can check for is fluid flow inside the resverior (sp). Remove the lid and with the PM pump running see if there is fluid flow.
If so, the master cylinder has gone bad. BTDT.

Gary

 

[Terry_H]

Terry, another thing that you can check for is fluid flow inside the resverior (sp). Remove the lid and with the PM pump running see if there is fluid flow.
If so, the master cylinder has gone bad. BTDT.

Gary

Thanks for the suggestions, guys.

Gary, So if that black stuff is swirling, it is leaking internally? I'm looking at inky black brake fluid.

Is it time to chuck the whole system and go to a vacuum unit? The gn-ttype site lists a procedure using a tool to determine if the switch or valve body or pump is bad. Is this tool worth investing into?

Here's a shortened version, I didn't want to infringe on copyrighted material.....
A. Check fluid level per Step 2A.
B. Install J35126 tool per Step 2C and test to determine if fault is in motor and pump assembly, pressure switch, or internal booster leakage.

 

[Black Car]

When I referenced "flowing" you can actually see the fluid "bubbling up" in the resverior. If the brake fluid is black then more than likely the accumulator nitrogen filled bag has ruptered or burst. That will cause the brake fluid to be black and you will see small, very thin stuff floating on the fluid.
If the accumulator can't hold pressure then the motor/pump will continue to run.
No, I wouldn't invest into the tool.
Do you have a friend with another Buick that you can borrow his accumulator from? This will answer your question "if the accumul;ator is Bad".

It will only take 10 minutes to swap out the unit and NO you don't have to bleed the brakes when you swap the unit.

Gary

 

[gofstbuick]

First off, you can order a set of brake gauges from harbor freight tools and make the adapter. When it's all said and done, cost is about 150-175. the actual kentmore tool is 1000 plus adapter

Then you can perform the factory PM test (detailed in the factory manual) and diagnose like a factory tech. I suspect that the check valve (that feeds pressure to the accumulator is defective or has some dirt lodged in the sealing surface. GM still sells the MC rebuild kit with the check valve.