ABS no pump pressure

[Bud Badiali]

88 MArk VII . 90,000 miles

We worked on ABS a month ago for hard pedal, lights on. Replaced pump relay, pressure switch ,and accumulator (used) which got the system to work. Bled them out with all new fluid, cleaned sensors, got lights out and system worked great.

Suddenly one day after 4 or 5 weeks both lights are back on, got hard pedal all the time. Under the hood, the reservoir backfilled to the top with fluid. Can hear pump motor running, but does not seem to pressurize system. Tried another accumulator . Same thing. Opened rear caliper to try to bleed but got no fluid. Took accumulator OFF the assembly, cycled pump and no fluid came out.

Any clues out there? Can the pump motor run and not actually be driving the hydraulic pump?

What to do?

Bud

also at e-mail Specman96@AOL.com

 

[Blasster]

Try this:
Key on eng off, push the brake pedal all the way to the floor board, hard and slow, at least 20 times. It may be tough but do it at least 20 times all the way down. Start it and feel the pedal, if you have pedal test drive it, you may need to do that again even after a day or 2.
Post back results I can always consult some old co-workers I keep in touch with for other possibilities.

 

[Bud Badiali]

ABS pump -no pressure

THanks for responding, I got brave today, took apart the assembly and discovered that although the pump motor was running, but in fact the pump portion itself was broken internally. IT would not draw or pump any fluid.

Could not not get a new pump alone, only a new, complete unit for 1400 (ouch ! )or a rebuilt for 633. (+$100 core)(Prior Reman)

However did grab a break. Found a totalled 92 in the salvage yard with only 70,000 miles and got a pump off it for 15 bucks! Swapped it all works perfect again.

 

[Blasster]

Well congrats on your outcome.Thats the scary thing about MK VII brake systems...Cost. OK that and availability.