Brake Hydraulics - HELP!

[benspeeder]

OK - I've got this 1992 968 I bought for parts and the car was just too nice so I've restored it to be a street car - something to beat around in that's the same year and model as my race car.

It sat for 6-8 years. I got it running well and drove around some country roads. Checked the brakes - all four rotors were hot so brakes seemed to be operational. Rotors and pads were just cruddy so I replace with new rotors and pads. Go to bleed the brakes - cannot get hardly any out of the rear calipers. Here's my symptoms:

• Can't get any fluid out of rear calipers - only a spit or two - pedal will not go down with bleeders open

• Front calipers - I can pump fluid through but it takes a mule to push that pedal

• When the front bleeds it feels erratic - pedal won't go, then will drop, next pump smooth, then pedal is rock hard won't move, next pump it'll go down but not smoothly - sorta weird

• Front calipers will function

• Rears calipers do not function with pedal depressed

What I've done:

• Bought a motive power bleeder - this did nothing alone - but it did help when I also push the pedal

• Started disconnecting the rear lines where there were fittings to see if there was fluid/blockage - no fluid at the rear fitting where the lines disappear under the chassis -

• Disconnected the lines at the master cylinder and looped hose back into the reservoir - brake pedal works nice and smooth - fluid moved from both lines no problem

I figure there's a blockage somewhere - not sure if I can run compressed air into the system without damaging anything. I was informed not to run more than 20-30 PSI into the lines.

Can I use the power bleeder to push fluid from the rear back towards the reservoir to unseat a blockage?

Any suggestions on this odd problem?

[benspeeder]

I think I figured it out - the blockage is at the ABS pump. Replacing that with hopefully do the trick.

[Loren]

You will need a PST2 or PIWIS tester to properly bleed the new ABS pump/block.

[benspeeder]

You will need a PST2 or PIWIS tester to properly bleed the new ABS pump/block.

Hi Loren - Thanks for that heads up. Called my local independant P shop - they said install the pump, flatbed the car on down and it's a simple process for them to run through the cycles with their equipment.

Great example of why this forum is so valuable - I'd have put the pump in and bled it and thought I was done.

Thanks,

Ben

Edited April 27, 2009 by benspeeder

[Loren]

You will need a PST2 or PIWIS tester to properly bleed the new ABS pump/block.

Hi Loren - I don't have those tools. Shall I install the pump and bring to a shop or just bring the pump with the car and leave it to the pros?

Thanks,

Ben

I would find a shop with one of those tools. You need to run the ABS pump to clear the air from the new block and lines.