BobbyT

It's almost time to flush the brake system on my 993 again. Is there a DIY way to ensure complete flushing of the ABS, without special equipment?

geolab

there is no trick to it in the carrera 2 without ABD.
In the C2, there are (one channel) three lines of brake fluid going out of ABS unit, one for each front, and one rear, split into two just before the engine..
Some pros tell you to activate ABS through the pedal after first flush, and re-flush, Wrong...
1st, When ABS is triggered on skiddy surface, you cannot control which wheel, thus which channel activates, and...
2nd When ABS activates on wheel, the oil being pressurized to the caliper does not flow anywhere but from the ABS unit to the caliper. It is just being pumped a little to press the brake pads and returns back as if you released the brake pedal. unlike the dual circuit boosted system.
you would want it to go out and never come back, so yo have to trigger the solenoids, whilst flushing the caliper...
and there is no ABS bleeding in the PST2 for C2.
you could check the system but you cannot actuate the solenoids
regards

David in Chicago

George -

What if C2 with ABD?

Thanks and regards to all.

BobbyT

Thanks, geolab. Very clear and useful information. To confirm that I understand fully:
1. No need to take the car to a shop with PST2--they can't bleed them any better than I can at home, true?
2. Should I be concerned with the waxy residue that builds up the the brake system?

911Dave

David, ABD is only on the C4, C4S and Turbo.

Bill Verburg

That's not true at all.

ABD is a part of the M220 option and was available on rwd 993

Included is
LSD
4 channel ABS
ABD

you can flush the brakes on these cars w/o a system tester but to do the ABS unit itself you need a "Hammer" or other factory tool. AFAIK Durametric and the ,like won't do it.

BobbyT

Hi Bill,

Thanks for joining. So, on my 1995 C2, would the Hammer or PST2 activate the ABS and flush it completely? I do have option code 220, and the window sticker shows "torque limited slip with ABD".

I'm a bit paranoid on this waxy stuff that builds up in the brake system. I flushed my brakes and clutch slave when I got the car 7 years ago, and I had to remove the bleed screws to get anything to come out, even with considerable pressure. Then the first thing I got was like beeswax. They have been easy to bleed each time I've done it since, at two year intervals.

geolab

For C2 WITH ABD
YES, in the PST2 you go in ABS 5 / system test / bleeding if you have the M224

the whole procedure is explained thoroughly in the Workshop Manual.
remember eye and butt protection. Secure bleeder hose since Pressure is huge.
unfortunately I could have sent you the PST2 if shipping was not overkill.
regards

BobbyT

Thanks again, geolab.

911Dave

Thanks for the correction Bill. I just bought the Durametric setup a couple weeks ago and can confirm that the ABS/ABD drive links aren't supported yet.