I get a lot of information from this forum and wanted to contribute my current experience. I got my 2001 996 as a roller and this being my first Porsche, I never experienced what normal brake pedal should feel like. Constant pressure to the brake pedal would result in a slow drift of the pedal to the floor. Seemed pretty obvious m/c failure. I replaced said m/c and bled the system with a quart of Dot 4. Did not have the tools to activate the abs but figured I would at most get a spongy pedal. As you can guess, problem not solved. I considered the possibility of installing a defective m/c so I swapped the original back in. This time, the pedal would hold better if I pressed it quickly like in a panic mode, but again slowly drift down with constant pressure. I could tell the problem was in the rear brake circuit as my front brakes would begin squeal in city traffic. Called around for advice, searched on the web and saw some mention on flushing out the brake hydraulics with denatured alcohol, rebuilding all the calipers and bleeding the brakes with the abs activated. After rebuilding the calipers, I finally swapped out the ABS with one I got on eBay and problem solved. Didn't need to activate ABS to bleed. Interesting that I never got a ABS code. I found issues surrounding the ABS in earlier Porsche's but did not come across one in a 996.

 

Good to know. Thanks for sharing!

 

That seems a little strange but good to know the controller doesn't always pop a code. FYI, I've never had to activate the ABS to bleed my brakes and have never had any issues.

How did you like rebuilding the calipers? Those pistons shoot out with some force don't they?

 

That is exactly the sound! Calipers were easy to build.

 

I was told the ABS pump (doubling as the PSM precharge pump on cars that have this option) was specifically coded to the car and a spare off eBay (or anywhere) would not work without an expensive coding operation by the dealer.

Glad to hear this isn't the case as it gives my PSM failure issue some hope once again.

 

I made sure the ABS part number matched exactly. To be sure it was clean, I flushed the eBay unit with about a cup of denatured alcohol, then flushed with Dot 4.

I really am enjoying a firm pedal now!
jim