Failed ABS Unit
 

So recently at the track I had an off because of a rear tire failure. Before my next event, I started getting ABS/PSM failure lights driving around town shortly after start up then immediately at start up. At the my last event, I found ABS was truly OFF when these lights were on and I was locking up the rear tires fairly easily. Fluid level when I checked was near top marks on the reservoir, however randomly at low speeds the pedal feel would go soft on the way home from that event.

I figured the wheel speed sensors were suspect as they looked original and with my luck they've become victim to poor design and seized themselves into the carriers. Dropped car off at the shop to have wheel bearings, hubs, and the sensors replaced, with fingers crossed that was my issue. Until the phone call.....

Looks like the ABS unit in my car has been replaced before. The prior care taker for some reason saw it fit to jump the low fluid level sensor as well. Apparently, the ABS unit that is in the car is known to have an issue with leaking out of this center hole that does not exist in the superseded units. There is considerable fluid leaking out of this center plug on the unit.

Options are :
New unit from Porsche with warranty ~$5500
Used unit from parts supplier with warranty (will call around tomorrow)
Used unit from parts supplier without warranty
Used unit from forums etc (I can install any 6 fitting 996 w/psm unit you source to your current module)

Thoughts? Votes? The car is about 50/50 track and street use.
https://cimg7.ibsrv.net/gimg/rennlis...f88b01269d.jpg
https://cimg9.ibsrv.net/gimg/rennlis...5936fe8c26.jpg

What were the codes in the ABS unit?

If that fluid leak from the black cap is indeed causing the problem (which I can't believe - I think it's a second problem) then I'd find a used one and swap the module. If that leak is a second problem, then it depends on the codes that are in the ABS. There may be a problem with the module in addition to the leak.

Jumping the fluid level switch is kinda stupid, though I understand why - it randomly activates unless the fluid is at the very top. Then you get a scary warning message about brake failure which is very distracting to say the least, it popped up on my car on the Uphill at Lime Rock.

Unknown of any codes stored in the ecu at this moment.

Seems reasonable to just swap the entire unit with a good used one. Anyone have recommendations? Found one on eBay and plan to call around some dismantlers tomorrow. Porsche wants 5500....which is just insane to me. This can't be just turbo/c4 specific unit?

Mechanic thought that perhaps previous owner ran fluid a little low so it didn't leak on track, but seems like a good thing to have operating correctly.

The name escapes me at the moment, but someone posted about a company that will rebuild it fast, economically.

Module masters has some ability with this unit: https://modulemaster.com/. Finding the correct ABS unit with first generation PSM has been quite difficult. If the rebuild option works out for you please let us know

Yes I agree that 5500 is a bit rich.

What you need to do is to find the Bosch part number of the module. Use a mirror to read the Bosch part# as it's on the bottom of the module. Then search for ABS units that look similar: six fittings and the pressure sensor on the back. When you find one make sure that the Bosch part# of the module is the same.
The Porsche part# on the casting - the part# that you can see next to the pipes - is only the part# of the aluminum casting. Don't use it as a complete guide. The Bosch part# on the module is what you want to find.

The Bosch part# is a 10-digit number formatted something like 0 123 456 789 .

Thanks, they just so happened to have one on the shelf for 500 bucks. Ordered. Will probably send out my current for rebuild just in case. Seems to be pretty common on heavily tracked 996s? Porsche recommends their classic brake fluid for 996 and older chassis which is a little thicker than the new fluid, SRF has a similar viscosity so will switch to that.

Well, that turned out well - can't complain about 10 cents on the dollar for a Porsche part.

:)

That's it.

FYI, Module Master will not / does not do any work on the hydraulic portion of the abs unit. Just the control modules/solenoids.

Not sure what's going on right now but this is eerily common. 2 threads about this recently and my car has had issues now...

My car locked up at all 4 wheels recently and I couldn't get it to unlock for 30 mins. Brake pedal was rock solid at the top the range and all four corners had smoke coming from them (brakes). Car fried both fuses that deal with the ABS/PSM. Ended up disconnecting the abs unit and they finally unlocked....car is in the shop and I was told a relay in the ABS unit was stuck on which caused the fuses to fry (Mechanic stated the system isn't made to stay on, only short bursts which is why the fuses fried). ABS unit was sent to Module masters due to the bad relay.

Prior to this happening, the car was being driven in the wet. PSM had kicked in 3-4 times....then ABS and PSM lights kicked on. I looked down (and took my foot off the gas) to see what was going on and the car came to screeching halt....glad I a wasn't rear-ended by the 991 that was following me and glad I was going straight when it happened.

sounds like controller can be fixed which is good for you. The hydraulic valves doesn't seem to have any fix for it when it goes.

Is this really a common issue with cars that see track time? Makes me nervous.

I put 20k miles of track driving on mine and never had an issue and same goes for many others. Sometimes parts just break.