Mike Murphy

DBJoe996

You have first posted of this problem on July 6th and asked for help from an internet forum. Many have weighed in and offered advice. You still have the problem. Perhaps you should consider taking it to a professional brake specialist for evaluation. Horror of horror I know, but even a Porsche dealer has some very experienced technicians. Brakes and brake systems are something you really need to have work perfectly.

Porschetech3

If you are determined to repair this issue your self, I suggest you get a quality Digital pressure gauge with a range of 3000 psi and an accuracy of 1 psi and install it at your caliper for diagnosis. You can get fittings to install at the bleeder valve or at the flex hose.

De Jeeper

I think i would have just bit the bullet and got a new booster and 996 master or maybe the 997 master. I have seen threads on the upgrade? U have already replaced the most of the system not that many more things that can be wrong.

mayday1

mayday1

A new vacuum booster from TRW arrived this weekend, and I measured the push rod, and it is recessed 1.5mm more than the old booster., that gives the need clearance to avoid constantly pushing the
master cylinder piston. After putting it in, the brake drag problem seems to be gone. I drove around a couple of hours and the front wheels were hot (50-55C) and the rotors were about 60C, so I think the problem is fixed.

Unfortunately the one of the hard brakelines from the ABS to the fender has a slight weep. I didn´t tighten the brake lines to the ABS too much since I was worried about stripping the aluminium block, I tightened the said
line by about 1/4 turn, we´ll see if that fixes the weeping.

I need to bleed the brakes again since they now feel a little spongy, may be I didn´t bleed properly or that weep was causing the spongy brakes.

At least there is light in the end of the tunnel! Thanks for all those suggesting the replacement of the booster, I should have listened to you guys and wouldn´t have needlessly replaced so much
stuff. Live and learn.

Kris Murphy

If your car is a manual, you will likely want to bleed the clutch slave too as part of your bleeding process. You've had the system open a bunch, so best to bleed it from all possible areas. There is a good writeup on RennTech and Pelican.

De Jeeper

Meh its probably not a bad thing that u rehabed the rest of the system.

Ahsai

Glad you've found and fixed your problem. If the abs hydraulic lines have been opened, I've read that you'll need PIWIS to cycle the abs valves while bleeding. I think Durametric can do that too but not sure.

mayday1

I hear you, even though I didn´t notice anything funny with the clutch, the clutch slave cylinder was last replaced 14K miles ago in 2012, and the previous ownerś receipt says the fluid was replaced with Motul. It is now six years later so I should do a
fluid change this summer since I don´t want to mix Pentosin with the old Motul. Back in January I changed out the LWFW with the OEM DMF, and can vaguely remember that removing the clutch slave cylinder from the tranny was a major pain. I hope bleeding it doesn´t require dropping the tranny again!

cds72911

You can bleed the slave from underneath without removing it. It has a bleed nipple like a brake caliper. It's tight, but you can do it.

Kris Murphy

Removing the right rear wheel makes it much easier. Still sucks, but not nearly as much as replacing it.

rolex11

deleted...

mayday1

It turned out to be pretty easy to bleed the clutch hydraulics, but I cheated by using a pressure bleeder.

The car is working fine now, ready for a workout at this weekend's autox.

BTW. I noticed some similarity between the 996.1 ABS unit and my miata's ABS unit.



miata


996.1