Brakes failed...on 1999 996

[Keith Z in DC]

I have major brake issues...got in my 1999 this morning to go to work and the brakes did not respond in the normal fashion. The brake pedal when pressed, only activates the brakes for the first 3/4 inch of travel. The pedal then gets hard as a rock and an increase in pressure does not increase the braking ability of the car. If you release the pressure and apply the brakes again, it still only responds for the first 3/4 inch of travel. I checked the fluid level and the level is fine, plenty of pad left, car does not pull when brakes are applied while driving and...the hand brake obviously still works. Any ideas? Any recommendations?

Thanks,
Keith

[herman maire]

I have no idea what it is but it could be a faulty ABS unit, computer, master cylinder ect... It could be something really simple too like something jamming the break pedal arm.
good luck

[Keith Z in DC]

Thank you. I did check to see if there was anything blocking the pedal travel and it does not appear to be the case. I was thinking maybe a seal failed inside the master cylinder...just not sure how to trouble shoot that on my own.

I have attached a photo of the car...not for diagnosing the brake problem, just because I have not posted any photos of the car.

Thanks again,

Keith

[herman maire]

Keith
Car looks good. You should post your problem over on rennlist.com , they have a pretty active 996 forum over there and you should get a better idea of what the problem is.

[450knotOffice]

Very nice silver 996, Keith in DC!! As to your problem, it sounds to me like you've checked all of the items I would look at. It may be time for a real pro to diagnose/fix your problem.

[Keith Z in DC]

Thanks! I'd be interested in seeing photos of your 3.0 CSi sometime. I will join Rennlist in the morning and post my problem.

Thanks!
Keith

[Keith Z in DC]

Thanks! I guess as long as the accelerator pedal still works it is fine! The downside is I just had it in the shop a week ago for the 90K service. I guess it is time to head back...

Keith

[Aerkuld]

Does the brake feel the same way as you describe without the engine running? If there isn't anything physically limiting the brake travel then I would have to say it sounds remarkably like a brake booster failure. I would expect you to be able to feel an increase in braking force if you pushed the pedal harder though. Still, it might be something else worth looking into.

Good luck and please keep us posted.

[TCallas]

I agree with the previous post, this appears to be an obvious brake booster failure or loss of vacuum to the brake booster assembly. I would remove the vacuum hose to the booster and check for a good vacuum supply. While the vacuum hose is removed, I would use a long plastic ty-strap and dip it into the booster to check for any water or brake fluid existing inside of the booster reservoir. I am curious if the vacuum check valve is OK? I do not have a schematic in front of me but that would be the next area to inspect. One last note, I have seen this before on a race car when someone installed the incorrect brake fluid reservoir cap. The cap was not a vent style and did not let the reservoir breathe. I am pretty sure that this is not your problem, just an FYI for all.

[Keith Z in DC]

I didn't see your post until this morning but I have included the post that I just sent to Rennlist. I am wondering now if I have water in the booster that is freezing in the cold temps. If so, can I drain it and save the booster? Or has the damage been done? I had vacuum at the booster but the temps had warmed a great deal. I will keep trouble shooting.

Thanks!

Here is the post:

Thank you everyone for the input...but the plot thickens. So, I was short on time this weekend and only got to spend a few minutes with the car. I read and cleared the codes, inspected the booster and lines/hoses that everyone mentioned. Didn't see anything totally out of the norm so I fired it up and the the check engine light did not register the codes once cleared. I pressed the brake pedal and the brakes were back to normal. One thing to note, the temperatures were in the 40s. Could the warm temps be masking the vacuum leak? I assume that the hoses become more flexible when warm and could that possibly be enough to prevent the vacuum leak from occurring?

I must add I spent 4 years in Stuttgart when I was younger and I do recall some very cold days...do I now own a warm weather only car?

My best guess is that the booster is still functioning and I have a vacuum leak. Thoughts?

Thanks,
Keith

[tshih]

Keith,

When you said it had the 90k miles service does that mean the brake fluid was changed and air correctly bled from the entire brake system lines (except for the ABS circuit which is not part of the regularly serviced part of the brake fluid lines)? Also are the brake pads stock or track modified use (which needs warming up for proper response). There are different pads out there for DE or track use which squeal a lot when cold (and used on the streets) and don't work well cold. On cars that have never had their brake fluid changed every 2 years or after several track events rust and other problems often develop in the lines leading to strange responses like what you describe. It was very cold last week for 2 days before the spring thaw today.

[Keith Z in DC]

The shop owner is a great guy and he is very concerned about the situation...even though I put a couple of hundred miles on it since it was in his shop. It has not seen any track time (yet), normal pads... He pulled the shop records and the mechanic made note of how clean the fluid was and that he changed it anyway. He also noted that I will need rotors when I have the brakes done in the future. I have confidence in the shop, they build some very nice race cars (GT3 Cup car and a few others)... He also had what I think was a 2007 GT3 RS on the lift. I'm sure they bled the system properly. I will ask when we talk again. I will also ask if he minds if I share the name of his shop. He is located on Long Island (NY).

Thanks for the insight!

Keith

[tshih]

How hard or expensive is it to change the vacuum booster in a 996? I suppose the hose should first be checked as suggested before you spend the bigger bucks for other components.

[wsp8]

Keith Z in DC ... what was the end result of this situation? I've just bled mine (& clutch slave cylinder) and the pedal is as hard as a rock though I haven;t fired it up yet! Thought it was a good thing, but maybe not.

BTW, who did you use? GT Performance? I'm over in Annapolis and always looking for a good mechanic. Thanks!

[Keith Z in DC]

You will need to start your car to have the vacuum assist work. As for mine, the car is in the shop getting a new motor installed. They are going to trouble shoot the brakes. I am almost certain that water is getting into the booster as it only happens in zub-zero temps.

As for the shop, I relocated to NY since I joined this site. I am using Rudtner's Racing Group. They are great...I'd say they are even worth the trip from MD! I have a great shop in Richmond if you are interested.

Thanks,
Keith

[wsp8]

I think you're right. Joel Reiser, tech. ed. of the 996 PCA site, has mentioned this problem several times. The drains for the cowl clog, then water just runs right in apparently.

Good luck!