sgt1372

So, I initially decided to replace the pads, rotors and brake lines on my 2000 C4 Cab because the brake pedal was feeling "soft" to me. The other reason to change the rotors and pads was that they were very clearly worn.

Had/have to press the pedal about 1/3 way down before it engages and it never felt "firm." Sorry I can't be more descriptive but anyone who has experienced "soft brakes" should have an idea what I am talking about. FWIW, the brakes on my BMW, MB, MR2 and F250 are all "firm" (not soft).

Only the brake pedal on the 996 feels soft to me.

Anyway, last week my Indy installed the Akebono bads, Brembo rotors and Stop Tech stainless steel brake lines and, of course, did a brake flush and bleed in my 996 and the pedal still felt "soft" -- no real change.

WTF?

So, I did some reading on the NET, which can be a dangerous thing to do, and it was suggested that the master brake cylinder could be the culprit. The Indy only wanted a little more $ to replace the master brake cylinder w/an OEM part (adding the necessary fluid and bleeding the system again). So, I told him to go ahead and do it.

My Indy did the work yesterday BUT still no change!!!

So, I'm at a loss. Basically, everything has been changed in the brake system and it still feels soft -- too soft for my taste. I'm tempted to take it to my Dealer to see if they can diagnose the problem (Is a full system pressure test possible to check for leaks?) but before I have to resort to that, does anyone have any other ideas for the possible cause of this "problem?"

FWIW, my Indy talked sh*t about the Akebono pads that I asked him (but that he really didn't want) to install.

I don't think the Akebonos are the problem because they stop my BMW 335i (which has a very firm brake pedal feel) fine. He also had to remove the front brake pad shims that were on the pads that he replaced w/the Akebonos because they didn't fit on the Akebonos. That bothered him a lot too.

Wrote all kinds of CYA sh*t on the work order about it. I further told him NOT to reattach the rear brake pad dampers, which he also didn't like and wrote about up the work order as well.

The shims and dampers are only necessary for anti-noise/squeal purposes and the Akebonos have not made any noise or squealed in the 200+ miles that I've driven it since they were installed.

The new mgr at my Indy is a kinda of "by the book" and "color inside the lines" kind of guy who I don't really like and am planning to find another Indy shop for work w/in the future on my 3 German cars, including the 911. Liked the previous mgr much better, who also seemed much more knowledgeable than the current one, but he's gone now.

In any event, if anyone has any ideas about any OTHER possible causes for the soft brake pedal feel in my 996, I'm all ears!

Mike Murphy

I don’t have any amazing wisdom bits for you. I could never really understand why some cars have a stiff brake pedal, and a different identical car does not.

Most of the time, it’s pads and air in the system.

The only thing you haven’t tried yet is the vacuum booster, correct? If that’s the case, I’d check that, along with the vacuum your engine is generating.

sgt1372

Thanks for the response.

I did a vacuum test w/a manometer attached to the oil filter cap to check for an AOS leak and it came back at 4.6-4.7 inH2O, which I understand is spot on. Not sure how to check the engine vacuum otherwise. May ask my Porsche dealer to check the vacuum booster and see if they can find any other possible reason for the "problem."

I'm stubbornly refusing to believe the problem is the pads because they are brand new and the Akebonos work fine in my BMW. Also not sure how the pads would affect the brake pedal feel especially since the pedal feels essentially the same as it did before the installation of the new pads/rotors when the old pads/rotors were severely worn.

Going to let it go for now. The car stops and that's really all that matters. The only problem would be in a panic stop situation, which I experimented w/a couple of times, and there is a definite delay in stop time/distance that could cause a problem in an emergency. Hopefully that won't happen before I take it into the dealer for a further inspection.

SoCal911t

I swapped out my Textar pads with Akebono a few weeks ago and the pedal feel didn't change. I also used the same shims/dampers and they work just fine with the Akebono pads.
As far as your soft pedal, I wouldn't replace anything else until I was SURE the brakes have been bled properly.

sgt1372

The brake fluid has been bled at least 2 times by my Indy in the past week; once when the new pads/rotors & new brake fluid were installed and again when the new master brake cylinder was installed.

Brake pedal felt the same after both events. Of course, I don't know if they were "properly" bled but w/the equipment they have, I can't image that they f*ck it up. This is why I'm thinking to taking it to the dealer as a "last resort." If they can't do anything w/it, probably no one can.

Indy said the shims on the old pads (don't know what brand) didn't fit the front Akebono EUR 776 pads that I bought and told him specifically not to install the dampers on the rear Akebono 738 pads. Just didn't think I needed the anti-noise/squeal shims/dampers and, based on the driving I've done so far, I don't.

Update: Just made an appt w/my dealer to take a look at it next week. Will report back later w/the results (if any).

SoCal911t

My pads are the 776's and the shims were from AutohausAZ just listed as "OE Supplier" and "O.E.M.".

Mike Murphy

Cool. I’m curious what they find.

sgt1372

Me, too!

Took the car up to Sacramento to look for a 2001 Turbo that was supposedly for sale there but never found it. However, the feel of the brakes actually felt worse; brake pedal drops about 1/2 before it fully engages and is very slow to stop. Very worrisome.

Also "discovered" another problem that I probably caused that I'll have them look at as well The fuel gauge is now stuck on FULL probably because I've been overfilling (until there was/is some runoff) so that I could more accurately measure gas mileage which seemed erratic to me. Just going to ask if they can fix it w/o doing the whole calibration routine. If not, I'm just going to ignore it and continue to guess as the fuel level base on the miles driven and my manual calculation of fuel mileage.

here also seems to be a problem w/excessive back pressure in the tank which forces the fuel nozzle at gas stations to click shut way too fast so that I have to hold the handle in order to fill the tank. Don't know if this is a related problem or not. Didn't start happening until I started overfilling the tank. So, it probably is related. Will mention this to the dealer as well.

joseph mitro

it seems you've replaced all the issues that needed to be replaced other than the brake lines.
I suspect your culprit is either 1) your pads are softer than you like or 2) it's just the way this car is.
My Boxster's brakes felt firm at first with brand new Hawk HT10 pads but then after bedding in, felt softer than I liked. I just got used to it

sgt1372

Guess we'll find out shortly but I still don't think it's the pads because I have the same pads in my 335i which stops on a dime and I don't see how pads would affect brake pedal travel and feel.

Just hope the dealer can figure it out and fix whatever the problem is, otherwise I may try to sell it because I don't feel "safe" in my 996 the way the brakes feel.

Mike Mullins

Overfilling can get in tank vent lines and other tank plumbing, You can gain accurate measurements letting it shut off on first or second auto release on Dover handle) One thing you can do to help with shutoff is not put nozzle fully into receptacle. Other thing to try is turning nozzle 180 degree from normal, Shut off works the same.

Good luck.

sgt1372

Yeah, I think I really f*cked things up in the fuel tank.

The car's still at the shop (24 hrs now) and they're still trying to figure out what's wrong/how to fix the tank as well as the brakes. Oh well . . .

DBJoe996

dporto

About a year ago, I had a similar problem. It turned out to be the ABS Module. There’s a diaphragm that goes bad & leaks fluid out the bottom of the module. You should be able to notice if you’re losing fluid just by checking the reservoir. The problem is you won’t see it on the ground, as it’s in the bottom of your frunk. You’ve got to pull the drivers side liner out and shine a light down there - if it’s leaking you’ll see it. The up-shot is that you can get the modules used, and they’re pretty cheap (less than $100) - the job itself isn’t overly difficult either - 4 brake lines, then bleed brakes. I think I did it in about 1.5 hrs... good luck

sgt1372

Thanks for the tip.

Just spoke w/the Service Mgr (because the Service Advisor still didn't return my calls) and they still haven't figured out what's up w/the car. Gave him an overview of the problems (some of which the Svc Advisor didn't list on the woksheet) and mentioned the tips suggested here.

He said he'd get back to me w/a further update tomorrow. Hopefully, he'll have something productive to tell me.