Brake Problem

[Stefano Buganza]

Hello to all of you from a new member and glad to be part of this community! As a recent owner of a 1999 996 cabrio, I have a problem: since I bought the car one month ago it seemed to me that the range of the brake pedal was too long...and it increased more and more so that I drove the car to the assistance, where they told me that there was no air along the brake line, so they stated problem was the master cylinder. A complete repair kit ( http://pages.ebay.com/link/?nav=item.view&alt=web&id=161759416258&globalID=EBAY-IT ) was ordered and installed but, despite of that, after few kilometers again happened the brake pedal increased his range so that now to stop the car (even going slowly), I have to push the pedal completely to the bottom :-(. Pumping the pedal doesnt work that much: always the pedal goes down!

Any ideas about the origin of the problem? Maybe the brake lines? Or what else?

[wizard]

Buona sera. I once had the same problem on my Boxster. In my case, it was a leak of brake fluid from one of the bleed screws which hadn't been properly tightened. You might want to check that, and whether you are actually losing brake fluid.

Edited August 8, 2015 by wizard

[Stefano Buganza]

Thank you Wizard! Do you mean one of the screws fastening the master cylinder?

 

Ok, now I understood: bleed screws are the ones on the caliper!

[wizard]

Yes, on the calipers. There's a rubber cap over the top of each bleed screw. If you remove the cap, any leak will show up on the inside of the rubber cap. If you're tightening the bleed screws, do so carefully.

 

The problem suggests a brake fluid leak to me. Have you checked the master cylinder level to see if you are in fact losing fluid ?

 

As I'm sure you know, brake fluid is extremely harmful to a car's paintwork.

 

Good luck ! 

Edited August 8, 2015 by wizard

[Stefano Buganza]

Not yet! I collected the car yesterday and problem appeared again this morning. I will check in a couple of hours. Before repair the techician (before repair if the master cylinder) told me about a little leakage, luckily not harmful to paint.

[Loren]

Some of the early model 1999 cars also had problems with a leaky seal at the brake booster. If the seal leaks you get water into the booster and that causes all kinds of abnormal brake behavior.

I would check the TSB and then check the brake booster too.

[Stefano Buganza]

Thank you Loren, this is very interesting, my car was produced july 1999!! Maybe is it possible to perform some particular procedure to diagnose if the problem is really the brake booster?

I have this car since about one month and never rained (and the car always is in a garage), despite of that, maybe there is water in the brake booster?

PS now I remember...one time at a carwasher :-(

[Loren]

http://www.renntech.org/forums/topic/15633-brakes-not-releasing-sticking/?p=79485

[Stefano Buganza]

Some of the early model 1999 cars also had problems with a leaky seal at the brake booster. If the seal leaks you get water into the booster and that causes all kinds of abnormal brake behavior.

I would check the TSB and then check the brake booster too.

Checked the TSB, thank you so much!! Now, I found the brake booster on many internet shop (TRW PSA521)...and ALL these sites state that there is compatibility between the part and my car. So, as the part include also the seal (see photo) have I to buy the new seal set too (000 043 204 66) or not? Edited August 9, 2015 by Stefano Buganza

[wizard]

Hello.

As Loren has rightly pointed out, the brake booster is an issue with your model year. However, a defective booster will normally result in it requiring a lot more strength to push down on the brake pedal and, once depressed, the pedal not returning to its original position (remaining depressed).

Before spending on a new booster, I still think you need to establish whether you have a leak of brake fluid. Mark the level on the fluid reservoir with a pencil, repeatedly apply the brakes and then check the level again.

To check whether the booster is working properly, with the engine switched off pump the brake pedal a few times, then, while holding down the pedal, start the engine. The pedal should ease downwards a little as the engine starts.

If you're having difficulty braking the car now, I would caution against driving it in case of total brake failure !

Edited August 9, 2015 by wizard

[Stefano Buganza]

You are absolutely right, wizard. I will consider changing the booster only as a last chance. Lot of things are to be considered first, like an accurate bleeding and the chance that the repair kit for the master cylinder didn't work well! Also deteriorated brake lines could be an issue.

I tried yesterday to do the check you told: pumping on the pedal with the engine off, I got a pretty stiff pedal, then, turning the engine on, the pedal "crashed down" to the bottom!

And finally, thank for your last advice: car brakes are still working, and the autorepair is only 1 mile away!

[Stefano Buganza]

Last update!! I realized I have a "TC off" button on my car dashboard, and looking at the DIY page of Pelicanparts.com, I have seen that in this case, it is needed a "Porsche system tester 2" to do the bleeding. Is that ok? :-(

If so, I have a problem, since here all Porsche houses are closed (and also exorbitant :-/)

Edited August 9, 2015 by Stefano Buganza

[JFP in PA]

Last update!! I realized I have a "TC off" button on my car dashboard, and looking at the DIY page of Pelicanparts.com, I have seen that in this case, it is needed a "Porsche system tester 2" to do the bleeding. Is that ok? :-(

If so, I have a problem, since here all Porsche houses all closed (and also exorbitant :-/)

 

The Durametric software will also activate the ABS/PSM system during a flush.

[Stefano Buganza]

 

Last update!! I realized I have a "TC off" button on my car dashboard, and looking at the DIY page of Pelicanparts.com, I have seen that in this case, it is needed a "Porsche system tester 2" to do the bleeding. Is that ok? :-(

If so, I have a problem, since here all Porsche houses all closed (and also exorbitant :-/)

 

The Durametric software will also activate the ABS/PSM system during a flush.

 

Thank you very much, nice new that will be useful.

 

Last update is that the leak problem seems to be...at the ABS unit  :censored: !! Under the unit a little amount of oil collected, so, now, I have to found an used but fully functional one, and it is not that easy, especially in Italy and in August  :blush: .

Reference of the unit is 99635575528, Bosch nr 0273004179. I tried to check the price for a new one one at rosepassion.com and I was about to faint  :eek: . Maybe in Germany I will found something on Ebay.

[wizard]

Try abs-world-online.de

 

I believe that there is a used one available for € 369.

[Stefano Buganza]

Try abs-world-online.de

I believe that there is a used one available for € 369.

Thank you Wizard! I immediately bought this one http://m.ebay.it/itm/141615322053 , matching both Porsche and Bosch numbers and seller wrote me it is fully functional. :) maybe the end of the odissey is near!

[Stefano Buganza]

ABS unit is on my way, but I have a doubt since the car is actually in a small car repair shop where I am actually in vacation, without Durametric software-cable and without Motive Power Bleeder.

Do you think it is possible doing by now a "simple" bleeding through brake pedal only and then, when I will get back to Milan in september, do another bleeding also with Durametric?

Last question: maybe doing bleeding through brake pedal only could cause damage to master cylinder or (that is worse!) to ABS unit?

Thank you

Edited August 11, 2015 by Stefano Buganza

[JFP in PA]

ABS unit is on my way, but I have a doubt since the car is actually in a small car repair shop where I am actually in vacation, without Durametric software-cable and without Motive Power Bleeder.

Do you think it is possible doing by now a "simple" bleeding through brake pedal only and then, when I will get back to Milan in september, do another bleeding also with Durametric?

Last question: maybe doing bleeding through brake pedal only could cause damage to master cylinder or (that is worse!) to ABS unit?

Thank you

 

You are not going to be able to properly bleed the system after changing the ABS unit without a Porsche diagnostic tool.  If you do not have access to one, I would suggest not taking the car apart until you do.

[Stefano Buganza]

ABS unit is on my way, but I have a doubt since the car is actually in a small car repair shop where I am actually in vacation, without Durametric software-cable and without Motive Power Bleeder.

Do you think it is possible doing by now a "simple" bleeding through brake pedal only and then, when I will get back to Milan in september, do another bleeding also with Durametric?

Last question: maybe doing bleeding through brake pedal only could cause damage to master cylinder or (that is worse!) to ABS unit?

Thank you

 

You are not going to be able to properly bleed the system after changing the ABS unit without a Porsche diagnostic tool.  If you do not have access to one, I would suggest not taking the car apart until you do.

I thought to collect the car with the new ABS unit (obviously if it will brake!), have it at home until the Porsche repair will open and then carefully drive it to Porsche. But if you tell this is not possible, only chance will be to use a tow truck.

[wizard]

If I understand JFP in PA correctly, a Durametric will do the trick to ensure that the braking system is properly bled, includIng the ABS module.

I would have thought that investing in a Durametric cable would be a more practical solution instead of throwing money away on a tow truck.

I hope that you get it all sorted.

Edited August 12, 2015 by wizard

[Stefano Buganza]

If I understand JFP in PA correctly, a Durametric will do the trick to ensure that the braking system is properly bled, includIng the ABS module.

I would have thought that investing in a Durametric cable would be a more practical solution instead of throwing money away on a tow truck.

I hope that you get it all sorted.

Sure you are right, and I could try to find Durametric here in Europe in order to have it delivered soon. The problem is that JFP in PA wrote that "to properly bleed the system after changing the ABS unit" a PORSCHE diagnostic tool is needed, not a "simple" Durametric one.

[JFP in PA]

Durametric, which is a Porsche specific tool, will correctly activate the ABS/PSM during a hydraulic system flush and bleed.

[Stefano Buganza]

Durametric, which is a Porsche specific tool, will correctly activate the ABS/PSM during a hydraulic system flush and bleed.

:thumbup: all clear! See you later with my brakes definitively fixed!

[Stefano Buganza]

At last ABS unit has been mounted, regular bleeding done and pedal was very stiff! Durametric arrived but when I connected it, I had the (bad) surprise to see that communication with a lot of unit was not possible.

Any suggestion?

 

 

 

 

[wizard]

Is the Durametric cable new or secondhand ?

I ask this because on the entry level kit I believe that there's a limit of 3 vehicles, based on VIN.

Edited August 19, 2015 by wizard