GRUWEZ

Guys,

I am about to tackle -- once again -- the brakes on my 1997 993 Turbo. I did them last year because the inside of the brake rotors were severely rusted. At that time new rotors and pads were installed. That was something I did myself in my garage. I also had the brake fluid flushed and the system bled at the dealership. Now, merely one year later, the inside of the rotors are once again severely rusted. I tried driving the car and braking heavily, but that does not help. It seems to me as if the inside pads just do not contact rotors.

Any idea what could be wrong?

Here are some photos of the symptoms. Not nice, huh?
Thanks for letting me know what could cause this.
Regards,
Rik Gruwez
Bruges, Belgium

Barney1

Seems like the caliper is only applying pressure to the outside pad...are they worn uneven??

jimq

Stuck pistons in the caliper maybe

Barney1

Yup....you have bad calipers.. the inside pistons must be frozen...

GRUWEZ

Don't know. Have not done anything yet but put the car on the hoist to check out the brake rotors.

OK. Can I get a caliper rebuild kit from Porsche?

Barney1

I dont think they make a rebuild kit.... Do a search and you will find some good used calipers.

Barney1

Here you go...
http://cgi.ebay.com/Porsche-993-Turb...3286.m63.l1177

Felix

Are the stainless steel plates inside the calipers that the edges of the pads rest on lifting and preventing the pads from moving properly? Corrosion develops underneath the plates and causes them to lift. Did you have any trouble installing the new pads into the calipers?

IamSMC

GRUWEZ:

PM Bill Verburg regarding your brakes, he knows alot about Porsche brakes.


Also, you want to contact this company to see if they have what you need:
http://www.vehiclecraft.com/index.html

GRUWEZ

Actually yes. I even called the dealership to ask them why I had such trouble installing the new pads. The advised me to trim a bit off the pad edges to make them fit.

Regards,
Rik

Felix

I think that could be your problem - corrosion under the plates causing the pads to jam.

911/Q45

Caliper pistons can exert so much pressure that it is unlikely that the pads wouldn't make contact due to this, much more likely would be a failure to release resulting in overly worn pads. Lack of pad contact is almost surely due to corroded pistons and bores because of old brake fluid and can only be fixed by caliper replacement.

IamSMC

I see "Caliper Piston Seal Kits" listed here:
http://www.pelicanparts.com/catalog/...BRKhyd_pg3.htm

GRUWEZ

Thanks to all for the great feedback! I suppose it is time to disassemble everything and check out what is wrong. Sounds like a nice winter project.

GRUWEZ

I removed one caliper today to do some more investigation. The pistons and bores turn out to be OK. Check the pictures below. I do not see any corrosion or other damage that could lead to a binding piston.

However... it was impossible to pull out the pistons by hand. They are a very tight fit in the bore. As it turns out, the tight fit is caused by the bore seal. After I pulled out the bore seal, the pistons can be freely moved by hand in their bores. Now I must say it is quite cold in my garage/workshop, probably around freezing, which makes the rubber seal probably pretty hard.

So far I still have not discovered what could cause the inner pads not to touch the brake rotors. I spoke to Gert at Carnewal and he did not have a clue either.

Does anyone have an idea where to look further?

Thanks,
Rik