Need brake help!
 

My car is in the shop right now getting the fluids changed and the shop called and told me the rear calipers are no good, they are taking air in and need a rebuild, i think he said the piston seals were no good. I called Suncoast and they told me they do not make a rebuild kit for the calipers and if I decide to buy new rear calipers for the 996TT it will take awhile to get because they have to order them from Germany.

I'm running the 997TT 350mm rear disc and a 1/2 inch spacer with the stock calipers in the rear of my 996TT. Does anyone know if the 996 GT3 rear calipers will work with the 997TT 350mm rear disc I'm using on my car?

If anyone has a good set of 996TT rear calipers for sale or knows were I can get a set please let me know, I have a bunch of trackdays coming up and hopefully can get this problem sorted quickly so I don't have to miss them.

Yes, the 997 GT3/turbo rear calipers work perfectly with the 997 TT 350 mm rear discs !

Do you know if the 996 GT3 rear calipers will work perfectly with the 997TT 350mm rear discs?

When searching I read that using the GT3 997 rear caliper can upset the brake balance.

Yes, the 996 GT3 rear calipers + spacers will work with the 997 TT 350mm discs.
I have read about the possible bias problem with the 997 GT3 rear calipers ... all i can say is that i have this setup on my car and i track 10-15 days per year and i never experienced bias problem ... for me it's a perfect solution ! ;)

You can get rebuild kits from GMG. You need to know the sizes of your pistons. The kit consists of one square section o-ring and one dust cover per cylinder. The job is really not very difficult. Here are the steps:

1. Remove wheels. Push brake pedal down, and place a piece of wood between the clutch and accelerator pedals holding brake pedal down. This prevents fluid from running out when you open the brake line.

2. Remove brake line from rear of caliper. You'll want flare wrenches for this. I think it's a 14 mm, but not positive. Put a tray underneath, but if you have more than a drop or two of fluid come out, the brake pedal isn't low enough. Adjust wood stick.

3. Remove two bolts holding caliper to spindle and take caliper to a convenient spot for rebuild.

4. Put caliper in a tray to catch fluid. Use C-clamps or plastic grips to hold 3 of the pistons in place. On fourth cylinder, remove dust seal, then try to pull the piston out. Sometimes it comes out easily. If not, use a little air pressure on the hole where the brake line went in to pop it out. I usually place a piece of rubber between the piston and the facing clamp to prevent dinging if the piston pops out hard.

5. Reach inside the cylinder where the piston came out and remove the square cross-section o-ring. You need some sort of pick for that, but be careful not to scar the cylinder walls. Clean interior of cylinder, then lubricate replacement o-ring with grease made for that purpose and/or some clean brake fluid. Clean cylinder, and I also usually run a little steel wool on it. Re-insert and press into place. Sometimes a plastic carpentry clamp is useful to get the piston all the way in. Install new dust cover.

6. Repeat for remaining pistons.

7. Re-install caliper. Torque bolts to 63 ft-lbs. Release brake pedal and bleed.

Hope that helps.

Jon

Thanks Jon, this is great information!

Does anyone know were I can find out the size of my pistons for my rear calipers?

Are you sure you need the spacer, I thought I read that the 996 GT3 rear caliper will work with the 997TT 350mm rear disc without the spacer.

Does anyone know for sure if the spacer is needed with the 996 GT3 rear calipers?

what's the mileage on your car?

is this failure mileage dependent or other?

what are the symptoms?

thanks

I took the car in to my indy shop to have the fluids changed and a general inspection. I mentioned to them the brake pedal had alot of travel. When they checked the brakes they saw that the seals in the rear calipers were wet and told me they needed a rebuild or to be replaced, if you call Porsche they will tell you they do not make rebuild kits for the calipers and that you have to buy new ones, but if you read what Jon posted GMG might have rebuild kits for our calipers.

I do use the car at the track , so that might have something to do with the seals going. The mileage on the car is about 40km.

I have the GT3 brake upgrade on my car, front and rear, and have been using 997TT rotors, and you don't need spacers with this combo.

My '03 is just over 12k miles, bought it 3 months ago with 9k miles, had flush done before delivery yet I never liked the brake feel. Last week I took it the track and brake pedal went spongy on me, now it continues to be very spongy. I'm doing ss lines and ATE Blue Racing see how it goes.

I've been told by alot of shops that our stock brake line are very good and don't need to be changed even for track days.

I never really liked ATE blue brake fluid, used it in my BMW, it will stain your master cylinder. I would use Motul fluid instead.

It's usually the heat generated by track use that makes the seals go. In daily use, the seals should last a very long time.

I think that you can also get the seals from Stoptech - in fact, I think that is where GMG gets them. As I recall, there is less variability with model year in the size of the pistons in the rear than in the front. I'm out of the country, so I can't check my garage where I have a spare set. You might just try calling them. They might be willing to exchange them for you if they aren't the right size. The only way I know of to find out the piston size you have is to take out a caliper, pop off the dust seal and measure it. If you can let the car sit while you wait for delivery, that's the surest way to get the right size.

The seals are not cheap, but a lot less expensive than new calipers. You really don't need to replace the calipers for this. And if you do, you are going to have the same problem again soon enough.

To Frissen: if you ran stock fluid at the track, you almost certainly boiled it. Better fluid will help that. I prefer Motul also. It's nearly the same price as Ate, and has a higher BP. Landjet prefers Castrol SRF, but it's about 5X the price of Motul.

Jon

Yes. i'm sure ... as the rear disc of the 996 TT is 330 mm is clear that if you want to use the 350 mm disc and the stock 996 TT rear calipers you will need a 10 mm spacer to make them match !
Different story if you want to use the 997 TT/GT3 rear calipers ... they will be a direct bolt on !

Do you mean you are using 350 mm rotors front/rear with the stock 996 TT calipers without using a spacer ?
This is impossible !!!