Sean and I just did this job on the GTS. I replaced ALL gaskets and O-rings as they were TOAST for sure! Not sure if the additional gaskets were required on later model years, but we did add some permatex gasket sealer around the two waterbridge to head surfaces there. NO leaks after a month.
(knock on wood)

Used Dwayne's prodcedure and it was pretty straight forward.
http://www.dwaynesgarage.norcal928.o...aterbridge.htm
The only problem we ran into was trying to get the driver side (aft) mounting bolt to catch and go in straight. We ended up slightly buggering the threads about 1/2 way into the hole. Cut off a small portion of the end of the bolt and tightened. We'll tap and clean it up when we pull the intake off for a refresh and have a straight shot at it.

But wouldn't copper, steel and aluminium in a damp environment be a recipe for corrosion. Maybe Optimoly TA (aluminium paste) would be better for this application?

Good point about the Optimoly, although I never experienced problems with copper grease.

I just got out of the garage. The seal for the thermostate only existed of the metal ring; the vulcanised rubber on it was half gone and the other half I could peel of. So I'll replace that one too. Another problem is the U-groove is partly damaged for both seals to the cylinder banks. U filled them up with 2K-special filler and it's baking in the oven right now. Tomorrow, I'll sand it flat and cut gaskets from sealing paper. With sealant, I'll mount everything and keep my fingers crossed it will be leakage free...

Same here. I am hoping mine does not leak for a few years also.

P.S: Bart, I sent you a PM about your Megasquirt install. HK

Bart-Jan,
What size were the allen bolts you replaced? Getting ready to replace them during my intake R&R.
Thanks,

I just did this job on my 89 s4 as part of an intake refresh. I snapped the long bolt, which was a bit of a gulp moment for me. I called my mechanic who is also a good friend and on sunday afternoon he came around with his gas set to help free up the stub, which then broke off flush with the block...

He then drilled it out, and did it so well that we could just chase the thread afterwards and did not need to helicoil it.

The bolt was an m8x70.

I was also puzzled by the additional paper gaskets under the two arms for the water bridge as they were not in the manual and did not come with the gasket kit. In the end, I used gasket goo as well to be on the safe side (and glad I did after reading the bulletin above). No leaks so far but its only been 4 days.

Jason, sounds like you have one of the afflicted '89 engines too then? Interesting that the gaskets were already fitted on your car - it implies that the water bridge has already come off previously for work, most likely by a Porsche dealer, who had access to the service bulletins.

My '89 was all factory-original and didn't have them - seems it was an issue that emerged after production hence the release of the technical service bulletin about using those gaskets on the few early '89 engines.

I just discovered that my '90 S4 (#392) also has the extra gaskets and I was also worried about that long bolt. It actually broke loose fairly easily, but started binding on the way out and pulled out just a little thread. Cleaned up the threads on both the bolt and block and I think it'll be OK. It'll go back in with anti-seize, though. :)

I used Permatex 98H on both sides of the gaskets, too.