I have a question about my 1990 964 c4, I wonder if members could be so kind as to give me advice.
The previous owner upgraded the calipers on my recently purchased 964 c4 to the larger 928 S4 “big blacks”. It looks like they have the original c4 brake master cylinder, it’s labelled as an ATE product 964.355.025.52. The brakes have worked really well until a Porsche Club Autocross I participated in over the weekend... the brakes lost their hold…
If I apply heavy pressure to the pedals they will hold firm but if I apply light to medium pressure they will sink slowly to the floor. Someone has suggested that this is an internal leak in the master cylinder.
My question is what part (number) should I replace this broken m.c. with? It’s funny, according to the PET document the factory part for the 964 c4/Turbo is listed as a different part number than the one in my car. It’s listed in PET as part 964.355.903.00??
So, would you suggest I stick with the original factory part number 964.355.903.00 or upgrade to a 993 m.c.(do other parts need to be upgraded if I do the 993 m.c. upgrade at the same time?)?
Any advice or tips from you would be greatly appreciated.
