Hello,

I have a question regarding my Row 5 speed '77 Porsche 928 (n°533). It was first registered 11/11/1977. This week I took out my brake master cylinder since it needs replacement. In the workshop manual here's talk of brake pressure regulators. However they're not on my car. If i inspect the manual further I tend to come to the conclusion that brake pressure regulators were used from december 7th 1977. Is this conclusion correct? If I replace my master cylinder should I install them or do I have to make sure that I have a pre december 1977 cylinder? I also discovered a "white thing" that connects brake lines but I can't seem to find it in the manual. Here's a pic of it. Can U help me out with what this is.




Greetz from Belgium

 

We could all use bigger pictures.

The brake pressure regulators, if you have them, will by cylinders mounted to the fender wall somewhat before the master cylinder.

I wasn't aware of a brake change on very early cars. Did they use masters with two different-sized pistons to get lower pressure to the rear? 944s have that.

 

The picture shows the original check valve (possibly, or could be a replacement). A new one will look blue and black.

Looking at PET, I don't see any fundametal changes to the brake MC. There are no VIN splits from early to late '78. P/N 928 355 011 04 should work for you.

I received your email, and thank you for the kind words. Figured it as easy to respond to you here.

 

Thanks for helping out. Is there a reason why there's no brake pressure regulators on my car? Anyway it braked fine before so it will probably do without. Now there's another thing thats confusing since there's a difference in the brake fluid mentioned in the workshop manual (dot 4) and the brake fluid in the user manual (dot 3). I'd ilke to be sure about the fluid 2 use. So if anyone can give a definite answer...
@jadz 928.. I hope U didn't get the mail 3 times since I had some problems sending it :-))

 

DoT 4 is a higher spec than DoT 3 but is backwardly compatible. DoT 5.1 is also backwardly compatible with 3 or 4.

DO NOT BE TEMPTED TO USE DoT 5.0 it is not compatible with anything in a 928 brake or clutch system.

 

Let me fix this:

They can be hidden amongst wiring, tubes and dirt. They're maybe 2 inches tall and 1 inch wide. Lots of cars have them mounted to the master cylinder itself if that's where you're looking.

 

The very early cars had diagonally split brakes, so no front/rear pressure regulators. One master cylinder piston operated the right front and left rear brakes, the other piston operated left front and right rear.

You shouldn't have regulators.

 

Ok thanx folks. Indeed there's split brakes so question answered. :-))
For those who'd like to see some pictures and perhaps learn some Dutch (close to German but not that close) here's a link to my blog.
http://www.bloggen.be/sharknose/