Hey gang,

My 89s4 is losing fluid from MC. How hard is it to rebuild it? I see Porsche MC for $500 vs Porsche rebuild kit for $90. Is this a DIY job?

 

I believe you will find that Porsche (and everyone else) does not have any of the late master cylinders, at this time.
I installed my very last new one that I had in inventory, two weeks ago.
Rebuilding, which is fairly easy, if the bore of the master cylinder isn't damaged, may be your only option.
We've got a local professional rebuilder who put new sleeves into the bores, but getting pieces back from him is difficult...he's extremely busy.

 

I've had 4 rebuilt very successfully.
The last one took a lot of sweat to get it apart. The shop sent it back to me, said they couldn't get the piston out.
I made a very simple bar that clamped to the external piston shaft, with 2 bolts through it that pushed on the mounting flange and it came apart quite easily.
Then they rebuilt it.

 

White Post Restorations has been mentioned in the past.

 

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Are the cups/seals available for these?

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For those playing along, this is a reminder that religious attention to keeping clean dry fluid in the system goes a long way towards keeping master cylinders, calipers and plumbing happy. A sage expert shared decades ago that hydraulic system maintained with clean dry fluid will last forever. I'm not that expert but learn from those who are. If your brake (and clutch and PSD) fluid are more than 2 years in the car, it's time for a flush with new. If the fluid in the reservoir is anything but clear to maybe a pale yellow, change it. The ONLY thing that discolors fluid is corrosion.

 

Where is this kit available?

 

Pelican Parts

 

Pelican shows MC rebuilt Kit as 928 355 913 02 (was 928 355 913 00) which is only used on 928 MC 78 to 83.
I am not aware of a rebuild kit at this time for the later MCs.

Master cylinder 928 355 011 25 - I have two in stock (Last Two)

 

What is so special about the 928 that its master cylinder fits this car and only this car? I find it hard to believe that no other unit can be adapted. Last I heard the master cylinders were over $500 and the reservoirs over $200- to me this is outrageous. Sounds like one of those items we need someone to step up to the plate and come up with something that is easily adaptable.

 

With some creative plumbing, I wonder if you could adapt a late model 944 master cylinder:


This is from my '91 944 S2

I just sort of held things up as close as I could, and I don't know how different the MC is on the manual 928s (mine is an auto, which is where the one in my hand came from), but the bolt spacing to the booster looks like it's the same. I'm sure there are other specs to the part that play a role but I figured I'd throw this out and had the easy opportunity to compare.

From Paragon, there are MCs available for ~$250.

Cheers

 

Good idea and it may be possible to use it. However they are in just as short a supply as the 928 MC. Checking all the wholesalers there are only 2 available. Price $275 and Porsche NLA.
Also the 951 MC is now only available via Porsche for circa $600.

 

Porsche appears to be going back to the original vendors and having pieces remade....like the fuel pressure regulators and dampers.
However, it appears that at the same time they are negotiating for making the parts, it appears that they are also negotiating an "exclusive" for those same parts.
And with the current "legal system", is $600 outrageous for a master cylinder, given the product liability exposure?

I think we are going to have to get used to it....

 

Try these guys- they are the guys that supplied the seals for the psd & clutch slave cylinders - they can make anything- call & send a sample- might not be able to do master cylinder seals, but a phone call should tell., worth a try


https://projects.iq.harvard.edu/file...g_handbook.pdf

 

This. They rebuilt my brake master cylinder this summer. Total cost was about $250.

Rich