mstorrente

Hi everyone.

Iīm writting you from Spain, so please excuse my gramatical mistakes.

I own a 1979 Porsche 928 auto, wich brake booster I need to change. Itīs a 9" diameter but that piece is too dificult to find, so I need to know if I can change it for a 10" one. Does anybody know?

Thank you very much...

John Speake

Try Roger Tyson at 92sRus, he's in the USA but can supply you with all parts at a VERY good price.
http://s287999742.e-shop.info/

email him...

ROG100

Thanks John - the 9" booster is pretty much NLA and if you do find a new one very expensive at about $3k last time I looked. A used one from Mark at 928 International would be an option.
Using the 10" looks possible parts wise and it uses the same master cylinder. The linkage to the pedal looks slightly different.

mstorrente

Thank you very much.

Do you think maybe enough changing the gasket between master cilinder and brake booster to recuperate vacuum?.

My problem is that "Bremskreis" (brake fluid pressure) warning light is on in my pod.

karl ruiter

I have a few thoughts here:

If your brakes feel good and the only problem is the warning light the problem is not in the booster. It would be either the master, the switch (on the master), or the wiring.

You can put in a 10" booster, but you have to hammer out the inner fender wall quite a bit to make it fit. I think this improves the feel of the brakes on the early cars quite a bit, but it is painful if you are trying to keep your car clean and stock.

If you still think the problem is the booster, and you want to stay stock, I have an almost new 9" booster that you can have. I found a new ATE part a few years ago, when I was unhappy with the brakes on m '79. I was still unhappy with the brakes after I changed the booster so I put in a 10" booster and a new master and then all was good. So the 9" booster is now sitting on the shelf. I think it has a few hundred miles on it. You would either have to pay shipping from Honolulu or, even better, come to Honolulu and pick it up. You could pay for your trip with what they want to charge you locally for the booster.

EC928NC

What an AWESOME offer for him Karl! I love this forum.

First though I'd go with swapping out the switches on the Master Cylinder. They are inexpensive, and you can do the job in less than an hour (unless you have Gorilla hands like me). Secondly, I'd try a new MC. I don't think the booster is bad from what you described.

See if that works first.

mstorrente

OK, thank you very much to all of you.

I think Iīll go to Honolulu to take the booster and if the car doesnīt stop, I wonīt mind....

Seriously, I think Iīll try with a new M.C. and the switches, they are easier to find and maybe the solution. Iīll tell you my improvements.

I think I will use this forum again, it is much better than Spanish ones...

mstorrente

I have a question...when you refer the "switches", are you refering the brake light ones....? wich is its funtion....?
Thanks

EC928NC

Yes. They perform a dual pressure fault/brake light function. Do a search on them here and you'll get a LOT of hits. Replace them both - cheap and easy... and in my experience (I replaced mine last summer), you don't need to bleed the brakes afterwards.