DDK - Die Deutschen Klassiker

Going to replace the brake master cylinder on the S as I don't seem to be able to get a firm pedal anymore. Before you ask, done brake bleed several times, calibers refurbed so thinking its the master cylinder.

So my question, when you fit the new one, do you need to put some brake fluid in it first or do you just fit it and then bleed the brakes to get the air out of it?

Just fit it and bleed the brakes through.
Before you change it, have you bled both nipples on your "S" front calipers????
The sad voice of experience from years ago ............

JW

I have about 4 times now, still no better. Has the calipers refunded last year, pedal was fine before that but don’t seem to be able to get it back

No leaks evident anywhere, so thought good place to start would be the master cylinder

I would always bench bleed it before fitting a new one to the car. It’s easy, gets rid of 90% or so of the air in the new MC which means you are not pushing all that air into the system at the start and having to ensure you get rid of it all. I did this last year on mine and only had to go round once bleeding each caliper.

Job done, brakes are like night and day now, from very spongy to very hard pedal. Off for a drive now to try them out

Excellent!!

JW

Fantastic news.

I have to fit a new MC too - never done it before, or bled brakes before! Sounds like fun!

I don't see a seal on the parts diagrams, where the MC mounts to the bulkhead, but I feel like it should have one - can anyone say for certain whether it needs a seal please?

Thanks for reading and hopefully someone can answer...

Never fitted one on my '73T since the first rebuild in 1989. Does seem odd that there is no gasket there mind.
With the splash shield in place, that whole area is very well defended from road splash, so maybe Porsche thought a gasket pointless?
Easy to make one from a suitable material so why not fit one?

deano wrote:I have to fit a new MC too - never done it before, or bled brakes before! Sounds like fun!

I don't see a seal on the parts diagrams, where the MC mounts to the bulkhead, but I feel like it should have one - can anyone say for certain whether it needs a seal please?

Thanks for reading and hopefully someone can answer...

I’d recommend getting one of the pump-up pressure bleeding kits made by people like Sealey. Makes the whole process easier and very much a one-person operation

sladey wrote: ↑Fri May 19, 2023 5:12 pm
I’d recommend getting one of the pump-up pressure bleeding kits made by people like Sealey. Makes the whole process easier and very much a one-person operation

I'd second this - makes brake bleeding a doddle ...

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Lightweight_911 wrote: ↑Fri May 19, 2023 5:51 pm

sladey wrote: ↑Fri May 19, 2023 5:12 pm
I’d recommend getting one of the pump-up pressure bleeding kits made by people like Sealey. Makes the whole process easier and very much a one-person operation

I'd second this - makes brake bleeding a doddle ...

.

BUT remember to seal off the air vent pipe to the side of the brake fluid reservoir, otherwise when you pressurise the reservoir, it will p155 all the fluid out of that vent pipe, into the front frunk area!

Nine One One wrote: ↑Fri May 19, 2023 6:38 pm
BUT remember to seal off the air vent pipe to the side of the brake fluid reservoir, otherwise when you pressurise the reservoir, it will p155 all the fluid out of that vent pipe, into the front frunk area!

I probably would have discovered this the hard way, so great tip!! I think I will fit a seal too

I made a little paper gasket, probably not needed as Graham said.

As for the vent tube… no one would be stupid enough to make that mistake with a pressure bleeder would they…

sladey wrote: ↑Fri May 19, 2023 5:12 pm

deano wrote:I have to fit a new MC too - never done it before, or bled brakes before! Sounds like fun!

I don't see a seal on the parts diagrams, where the MC mounts to the bulkhead, but I feel like it should have one - can anyone say for certain whether it needs a seal please?

Thanks for reading and hopefully someone can answer...

I’d recommend getting one of the pump-up pressure bleeding kits made by people like Sealey. Makes the whole process easier and very much a one-person operation

Alternatively, you could just bribe a 19 yr old lad to sit and respond to on/ off, I find this works well but does cost a couple of £££ each time