Brake master cylinder adpator plate

GreatOldOne · #1 25th January 2007, 09:40

Guys,

I can sort of see what needs to be done with this - obviously the adaptor plate gets attached to the cylinder via some machine screws that sit in the countersunk holes in the plate and some nylocs. This connection get sealed by the rubber o-ring around the base of the cylinder.

Then the plate gets bolted to the servo, via the two studs on it. But the adpator to servo mating surface has no 'sealing' material - it's just metal to metal.

Am I missing a gasket of some sort? Pics of your setups would be good.

Cheers,

Jason

MartinClan · #2 25th January 2007, 12:12

I used a gasket intended for an SU carburetor! It was almost a perfect fit. I think others have sealed the joint using silicone but I am not sure how long that will last in an atmosphere with petrol vapours.

Robin

peterux · #3 25th January 2007, 19:35

Jason,
I was advised by Marlin to use silicone sealant.
I used good quality black RTV silcone sealant made by Wurth.

Peter

GreatOldOne · #4 25th January 2007, 19:54

Thanks guys.

Peter - how did you apply? just a thin bead around the circular aperture of the servo?

peterux · #5 25th January 2007, 20:03

Probably, it was some time ago I did this!

Peter

Patrick · #6 26th January 2007, 11:55

Quote:

Originally Posted by MartinClan

I used a gasket intended for an SU carburetor! It was almost a perfect fit. I think others have sealed the joint using silicone but I am not sure how long that will last in an atmosphere with petrol vapours.

Robin

Robin where can I get one of those from? I'm not happy using silicon as it started leaking pretty quick when I was still experimenting with the marlin servo

MartinClan · #7 27th January 2007, 10:09

Quote:

Originally Posted by Patrick

Robin where can I get one of those from? I'm not happy using silicon as it started leaking pretty quick when I was still experimenting with the marlin servo

Absolutly no idea! Mine was lying round in a box of old bits. I will see if I have another one.

Robin

GreatOldOne · #8 6th February 2007, 19:04

I've been looking at the master cylinder and servo again... I don't think I need to use the adaptor plate, as I'm using a remote resevoir - which is a good thing really, as my adaptor plate isn't right:

The counter sunk holes don't line up with the mounting holes on the cylinder!

However, whilst I can put the cylinder directly onto the servo, I'm not sure that the seal will be any good. The O-ring will seal most of the mating surfaces, but the cylinder itself has a notch cut into it on it's base:

Isn't this going to cause a leak? Or is this gap required?

peterux · #9 6th February 2007, 19:13

I used a BMW e30 master cylinder which fitted the adaptor plate just fine.

What master cylinder are you using? The gap will sure to cause a problem sealing it to the brake servo.

I think Patrick might of had the same problem?

Peter

GreatOldOne · #10 6th February 2007, 20:16

It's a marlin supplied part (as is the servo), so I don't really know...

My BMW master cylinder got waterlogged (I accidentally dropped it in a bucket of hot water when I was cleaning the outside) so I binned it as I couldn't be asked to strip it down - hence the new one.

Patrick · #11 6th February 2007, 20:32

That indeed is the Marlin one, I found with mine that I had a gap between the servo pin and the master cylinder - no brakes until the very bottom of the pedal travel.

Any gap or hole in the vacuum system is not good for the engine it will stutter and run very badly.

I tried to fill this gap with silicon, that didn't work. I ended up using a combination of rubber and silicon which held for a while.

Due to the pedal issue and vacuum leak I decided to go with the BMW master cylinder as it would be much easier to seal it up. The adapters that Robin is having made would have been needed in either case to make full use of the brake pedal travel.

GreatOldOne · #12 23rd February 2007, 08:38

I've managed to plug the hole on the cylinder. I just cleaned up the area with some carb cleaner to degrease it, and then slapped some JB Weld into it and left it to set. I then used my dremel to shape the patch to the same shape and radius as the base of the cylinder.

It's rock hard and bonded solidly to the metal, and seals well with the servo when used with the supplied O-Ring (I squirted some compressed air into the servo, and there's no leaks around the servo / cylinder seal). So that's a result.

Patrick · #13 23rd February 2007, 09:30

Nice one