brake master missing seal

[RestoreThemAll]

Does anyone know where to source what Moss calls a dust seal (closest to the push rod). See attached. In the cat they mention that its discontinued and not needed. At the very least it must help align things.

Also, in the pic, the rebuild kit came with two large round gaskets. What are they for? Not for my BJ7?

Dale

 

[vette]

Dale, I presume you are talking about the dust boot that is at the inboard end of the master cylinder. #6 in my pic. this is just a dust cover to help to keep dust and dirt away from the two inner seals and cylinder. Without the boot you'll just know when the inner seals are leaking sooner.
If it is not available from the usually Healey suspects, you could try a place like Summit Racing and just by one that has a similar diameter. Also, why don't you give Healey Surgeons a call in Tacoma Park, Md. They have a terrific inventory.

 

[British_Recovery]

Those seals are probably for the cap on the reservoir - only one is needed.

 

[RestoreThemAll]

Hey Vette,

Yes, that's the seal. I don't care as much about it being a dust seal. I think that the cap will take care of dust, and I'll wipe my feet before I get in the car, or not. I have to think that seal works in conjunction with the inner seal to keep the whole thing straight in the cylinder. Otherwise it'll pivot on the inner seal slightly. Not a huge deal but with time will cause wear. I did have my original girling masters brass sleeved so it may not be as much of an issue.

I'll check with Summit and Surgeons. Thanks for the tips.

I'm working hard to get this thing restored in 10 days. On average I work on it every 10 days!

 

[RestoreThemAll]

Thanks BR. I'll check for size and fit. There's two in each kit. Strange.

 

[steveg]

That item #8 has been discontinued. That's why you don't see it included in the Moss drawing. There were some problems with it causing brake or clutch drag by moving the piston slightly forward.
PS - Pegasus Auto Racing is the source for genuine Girling masters and rebuild kits.

 

[RestoreThemAll]

Steve,

Did you leave out the seal on your car? Are you recommending that I leave it off? I would like to learn from others experiences. This forum has helped me to avoid plenty of potential pain.

Dale

 

[RestoreThemAll]

I just checked Pegasus Auto Racing. They also don't supply the dust seal. Same with Healey Surgeons web site.
https://www.pegasusautoracing.com/productselection.asp?Product=3504

So do I put in an o ring or just leave it out?

 

[steveg]

Steve,

Did you leave out the seal on your car? Are you recommending that I leave it off? I would like to learn from others experiences. This forum has helped me to avoid plenty of potential pain.

Dale

Dale - A few years ago I had a situation where a new master cylinder in effect made it as if I were riding the clutch all the time. I wore out a new clutch disc in a year. I believe this seal was causing the piston to be just a little forward of where it should be, which had the effect of preventing the clutch fluid from flowing back to the reservoir. As I recall that MC had the seal and when I removed it, the MC worked properly. It must have been an NOS MC to have had the seal. With the external boot over the end of the MC, the seal does absolutely nothing anyway. No o-ring is necessary to replace it.

 

[RestoreThemAll]

Thanks for taking the time to explain your experience Steve. I'll leave the seal off

 

[Bob_Spidell]

... the effect of preventing the clutch fluid from flowing back to the reservoir ...

Hmmm ... not sure that's how it works (but, as usual, I could be mistaken). When you apply pressure to the pedal--brake or clutch--a small, spring-loaded seal at the forward end of the cylinder--sometimes called a 'foot valve'--closes the line to the reservoir (if it didn't, you'd push fluid back into the reservoir instead of to the slave cylinders). When you release the pedal, the piston retracts, the foot valve opens and fluid is drawn from the reservoir in order to 'refill' the M/C. Fluid should never be pushed into the reservoir; if this happens the foot valve has failed. In fact, the test for a failed foot valve is observing the fluid level in the reservoir and if it rises any at all when the pedal is depressed the foot valve is leaking (in effect, the foot valve is a one-way check valve). I got a lesson in this when the foot valve in my brake M/C was damaged somehow, and had to drive over a thousand miles having to pump the pedal a couple times every time I needed to brake.

This relates to the discussion on the Healeys mailing list about the small spring in the clutch master cylinder which can apply pressure to the graphite release bearing, causing premature wear to the bearing and/or the clutch disk. If fluid was allowed to return to the reservoir the pressure would be released, but you'd have other problems.

 

[steveg]

Hmmm ... not sure that's how it works (but, as usual, I could be mistaken). When you apply pressure to the pedal--brake or clutch--a small, spring-loaded seal at the forward end of the cylinder--sometimes called a 'foot valve'--closes the line to the reservoir (if it didn't, you'd push fluid back into the reservoir instead of to the slave cylinders). When you release the pedal, the piston retracts, the foot valve opens and fluid is drawn from the reservoir in order to 'refill' the M/C. Fluid should never be pushed into the reservoir; if this happens the foot valve has failed. In fact, the test for a failed foot valve is observing the fluid level in the reservoir and if it rises any at all when the pedal is depressed the foot valve is leaking (in effect, the foot valve is a one-way check valve). I got a lesson in this when the foot valve in my brake M/C was damaged somehow, and had to drive over a thousand miles having to pump the pedal a couple times every time I needed to brake.

This relates to the discussion on the Healeys mailing list about the small spring in the clutch master cylinder which can apply pressure to the graphite release bearing, causing premature wear to the bearing and/or the clutch disk. If fluid was allowed to return to the reservoir the pressure would be released, but you'd have other problems.

Bob - I think you're right and my reasoning was off a little. However I had a problem with the clutch being "ridden". Maybe it was a collapsed hose - I replaced it with an SS hose at the same time. That said, the factory removed that seal for a reason - maybe it was causing problems.