More clutch / brake master cylinder questions.

[Lukens]

I'm slowly getting an education. Randall put me onto some nice manual downloads... thanks again.
Ive got separate Girling clutch and brake MC's. I've disassembled both and honed the walls. I've got one repair kit and ordered another.
2 questions:

One of the plungers had a "plunger seal" AND an "end seal". One had a plunger seal only. I didn't notice this until I had both cylinders in pieces. Some of the manuals show the plunger with an end seal, some don't. The Moss repair kit diagram didn't show one, but one was included. On the other hand the diagram showed the spring washer and none was included. I called Moss and they said sometimes their supplier includes different items ??? Anyway, unless someone tells me otherwise, I'll put the end seal in both assemblies.

MC check valve. One manual states that only the brake side needs the check valve. Another parts diagram shows it on both the clutch and brake assemblies. Both of my cylinders had check valves. I can't see why it would hurt to have one in both.

BTW. I see VB has these MC's on sale for $40. Why the **** am I fooling around with refurbishing?

 

[LarryK]

That's why the internet is such a good parts source. It's just takes time to shop around and find the best buy with the least amount of shop time! But, now you must find out if you did a good job of refurbishing the old. If you did the work right, then the feeling of I can do it, but if you didn't, you have a back up plan that only you will know the outcome.

 

[TR3driver]

I'm slowly getting an education. Randall put me onto some nice manual downloads... thanks again.
Ive got separate Girling clutch and brake MC's. I've disassembled both and honed the walls. I've got one repair kit and ordered another.
2 questions:

One of the plungers had a "plunger seal" AND an "end seal". One had a plunger seal only. I didn't notice this until I had both cylinders in pieces. Some of the manuals show the plunger with an end seal, some don't. The Moss repair kit diagram didn't show one, but one was included. On the other hand the diagram showed the spring washer and none was included. I called Moss and they said sometimes their supplier includes different items ??? Anyway, unless someone tells me otherwise, I'll put the end seal in both assemblies.

MC check valve. One manual states that only the brake side needs the check valve. Another parts diagram shows it on both the clutch and brake assemblies. Both of my cylinders had check valves. I can't see why it would hurt to have one in both.

The Girling MCs work differently than the Lockheed ones do. That valve is not a check valve at all, it is what stops fluid from flowing back into the reservoir when you step on the pedal. It is essential to the operation of the cylinder. The Girling system is described in the TR3 addenda to the workshop manual.

By "end seal", I assume you mean the O-ring on the piston near the pushrod end. Girling apparently decided that there should not be a seal there. Later pistons didn't have the groove, and the Girling rebuild instructions say that if there is a groove, it should be left vacant.

I haven't checked recently, but it used to be that the replacement MCs did not look and fit the same as the originals. The casting is different and there is an adapter supplied to connect to the original brake lines (which means you have to bend the lines slightly). There was also some fuss a year or two ago about defective MCs being supplied. As I recall, Moss announced that they had pulled the defective units from their shelves. I didn't hear a similar statement from VB (and TRF was apparently selling a different cylinder that wasn't defective).

 

[Lukens]

That valve is not a check valve at all, it is what stops fluid from flowing back into the reservoir when you step on the pedal. Sounds like a check valve to me.
The O-ring on the piston near the pushrod end... Girling apparently decided that there should not be a seal there. The Girling rebuild instructions say that if there is a groove, it should be left vacant. Hmmm, do I toss the one that came with the kit?

Why did I think this would be cut and dried?:crushed:


QUOTE]

 

[CJD]

These pistons tend to be "sticky" in the bore. By that I mean that after a rebuild the piston is reluctant to return to the resting position under the return spring pressure alone. After a few miles they loosen up...but a second seal is just going to make them even stickier.

John

 

[Andrew Mace]

By "end seal", I assume you mean the O-ring on the piston near the pushrod end. Girling apparently decided that there should not be a seal there. Later pistons didn't have the groove, and the Girling rebuild instructions say that if there is a groove, it should be left vacant.

If memory serves, that change (deletion of the extra seal) happened in the early 1960s, which leads me to believe that the one cylinder you have with that groove and seal is original to the car. I know I had one such master cylinder on my 1960 Herald sedan and was intrigued by the seal/groove in same; it wasn't for several years that I came across a Service Bulletin explaining the deletion of the seal, etc., etc.!

 

[TR3driver]

Sounds like a check valve to me.

To me, a "check valve" is one that blocks flow in one direction only. But the valve in the Girling MCs allows flow in both directions when it is open, and neither direction when it is closed. Blocking the flow back into the reservoir when the brakes (or clutch) is applied is the most obvious function, but it is also important that it allows flow in both directions when the pedal is released. This covers both the expansion of the fluid when it gets hot (which could otherwise apply the brakes), and allows additional fluid into the calipers to cover the wear of the brake pads. Anyway, it's name doesn't really matter, my real point was just that it is an essential part of the MC operation and hence found in all of them, even the clutch MC (which is identical to the brake MC).

Personally, I would leave the extra seal out; and maybe not even use that kit. The presence of the extra seal indicates to me that either the kit is a copy by someone who didn't really know what they were doing (and hence there might be other problems) or else it is a very old kit. The "rubber" does get old, even still in the box, so using a 50 year old kit is probably not a good idea IMO. Also, back in the 60s and 70s, the Girling seals were made from an unusual rubber compound (some say it was natural rubber, I don't know) that was not compatible with many DOT 3 and DOT 4 brake fluids. You had to be careful to use Girling fluid, or the fluid would gradually attack and destroy the seals.

No, I didn't believe that either. But back in 1978 I did an experiment where I installed all new seals on my TR3A, filled and bled with fresh American DOT 4 brake fluid (Wagner brand as I recall), did a quick trip around the block to confirm that everything was working, and then left the car parked for about 3 months. When I returned, the reservoir was empty, and all the seals were gooey and leaking. What little fluid remained in the cylinders was visibly black, presumably with material from the seals. It made a believer out of me.

Later, they evidently changed the composition of the seals so the issue went away.

 

[Lukens]

Randall, I agree with your check valve definition.
As for the rebuild kit, I got it from Moss last week. The second one I ordered came today. Both kits included the "end seal' which I will leave off. Strangely though, the kits don't include the "wavy spring washer" that belongs in the valve assembly. This little spring closes the valve once the plunger leaves it's home position. One of mine is suspect. I'm assuming (hoping) that fluid pressure will hold the valve closed anyway.
Fishing this weekend so I'll find out next week (priorities you know).
Russ