TR2/3/3A TR3A clutch problem

[TuffTR250]

Six to eight years back I put new clutch master cylinder, slave cylinder, and brake master cylinder on my TR3A, all using DOT 5 fluid. They have worked well until about the last 6 months. The brake master still works well, whereas I now have a clutch problem. The clutch system does not hold pressure. I have a speed bleeder on the slave and I have bled the clutch system about a total of 10 times over a 7 day period. After it sits about 10 mintues after bleeding, on the first press of the clutch pedal it moves about 3 to 4 inches before I get pressure, and then if I pump it 3 more times, I feel the pressure after 3/4 to 1 inch movement of the pedal (as it should). I do not see any Dot 5 leaks from the clutch master nor from the slave cylinder. Since I have made sure the push rods are adjusted like they were when the clutch was working correctly, I don't believe adjustment is a problem. Could the problem be that either the clutch master or the slave cylinder are letting the Dot 5 fluid bypass an internal seal? If that is the problem, how can I tell which clutch system cylinder is the problem? Thanks!
Bob

 

[Hamish Racing]

i have heard of dot 5 silicone incompatibility with some older system/seals here in the uk.
also if the system hasn't been properly flushed of other DOT fluids the addition of the dot 5 silicone can cause such issues.
could this be it ?

 

[sp53]

I would replace the master and probably rebuild the slave and leave the slave cylinder in place and just push the guts out and push new ones in, rebuild in situ. I do not know how to tell which one is the problem plus there seems to be problems with rebuilding some of the masters.

steve

 

[Sarastro]

Well, if you've bled the clutch ten times and that didn't solve the problem, it doesn't have anything to do with bleeding.

Since there's no leakage, my guess is that you have fluid seeping back through the seal into the reservoir. Part 1 in the figure below. It's a pretty common problem, and the solution is to get a rebuild kit for the master cylinder and rebuild its internals. (The figure is for the TR4 MC; I assume the TR3 works the same way.)

When you remove the MC, look down into it and see if there is a problem with the seat that the seal presses against. If so, it's best just to replace the cylinder.

 

[Jayplum]

i have heard of dot 5 silicone incompatibility with some older system/seals here in the uk.
also if the system hasn't been properly flushed of other DOT fluids the addition of the dot 5 silicone can cause such issues.
could this be it ?

Proper flushing is necessary when you change to a DOT5 or silicone they are not compatable. You would need to do this with a power flush not just pumping the pedal. Some use alcohol but that is also not complatable so you have a clean system but a second flush is needed using Dot5.

 

[Jayplum]

when you lose pressure, how is the level in the MC? If it is a leak, the fluid has two go somewhere. Pull the caps back to see. IF dry it is in one MC or SC where a cup is deformed and letting the fluid pass or is folded over.
Get a second person to get under the car , I get my wife to do this for me (yeah I'm kidding). Watch the SC for movement. IF the rod goes in and remains, there is a problem with the SC. IF the rod slowly come out, the problem is with MC.

 

[charleyf]

My only advice is that you if and when you change or repair components you do them one at a time. That way if it starts working then you know which one it is. One other thing to look for is the hose running to the slave cylinder. Is there any noticeable bulging of that hose? Not a likely thing, but it does happen.
Charley

 

[CJD]

+1 with Steve and Sarastro...if you have no leaks and you have bled it properly, the master cylinder is likely due for a rebuild. The slave will leak if it goes bad...although the leak can be delayed for a while as the rubber boot fills with fluid.

 

[Jayplum]

+2

 

[TuffTR250]

Thanks for all the quick reply's. Here are my responses to some. I put all new hydraulic cylinders (brake and clutch). pipes, and hoses on the car 6-8 years ago so all that was new. I used the old cannister but cleaned it thoroughly. The cannister is full of Dot 5, both the clutch and brake sections. I tried to check the slave push rod for movement as suggested by Jay , but I had no one around to help, and the push rod was stationary by the time I got under the car. I have squeezed and wiggled the rubber boots on the master and slave and no wet from them.

This afternoon, I tried something that I saw in an old forum thread from Randall Young.....I removed the slave cylinder spring and pumped the pedal without the spring attached. I then waited about 10, minutes and I still had pressure within one inch of pushing the pedal. Randall said this will work on a temporary basis but is not the final recommended fix. I don't know what the final fix was. This makes me wonder if, in fact, I've actually got the slave cylinder push rod adjusted correctly. In the manuals it shows adjusting the slave with the spring attached. Is that correct, or should the spring be removed for the adjusting step? Thanks!!
Bob

 

[CJD]

It is easier to adjust the rod with the spring removed, so you can feel the throw out bearing contacting the clutch more easily. I would have mentioned trying to adjust the clutch, but you made it sound like this happened quickly after functioning properly. An adjustment does not go out quickly. Also, 6-8 years is a noble life span for parts. In other words...they are no longer new!?!

Edit...it just dawned on me that you may have experienced the classic clutch fork pin failure. If you go to adjust and the adjustment is WAY off, that is your problem.

 

[TuffTR250]

Thanks John!
Bob

 

[Jayplum]

It is easier to adjust the rod with the spring removed, so you can feel the throw out bearing contacting the clutch more easily. I would have mentioned trying to adjust the clutch, but you made it sound like this happened quickly after functioning properly. An adjustment does not go out quickly. Also, 6-8 years is a noble life span for parts. In other words...they are no longer new!?!

Edit...it just dawned on me that you may have experienced the classic clutch fork pin failure. If you go to adjust and the adjustment is WAY off, that is your problem.

Let's hope that is not the case, although all together possible. It means pulling engine, trans or both.

 

[CJD]

I'm slow, but when you said Randall recommended removing the spring for a temporary fix, I finally remembered that was for the pin failure. I think Geo ran his car for years with a broken pin and a removed spring...Geo, are you out there? By removing the spring, the slave cylinder rod does not return fully, allowing the slave to essentially "auto adjust" the play added when the pin failed and the fork moved slightly. The master then pumps in the added fluid, and everything works again. The pin usually fails on a spiral, so rather than just shearing cleanly, it breaks and then the fork moves back and jams on the broken parts of the pin.

 

[sp53]

Hydraulic clutch leakage on a tr3 is a very fluid adjustment and a floating operation. The whole operation is interesting because it works in this spongy leakage that does not seem to burn stuff up and it is self- adjusting. I wonder if it is English by design, but is very clever. Yeh you can pump the pedal for more pressure when something is wrong, like air in the line. You can take the spring off the slave cylinder and it might work better because the return is slowed down and some of the old pressure gets left over the last take off or shift I guess. I am just thinking out loud.

Yeh I remember Geo’s story; I think he left the pin broken for years because he could make it work. I bet about half the trans I have removed from tr3's had a broken pin and no spring. But sure yeh they work better with everything working spring and pin.

steve

 

[Jayplum]

Hydraulic clutch leakage on a tr3 is a very fluid adjustment and a floating operation. The whole operation is interesting because it works in this spongy leakage that does not seem to burn stuff up and it is self- adjusting. I wonder if it is English by design, but is very clever. Yeh you can pump the pedal for more pressure when something is wrong, like air in the line. You can take the spring off the slave cylinder and it might work better because the return is slowed down and some of the old pressure gets left over the last take off or shift I guess. I am just thinking out loud.

Yeh I remember Geo’s story; I think he left the pin broken for years because he could make it work. I bet about half the trans I have removed from tr3's had a broken pin and no spring. But sure yeh they work better with everything working spring and pin.

steve

Only function of the spring is to draw the pedal back and be able to push a full column of fluid. Without it you can still get a firm pedal.