Clutch not completely releasing - master and slave cylinder sizes?

[William Lewis]

Bob, the puzzling thing is everything worked great before I changed the Series 2 gearbox for a Series 5. I think I am getting too much throw in the clutch and I can back off on the slave rod a little to stop the whirring sound when I push the clutch all the way to the floor, but that won't help me get it into gear. My understanding is that all the gearboxes are interchangeable. Bell housing/clutch/flywheel all need to be swapped as a unit, but mine is unchanged from before the gearbox swap.

 

[howehap]

I think the clutch fork lever is different. There are a few discussions on this topic
-Bob

 

[howehap]

I believe the piston diameter for slave/master and the fork are different for series 2 vs series 3, 4, 5. I agree that the gearboxes are interchangable. Can you get it into gear if you don't push the clutch all the way down?

 

[MikeH]

Just curious and you didn’t mention it. Did you ever try to shift into 3rd or 4th with the engine running? I had a problem with a pinto where you couldn’t shift into gear with the engine running. This is a cable driven clutch. The problem was a spring from the clutch disk fell out and into the pressure plate. Made for a stiff pedal. Tore it down and put it back together with a new lever (retaining clip was broken) and didn’t notice the missing spring the first time.

 

[Wayne67vert]

When you installed the slave cylinder, is it mounted on the transmission side of the bellhousing?

 

[Tom H]

Good question, Wayne. I noticed that Bob Howe mentions at least once that HIS slave is mounted on the "correct" side, but he never stated which side he thought was correct. The only place that the WSM indicates which side is correct is in the dwg Fig 4 on page 6, Section D of WSM145, where it shows the slave mounted on the engine side which we know is the WRONG side.

Tom

 

[howehap]

If the slave cylinder is mounted on the wrong side (engine side) the slave piston will pop out of the cylinder. So I don't think that is the problem.
Here is a link to a thread from somebody that did not have enough throw (only .25" instead of .5" and the clutch did not disengage)
http://forum.sunbeamalpine.org/index.php?threads/clutch-woes.26267/
The thread discusses required clutch throw, MC to slave cylinder piston ratio calculations, and clutch release fork pedistal height of series 2 vs later series transmissions. It is worth reading.

William has .75" of throw, and his statement said "I have 3/4" travel on the slave rod. With the clutch pedal all the way down, I get a whirring grinding noise and the car wants to creep while in gear. Let up a little on the clutch pedal, grinding noise abates and the creep is better. Let up more and the clutch starts to engage smoothly". Every thing I have read says that on later series cars with all matching components, should have about .5" of slave cylinder travel to fully release the clutch. I think William may have too much throw and it is causing the pressure plate to go past "full release" start contacting the clutch disc.

 

[William Lewis]

Slave is on the tranny side of the bell housing.

It will shift into 3rd and 4th, but it is difficult. Even into 2nd when first starting up but then gets harder as it warms up. It shifts easier when I let up on the clutch pedal a little and the grinding whirring noise goes away. I think the throwout bushing may be bottoming out in the pressure plate or dragging on the tranny input shaft when the clutch pedal is pushed all the way down causing the whirring noise. With the clutch pedal all the way down, the car will actually start to creep while in gear. Let up a little on the clutch pedal and it stops creeping. Let up a little more and the clutch starts to engage. The throwout moves in an arc described by the motion of the clutch fork.

When I was bolting it all together, it seemed like the forks on the pressure plate did not sit as high as the one I had removed. That may be because the old clutch had worn and the old pressure plate was a very old one that had been turned once. If the clutch wears down a little, the forks on the pressure plate will sit higher and that may give me more room to release the clutch before the throwout bottoms out in the pressure plate or drags against the tranny input shaft.

I just pulled the tranny filler plug and the oil is foaming something fierce. I assume that is because the oil I put in was detergent (even though it said non detergent) or incompatibility with the oil that was used when the tranny and OD were rebuilt. I am going to change the oil (problematic because California has outlawed SAE30ND oil). I don't know if that will solve my problem, but one step at a time.

Does anyone know if compressor SAE30 oil is the same as SAE30 motor oil? Compressor oil is available in California, but motor oil is not. I'm not sure if compressor oil may have some additive that is bad for the brass in the tranny or may cause a problem with the OD clutch. Both kinds of oil are labelled API SA/SB. Of course, I can always ship in some oil, but none of the auto stores or even Tractor Supply will ship because of the regulations. Walmart seems willing.

 

[howehap]

Can you summarize again what parts you kept, what parts are new? which parts are series 5? Still sounds like you have more slave cylinder movement than is normal.
I believe the clutch disc goes in only one way, I wonder if it would bottom out if it was put in backwards? The car series 5 I'm working on had 90 wt oil in it. Changed it to SAE 30 detergent, only slight difference in shifting. I would be surprised if 30 wt detergent vs non-detergent will make any difference.

 

[howehap]

Another thought. When yu first put it together, you might have still had a little air in the clutch hydraulics (resulting in a little less slave rod movement). After you drove it a while any air will work it's/ bleed it's way out (you now have .75" slave rod movement).

 

[Tom H]

With the clutch pedal all the way down, the car will actually start to creep while in gear. Let up a little on the clutch pedal and it stops creeping.

Clearly the throw is MORE than needed.

 

[pruyter]

I think that a possibility is that the central boss of the pressure plate is wrong which causes the clutch going over the centre. The sympton with this error is that with a fully depressed clutch pedal the clutch won't work as it should while when the clutch pedal is not fully depressed all is okay again.
This error is commented in extenso by Tim Raymond in the UK on the forum of SAOC.
I remember him describing his experiences on the old forum of SAOC and it took about "ages" and several times taking out the gearbox before he finally found the cause of this error.

Regards,

Peter

 

[William Lewis]

Peter's explanation makes sense to me. I suspected something like that. Any cure other than pulling it all apart and replacing the pressure plate?
To answer others' questions, I have rebuilt the master and installed a new clutch slave. Bled the system well. If I had air, I would be getting less throw than I have.
My motor is a Series 5 and is unchanged from before the rebuild. My flywheel/bell housing/clutch fork and pedestal are all Series 1 and unchanged. I replaced the pilot bushing, clutch, pressure plate, and throw out (all Series 1). The clutch can go only go in one way as I checked that while I was installing everything. The transmission was a Series 2 and is now a Series 5.

 

[nsbluenose]

This happened to me on an MGB. Long story short, turns out it was the flexible rubber portion of the clutch line. The inside of the rubber hose was collapsing. Pushing the clutch pedal forced fluid through the hose but when the pedal was released the fluid would stay under pressure. Don't know what setup is on your car, but if there is a rubber pressure you may want to check it.

 

[gary1725]

I may have missed this amongst the long thread - I had a similar problem and from experience I can confirm that one problem could be worn thrust bearings - basically some of your clutch travel is doing nothing more than pushing the whole crank forward.... I replaced mine from underneath (not recommended) and it helped for another year until I had the engine out, rebuilt and I could properly set the drift clearance on an engine stand.

If someone else has already said this sorry for the repetition..

the clue for me was - it was never great but was working before - so miss matched parts kinda felt like the wrong path - I pulled the gearbox assuming a worn friction plate problem and while replacing it and the pressure plate helped it did not solve the problem 100%.. the replacement of the thrust bearings helped more..

 

[howehap]

William,
I did some research, the workshop manual WSM124 clutch section page 4, 5 states that there are adjustable slave cylinders used on series 1 Alpines. These slave cylinders with the adjustable push rods, and are mounted to the front of the bell housing (engine side).

All of the later series alpines have non adjustable slave cylinders and they are mounted on the transmission side of the bell housing.
I will cross my fingers this might be the simple fix that you need.
-Bob

 

[William Lewis]

To answer questions: My clutch lines are all steel and no rubber. At first, I had the slave on the engine side of the bell housing. Swapped it to the tranny side. Didn't help. I sure hope it is not thrust bearings. I doubt it as I rebuilt the motor only a few thousand miles ago and my clutch worked great before I replaced it after my tranny failed.
After slipping the clutch a bunch, I can now get it into 2nd gear. 3rd and 4th are slowish, but work reasonably well. First gear is still resistant and reverse grinds. I think I am having the problem that Tim described with the clutch barely releasing before it then gets pinched by the arms on the pressure plate. There is this fine space in the clutch pedal travel where just enough works and too much causes a grinding sound and the clutch binds again. I don't want to pull the tranny again, so I will keep slipping the clutch until I smoke it or wear it down to where my set up works. I probably only need a 16th or so more of release to make it work.

 

[howehap]

William,
I measured the non-adjustable pushrod for the series 2-5, it is 5.625" from the clevis hole to the end of the push rod. Don't know how long the adjustable pushrod for series 1 is, but i'm sure it is longer because the slave cylinder is mounted on the other side of the bell housing. Do you have the adjustable pushrod? Do you have any free play in your slave cylinder pushrod? If the pushrod is too long it will be pushing on the pressure plate and there will be very little clutch peddle movement before the clutch releases completely.

For the series 1, the pushrod is adjusted to give you about 3/32" of freeplay on the pushrod. The slave cylinder is mounted to the engine side of the bellhousing. See workshop page below.

 

[howehap]

Still trying to figure out why the clutch still doesn't release completely (enough drag so it grinds going into reverse and hard to get into 1st with engine running). This is a continuation of investigation. Slave cylinder piston is flush with back of housing, clutch rod is 4" long from end to centerline of lever pin hole. While waiting for the radiator to take care of the overheating problem, I pulled on the transmission to take a look at the clutch. Disc looks new, installed correctly, appears to be correct part. Pressure plate looks new, no visble issues. Fork and throwout bearing look correct and in good conditions. Pedistal mount is about 1 3/4" from base to pivot pin. Inside of bell housing coated with oil, disc does not appear to be coated with oil. Will be cleaning disc and mating surfaces with brake cleaner to be sure. I will try to check crankstaft end play (will this verify that thrust bearing is ok?)
Open to suggestions on what else to check before I put it back together. I can post photos

 

[Tom H]

Have you/we not concluded that somehow the clutch hydraulics are moving too far? You say it's OK if you back off the clutch pedal a bit. That tells me the pedal and hydraulics are moving it too much. I still suspect the non original Master. Have you measured its bore? Oversize bore would push the clutch too far.