Clutch Pedal Freeplay

[AUSMHLY]

Hello all, BJ8.
I don't have any freeplay at the clutch pedal. Could this cause problems at the clutch assembly?

The new clutch release plate is heating up and turning blue. (photo attached, less then 100 miles) The throw out bearing is wearing too much.
I've installed a new clutch assembly, throw out bearing, new fork bushes, new stainless steel slave hose, new slave cylinder and master cylinder.
The clevis pin is in good shape as is the hole in the pedal arm. Very little free play

The only pedal free play movement is with the clevis pin. Should the pedal have more freeplay then that?
I'm assuming the throw out bearing is under more pressure with the release plate then it should have.
I am not riding the clutch. Please look at the plate, it doesn't show any wear. The release plate is blue.

 

[red57]

There is a snap ring inside the master cylinder that keeps the piston in the bore. The piston needs to be able to return to rest against the snap ring when you lift the pedal. This is the only upper limit to the pedal travel. There are no external/mechanical stops on the pedal itself so as long as the piston returns to the \snap ring, there should be no problems caused by the pedal and you should have little or no free play.

 

[dezand]

Since the clutch fork at the bellhousing does not have a return spring, the only force pushing the slave cyl back is from the clutch pressure plate. The release bearing touches the plate continuously, but should really not have much of a load when fully released, maybe a pound or less. This system could not have a return spring because it would push the slave cyl all the way back into its bore and result in a lot of pedal free-play. Clearly for your case there is a high enough load to generate a lot of heat. If you disconnect the slave pushrod and the fork moves back and forth freely then there has to be some issue with the hydraulics. Most of the aftermarket MC or slave cyl's are made in China now, maybe the surface finish of the bore is not smooth enough and hangs up when the clutch is released, or maybe the MC piston is not returning all the way. Are you using Silicone fluid? Silicone does not lubricate as well, I had an issue with the brake master cylinder sticking down only when bleeding the brakes due to silicone fluid. In normal use it is fine. No problem with the clutch system though. Just a thought.

 

[dezand]

Just remembered, forgot to mention the spacer plates where the MC bolts to the firewall. You may need more spacing out to allow the MC piston to come all the way back.

 

[red57]

The shims under the master will do nothing to help the piston to return to the end of the bore because there is no external stop on the pedal, the push rod/clevis rests lightly against the piston all the time. Adding shims lowers the pedal height, removing shims raises the pedal height, but the location of the piston in relation to the end of the cylinder bore remains the same.

 

[Healey Nut]

Did someone replace the pushrod in the slave cylinder with the “extended push rod” version when it didn’t really need it ?

 

[AUSMHLY]

I appreciate the prompt replies.

red57
thanks for explaining.

dezand
"If you disconnect the slave pushrod and the fork moves back and forth freely then there has to be some issue with the hydraulics." Fork moves freely.
"Are you using Silicone fluid?" No, using Prestone dot 4 synthetic.
"You may need more spacing out to allow the MC piston to come all the way back." Adding shims lowers the pedal height, removing shims raises the pedal height, but the location of the piston in relation to the end of the cylinder bore remains the same.

Healey Nut
New Moss Slave cylinder which includes the push rod. I don't believe it's the extended one.

Healey Nut, would a shorter or longer push rod put less pressure on the release bearing?

 

[John Turney]

Do you still have the original/previous pushrod? If so, compare the lengths. I can see a too long pushrod causing your problem.

 

[Healey Nut]

Do you still have the original/previous pushrod? If so, compare the lengths. I can see a too long pushrod causing your problem.

Exactly why I asked

 

[AUSMHLY]

Do you still have the original/previous pushrod? If so, compare the lengths. I can see a too long pushrod causing your problem.

Thanks John, HN.

I bought a slave rebuild kit and a new pushrod. Original push rod and new replacement
are the same length.

Being I have two now, should I shorten one and try it? How much should I shorten it?

 

[BobHaskell]

John, you determined that the pressure plate and thrust bearing dimensions (lengths along the centerline of the driveline) are the same as the parts you took off the car?

 

[AUSMHLY]

Original pushrod 3"
New aftermarket pushrod 2 15/16"
(both turned pressure plate blue)

New Borg & Bech HD (HE4562) round pressure plate 2 15/16" bottom to top of pressure plate.
I've used two new ones of these, both pressure plates turn blue 100-200 miles

Used Borg & Beck (no model) triangle press plated 3" bottom to top of pressure plate
I just installed this one. Notice the pressure plate is smooth and still natural steel color. I have not turned motor over yet.

I'm trying to figure out why the throw out bearing is turning the pressure plates blue, before I start the engine with this one installed.
Both units are 9 1/2". Both fit on my car. The triangle one looks like the model BJ8 owners uses. Someone mentioned the paint mark should be green. My paint mark is blue. Mentioned blue is Jaguar green is Healey. So I still may not have the correct one?

 

[AUSMHLY]

John, you determined that the pressure plate and thrust bearing dimensions (lengths along the centerline of the driveline) are the same as the parts you took off the car?

Bob, I'm original poster, Roger.
The throw out bearing does center over the thrust plate when making contact. I've attached photos in the previous post of the dimensions of the assembly .

 

[dezand]

The original pressure plates from B&B for the Jaguar and the big Healey have different part numbers. The Jag unit has a higher spring force to cope with the approximately +100 hp over the Healey. The parts had the B&B part numbers paint stenciled to them during manufacture and the spring painted different colors in a small area. All the new B&B units are dual purpose, they fit both the Healey and the Jag, thus the blue painted spring.
This would have no effect on your problem though, the Jag unit is just stronger. I recently converted my BT7 over to a diaphragm style clutch and I did notice that when released there was some pressure on the fork from the slave. The only thing pushing the slave piston back is the clutch itself, so when the clutch is fully released, there is no additional load to push the slave piston back any further. But for sure it shouldn't be so high to generate heat to turn the plate blue. Online it says steel turns blue at 575 deg F.
When everything is installed can you physically move the clutch fork / piston back by hand? how about with a long screwdriver for leverage? Should push back fairly easily.

 

[dezand]

If you remove the rubber dust cover from the slave cyl and depress the clutch fully, there should be a small gap between the piston and the snap ring. Probably about .03 - .06 inch.
I wonder if the slave is not made correctly (bore not deep enough) and the piston bottoms before releasing the clutch 100%

 

[dezand]

I have a used original B&B diaphragm pressure plate (green paint) that I just now measured on the bench . It measures exactly 2.5 inches in height.
From a previous measurement, the height is 2.04 inches when installed.

 

[AUSMHLY]

The original pressure plates from B&B for the Jaguar and the big Healey have different part numbers. The Jag unit has a higher spring force to cope with the approximately +100 hp over the Healey. The parts had the B&B part numbers paint stenciled to them during manufacture and the spring painted different colors in a small area. All the new B&B units are dual purpose, they fit both the Healey and the Jag, thus the blue painted spring.
This would have no effect on your problem though, the Jag unit is just stronger. I recently converted my BT7 over to a diaphragm style clutch and I did notice that when released there was some pressure on the fork from the slave. The only thing pushing the slave piston back is the clutch itself, so when the clutch is fully released, there is no additional load to push the slave piston back any further. But for sure it shouldn't be so high to generate heat to turn the plate blue. Online it says steel turns blue at 575 deg F.
When everything is installed can you physically move the clutch fork / piston back by hand? how about with a long screwdriver for leverage? Should push back fairly easily.

Hello dezand, the used B&B model I have with the triangle unfortunately has lost it's paint code number, it's stamped Made in England. I'll assume it's an original, but with the blue paint, Jag? Learning as I go. Bought cheap off ebay, who knows how old it is...60s - when?
I bought it to test if the triangle design vs the round release plate and different length fingers may be causing the problem.

 

[AUSMHLY]

If you remove the rubber dust cover from the slave cyl and depress the clutch fully, there should be a small gap between the piston and the snap ring. Probably about .03 - .06 inch.
I wonder if the slave is not made correctly (bore not deep enough) and the piston bottoms before releasing the clutch 100%

Hello dezand, I have the tranny out of the car, once I back in, I'll check that. Thank you.

 

[AUSMHLY]

I have a used original B&B diaphragm pressure plate (green paint) that I just now measured on the bench . It measures exactly 2.5 inches in height.
From a previous measurement, the height is 2.04 inches when installed.

My Round B&B 2 5/16"
My Triangle B&B 3"

Yours 2.5"

????