Stuck Clutch.

[RobH]

25 minutes ago, My Dads Car said:

That pushrod won't budge without the bleed nipple cracked open, at least a little bit...

Ah - this sounds like it could be a master-cylinder problem then.  You should be able to push the slave piston back without having to open the bleed screw but if the master cylinder pushrod is not fully releasing the master cylinder when the pedal is up, the fluid cannot get back that way.   That would explain why your clearance gap at the slave keeps closing up.  

There should be a small mount of play between the master cylinder pushrod and the pedal when the system is at rest. That ensures the m/c piston can retract fully.   On the earlier cars the pushrod is adjustable but I don't think it is on your car.

I have a vague recollection of a problem where new master cylinders were being supplied with the wrong length pushrods - has your m/c been changed? 

 

Edited August 14 by RobH

[My Dads Car]

This is the same master cylinder that was on the car when it last ran, same for pushrod assembly; it is not adjustable.

Since the system is now open I think I will pull the master cylinder as well (that bottom bolt though....) and see what's going on in there. I know I rebuilt it well over a year ago. Since I did not have the body tub to install it properly I filled it with fluid and set it aside in the bracket until May of this year...

[Z320]

At a TR4A it "must" look like this (indeed on my 4A it looks different )

 

The pedal not pressed pulls on the push rod, the free play is automaticly vio the mushroom head

 

[Z320]

49 minutes ago, RobH said:

Ah - this sounds like it could be a master-cylinder problem then.  You should be able to push the slave piston back without having to open the bleed screw but if the master cylinder pushrod is not fully releasing the master cylinder when the pedal is up, the fluid cannot get back that way.   That would explain why your clearance gap at the slave keeps closing up.  

There should be a small mount of play between the master cylinder pushrod and the pedal when the system is at rest. That ensures the m/c piston can retract fully.   On the earlier cars the pushrod is adjustable but I don't think it is on your car.

I have a vague recollection of a problem where new master cylinders were being supplied with the wrong length pushrods - has your m/c been changed? 

 

When he can pump the locking valve must be OK.

At my mate Michels TR3A we can't push the slave piston back, tomorrow 10:00 we fit a new one and look in the old on.

Edited August 14 by Z320

[My Dads Car]

Some good news - after completely breaking down the clutch hydraulics and re-bleeding the system as per Ralph Whitaker's solo method I can now engage first and second gears! I was able to engage third of with a bit of force two times but not always. Both fourth and reverse remain inaccessible, with reverse presenting some grinding noise as I go further into the slot.

What changed:

I finally put the car up on four heavy duty axel stands rather than test on the ground.

Upon removal the master cylinder pushrod was nearly impossible to push in fully. The travel was about half by hand, the remaining amount required me to lean into it with my entire bodyweght against a solid surface. I dismantled the entire unit and cleaned everything with brake fluid. Before I reassembled the MC I tested the pushrod, finding it much easier to push in fully, with an audible "pop" that sounded like the spring more fully seating on the opposite end of the piston.

I cleaned up the slave cylinder similarly, finding it much easier to push the piston into the cylinder when attempting to bleed.

I tried adjusting to pushrod to .25" (don't have a great .3 gauge and .25 was the closest I have to that. I was curious about the updated spec earlier in this thread)

I should have access to help later today to do a proper two-person bleed. I am hoping that will solve the remaing issue with third, fourth, and reverse.

Thank you for all your technical expertise as I worked thorough this problem! No way I solve this without the precise, nuanced insights you all shared

-Jamie 

[TR Rob]

My TR3A has am all synchro gearbox on all 4 forward gears but I presume not on reverse. I have found in the past it was difficult to select reverse without grinding the gears.

My solution is too fully depress clutch and then select second gear before then selecting reverse….no grinding

[Z320]

Hi,

this morning I first made a simple tool to check the orientation of the slave on Michesl's TR3A

 

Made from black POM d 25 mm x 10 mm and a threaded bar M10 it worked well on my old slave cylinder

Michel's slave cylinder look poor but was sealed, later after a good clean it looked OK, but the internal spring was missing

The metric nuts and bolts caused us some irritaion....

With the toll the orientaltion was definitely down to the lower drilling.

But out of line to the lever

We compare the TR3A with the TR4A bracket and still osed the TR3A one.

For a better result we slightly bended it on my DIY 20 to press (bever bend the aluminium flange of the gearbox!)

and got a better result

Installed all together and bleeded the system, but the clutch dig not work with about 10 mm stroke of the slave.

So we bleeded again with the slave hanging down, the nippel 100% to the top, air came out, we gained 13 mm stroke.

Sady this was still not enough to get gear in, endless bleeding had no better result.

Finally we adjusted the play down to zero again, and the car ready to go back on the street again.

Strange....? Im sure there is still air in the master.

Yesterday I changed my masters seal for testing a selfmade one from a club member on my 4A,

this was including bleeding an issue of 45 minutes (via my modified bleeding crew).

Sadly we can't fit that at Michel's TR3A with seperate reservoir.....

Ciao, Marco

 

Edited August 15 by Z320

[BlueTR3A-5EKT]

I like the additional tool to check the alignment and the bend or set you put in the steel bracket to correct the mis-alignment.  That slave will probably last much longer now.

Tell me.  Why did you choose to fit the slave cylinder on the gearbox side of the mounting bracket? - like a TR2. 

Was this because you felt all the misalignment was now removed, so a sorter straight push rod was adequate?

Venting the bore of the master cylinder with a home produced bleed screw, that makes good sense.  Would adjusting the angle that the master cylinder sits at have similar benefits?  I recall Spitfire had its master cylinders mounted at getting on for 20 degrees tilt from horizontal.  Many years ago I made tapered aluminium wedges that clamped between mounting bracket and master cylinder, to tilt the master cylinder on its mounting bracket of my car.  They are not fitted now as I have changed the system I use.

 

 

[Z320]

Hi Peter, 

we started to look for his clutch problem (sometimes it does not release) a few weeks ago.

I noticed the piston does not move further back in the salve cylinder and the push rod is too long to adjust.

So we cut it about 5 mm shorter, still with the same result, another - 5 mm with the same result.

Than we noticed we can push it back by manual force, with the push rod - guess what - 10 mm too short.

Our conclusion: the piston glues in the cylinder, and Michel wanted to fit a new one anyway.

So we fitted the new slave cylinder now on the wrong side of the bracket and the rush rod was fine.

Anyway, with an adjustable push rod, easy to make and propper adjusted, is there a wrong side?

About my bleeding screw, for those who did not notice:

The master cylinder bleeds all air down to the slave - if it is fitted horizontal!

But sadly it is fitted upwards, about 11° on TR4/4A and RHD TR6 (on the bulkhead)

And about 21° on LHD TR6' against the bulkhead! On ALL TRs air remains air in it (more or less).

I see no way to change the construction by a wedge, so I fitted the allen head M4 bleeding crew on top.

Ciao, Marco

 

 

Edited August 16 by Z320

[Z320]

 

[RobH]

Wouldn't it be easier to raise the front of the car to level the cylinder ?  You only have to do it once when first filling and bleeding the master. 

(not too difficult for 11 degrees but I admit 21 degrees is a lot)

[Z320]

It is not possible, I reported about 2 years ago

to level 11° -> lift the front 434 mm !!!

to level 21° -> lift the rear 858 mm!!!

 

 

Edited August 16 by Z320

[Charlie D]

 

Wouldn't it be even easier still not to bother doing anything at all?

How many tens of thousands of TRs with the master cylinders at an angle are there?

How many people have even  realised that the system is not 100% clear of air?

Does it matter?

Charlie.

[Z320]

If you browse this forum for clutch bleeding problems there are indeed no problems at all 😂

[My Dads Car]

Here is an update regarding my "frozen clutch" situation. For your reference: the car is completely off the ground on four sturdy axel stands. There is no interior installed, not even the transmission tunnel, which means I get a good view of both the lever and interface of the transmission to driveshaft.

I have bled the system with an assistant multiple times, dismantled/checked/cleaned the MC and slave twice, set the play at the slave to both .1" and .3", and utilized both the middle and upper holes on the clutch lever. I can see about 1/16 of "slop" where the clevis passes through the clutch pedal before actively pushing in the MC piston. These are my consistent results:

1. Engine running, shift lever in neutral, foot off clutch pedal = nothing moves
2. Engine running, move shift lever towards any forward gear (but do not engage), foot remains off clutch pedal = transmission turns rapidly. 
3. Engine running, clutch pedal depressed = I can access any forward gear with some difficulty, transmission turns at the same speed as the preceding step. Reverse is inaccessible due to nasty grinding sound.
4. Engine running, foot off clutch pedal, any forward gear already engaged = able to move shift lever out of any forward gear with ease. Reverse remains inaccessible

I'm guessing the time has come to remove the transmission and see what's going on in there?

Thanks in advance for any and all insights
-Jamie

 

[Lebro]

You clutch is clearly not fully releasing for whatever reason.

I guess it's gearbox out.

Bob

[Charlie D]

Could it be something odd about how the release fork is operating the release bearing?

Something fitted back to front?

[jerrytr5]

Try your experiment with the rear wheels locked, as they would be on the ground. Seems to me you are introducing gearbox rotation that wouldn't be present.

I confess not to have read this thread from beginning, so you may be well ahead of that stage.

Jerry

[My Dads Car]

18 hours ago, Charlie D said:

Could it be something odd about how the release fork is operating the release bearing?

Something fitted back to front?

Hi Jerry, I'm in the process of pulling the gearbox as it's entirely possible I mis-fit the collar (or used one for a TR4) and bearing, or perhaps even something on the flywheel side of the engine...

Jamie

Edited August 20 by My Dads Car

[RogerH]

Hi Jamie

 the TR4A bearing has a slightly convex forward surface.      The TR4 is flat

Make sure that the friction plate is the correct way round.
Make sure that the phosy Bronze bush is fitted in the flywheel

Have a look at the splined shaft where it goes into the GB extension piece. Make sure that the shaft and extension are concentric.

 

Roger

[My Dads Car]

1 hour ago, RogerH said:

Make sure that the phosy Bronze bush is fitted in the flywheel

 

Uh oh.... I don't think I did this.

How large is this piece? I've had a bronze bush about the diameter of one's pinky finger and about 1/2 as long lying around, not knowing where it goes.... Could this be the bronze bush you mentioned? I am out of thown at the moment, otherwise I'd send a photo. 

-Jamie

[RogerH]

Hi Jamie

sounds about the right size.  I do not think it would cause your problem but it could make a noise and cause the GB front bearing to
wear sooner rather than later.

 

Roger

 

 

 

 

 

[RobH]

You have to take the flywheel off to fit that bush, so you probably still have the old one in there. 

[Z320]

The bronze bush I remember d = 1“, long = 1“, drilled = 1/2“

It is not really inconspisuous

[Charlie D]

4 hours ago, RobH said:

...You have to take the flywheel off to fit that bush, so you probably still have the old one in there....

I thought that the bush was just bashed in through the front of the flywheel.

Does the bush fit in the crankshaft then, rather than in the flywheel ?