Clutch hydraulic gearing

[Steve1967]

Thanks John and Rory,

Yes I agree, I think its the activating lever being too far past its fulcrum point as a consequence of the thrust bearing/flywheel/clutch plate being too thin. A thicker or taller bearing would help push the slave end of the lever further to the front of the car increasing efficiencies. At the moment the force on the pedal is almost trying to stretch the lever rather than deflecting it, if that makes sense?

John, I think the spring is fine, its the proper part and is not as chunky as it looks in the picture, thats just the close camera proximity and it being in the foreground.

Steve, thanks for your PM. I have tried calling but no answer, will try again in a bit.

Thank you guys, you seem to agree its and engine out job so I may as well get on with it.

I shall let you know the result in a few weeks!

Steve

[Steve1967]

Guys I have spent a few hours under the car taking the exhaust off as stage one to remove the engine and while I was there I took a couple of photos through the inspection hole under the clutch. I don't have an endoscope so this isn't great but it does show what I have.

The thrust bearing appears to be the correct one, with the longer reach. I also took a few pics of the lever and hole again and have removed the spring for a better view. Its now on the ramp so I could take one from another angle.

What do you think? I have ordered another Bearing from SNGB and a new push rod as mine is quite scabby!

I previously bought a 1" slave cylinder from Rimmers as suggested by someone in a previous post so I may try that first as, to my eye's at least, it doesn't look as bad as I first thought. The activating arm looks about on centre point so its efficiency should be OK I would think? it looks worse from the outside because of the bend in its shape as it leaves the bell housing.

Can I ask your professional opinions again? Sorry to be a pain but obviously its a big decision!! Do you think it looks OK?

Many thanks

Steve

[rfs1957]

Steve, daft question maybe, but are you sure that on full depression of the pedal the operating arm isn't fouling the bell-housing ?

[mgcjag]

Hi Steve.....just to confirm is the clutch pedal too heavy or dosnt the clutch operate correctly.....I have the Supra gearbox and adaptor plate between gearbox and bellhouseing......I cut my adaptor plate so the clutch fork could move fully rearwards (whilst on the bench) as Rory mentions above is yours cut back far enough.......Steve

[Steve1967]

Hi Rory, unfortunately I took it off before I checked that, but it must be ridiculously close even if its not actually touching. The trouble is thats going to give no room for wear so I think I need a better solution.

To make matters worse the 1" slave cylinder I bought is u/s, although it looks the same, the lugs are too far forward and it wont fit, back to square 1.

My worry now is that if I do have the correct thrust bearing, and there isnt a longer/thicker one available, what can I do to fix this?

I guess shims behind the flywheel might help, but this is probably dangerous and a bad idea and may cause problems with the starter ring. Or a new flywheel? I only skimmed mine but I dont know how much material the PO took off with his angle grinder??

I seem to be chucking money and effort at this thing like crazy and not making a lot of progress just now. Im looking forward to the golf course opening again so I can have a rest!

..........Today has been a bad day in the garage!!!

Hi Steve, I just saw your note as I was finishing this. Yes, I took off quite a bit of material before fitting the engine so that the lever would have full range. Even if it was bottoming out though, it wouldnt explain why its so heavy. It really would be hard to live with. It must be twice as heavy as my Healey clutch and thats not a lightweight by any means.

[mgcjag]

Hi Steve.....is there a problem with the pedal etc.....it you open the bleed nipple on the slave the pedal should move freely....is there something restricting it.......think you need to try a members clutch at least to give you a guide as to how yours should feel...Steve

[MarekH]

Steve,

If I understand you correctly, the clutch works but is heavy. I presume the clutch bite point is not very far down the pedal travel as you you press your foot down. If that is the case, then fitting a smaller master will mean your bite point moves down as you gain the mechanical advantage of the swap in the ratio of the cross sectional areas of the masters.

You appear worried about the clutch fork coming out in the middle of the hole in the bell housing, as opposed to being at one end. The 6 cylinder car has it's clutch fork pivot very near to the hole in the bellhousing, so full motion of the clutch moves where the clutch fork sits in that hole much less than you think.

How ratty the pushrod looks is of no consequence - it simply needs to have a rounded end at the cylinder end and enough threads at the other end to allow the freeplay setting to be correctly maintained. The release bearing photo appears to show it has plenty of carbon on it.

In summary, this thread hasn't moved on from its first post yet.

kind regards
Marek

[MarekH]

To my mind, the essential point to grasp here is that the actual sizes of the X-Y mechanical advantage within the clutch are orders of magnitude greater than the very small Z dimension that represents the disengagement travel necessary to free the plate from the flywheel.

In this context, the travel of the release bearing is much more significant in relation to the sizes of the "levers" that are in play, and upsetting the intended geometry by starting off in quite the wrong place will have a much greater effect on the effort required.

I don't quite get this - if the free play is set correctly, then the release bearing is always in the same place. If the release bearing is too far away, then this doesn't affect how hard it is to push the clutch in, you just just push very easily until it touches and then you do "the work" anyway, against the same big spring as you would any other time.

Steve may wish to check whether his master cylinder pushrod is scoring the master cylinder and is hard to push in regardless of whether there is fluid in the cylinder or not. If the pedal is poorly aligned to the master, then it will be hard to push in. This is because the pedal moves in an arc but the pushrod wants to travel in a straight line - the two don't have that much overlap and it is easy to overlook this if there are any non original factory parts fitted, e.g. auto to manual swap.

kind regards
Marek

[steve3.8]

A starting point would be to remove the slave clevis pin then reassemble with the slave return spring fitted to test the function of the hydraulics separately from the clutch ? , taking care not to exceed the stroke of the slave cylinder.
Your installed thrust bearing looks the correct one for a 9½" clutch in a "standard" setup.
I removed my engine last week and have 2 new clutch kits [AP + borg] on the shelf , my old and 2 new thrusts all match in heights , they appear the same height as yours and the one on the right in post 17.

L-R Borg --- Old[minus carbon] ---- AP

That eliminated you can then move to the gearbox.
Hope this is of some help.

[MarekH]

A starting point would be to remove the slave clevis pin then reassemble with the slave return spring fitted to test the function of the hydraulics separately from the clutch ?

Yes - at last - hallelujah !!

You are either doing the right work with the wrong mechanical advantage or you are doing the wrong work. If the movement is stiff already with no load, then that needs to be sorted.

My starting point would be to test just the pedal/master by putting a nice long hose over the slave bleed nipple and thus taking the slave, its seals, springs, etc, out of the equation, i.e. zero hydraulic pressure but no need to rebleed the clutch so you can check the mechanical action of the pedal and master. If that is super easy, then I'd test the slave/pushrod by adding that back into the equation, i.e. your "starting point". Then I'd take a drill bit which has the same diameter as the pushrod free play quoted in the manual and pull/push the pushrod to compare against and determine whether the free play is set correctly.

Now your able assistant can reconnect and pump the clutch all the way as you observe whether the fork movement is within limits, so you are happy with where the fork sits at rest and that it doesn't foul anything when disengaging.

You can put the rear up on blocks, have your assistant push the clutch in and determine that the engine and gearbox disengage fully if the rear wheels are turned. You ought not to have too much difference between a car in neutral and a car in gear with the clutch depressed - the difference is you'd be moving extra gears and have the mainshaft turn in the release bearing.

Now you take a view as to whether you were doing the right work with the wrong mechanical advantage or doing the wrong work and start spending money accordingly. Spending any money before going trough the above doesn't necessarily fix the right problem. You may find that the master cylinder pushrod wasn't lined up with pedal well enough and a washer under one of the mounting studs was all that was needed.

Doing the wrong work is also possible if parts are mismatched. Typically one purchases the clutch, release bearing and pressure plate all as a kit so they are from the same supplier. Mixing and matching may work, as might getting a new clutch pedal from a bloke on ebay - or it may not....

kind regards
Marek

[Steve1967]

Thank you guys. I have spent the day undoing all my hard work and stripping the engine ancillaries. It will be coming out in the morning. As such I didn't do everything you have suggested today but I can tell you that when bleeding the clutch there was no effort required on the pedal so the hydraulic mechanism was working ok.
I shall report back on my findings tomorrow or Monday.
Thanks again!

[abowie]

Look I've just skim read this thread so I may have missed the point but isn't the likely cause of your problem that the adapter plate has changed the geometry needed for your standard clutch fork?

So when you put your foot on the pedal you have lost mechanical advantage and the clutch is heavy?

If this is the case, is it possible to make a modification to the clutch fork in situ rather than removing the engine? It might be as simple as making an adapter piece or welding material to the fork.

If it doesn't work well then you're stuffed and out comes the engine but if it does it might well save you a lot of trouble.

And if it fails you just lose your clutch, knock it into neutral and tow it home...

[abowie]

This is the slave and fork position on a 4.2 box.

How does it compare to yours?

[abowie]

Final comment. Can you just leave it and see what it's like when you drive it? It might be fine... and if not you've lost nothing by waiting.

[steve3.8]

Steve , just for added info to check out , a standard new centre plate is 9mm thick , a worn one 7mm , my thinking is your toyota centre plate could be too thick ? maybe trapping the diaphragm.
Although its not possible on a standard clutch to fit the centre plate the wrong way round also check the orientation.

[PeterCrespin]

Nice review Rory, although in the illustration the most important lever is missing.

It’s the sealed-for-life, rust proof ‘composite’ lever with built-in actuators, linkage, sensors and wiring. The correct functioning of said lever has a major effect on perceived effort, smoothness and controllability of both diaphragm and coil spring clutches.

Your wife displayed a particularly fine example, complete with a spare, although they appeared to be installed back to front in the footwell?

[ysmalkie]

I too seem to have a problem with the Borg & Beck Clutch on my 3.8 engine.

When I assemble my clutch to the flywheel, the diaframe of the clutch gradually pushes in util it's flat, or even concave.

When the gearbox is in, the fork is much further outward - then on your photo. I can disengage the clutch using a bar, but it's really hard even with a 1 meter bar.

Could this be the clutch problem? It seems as though the clutch steel plate is too thick and either skimming hte plate would help. But it's a new clutch!

What's wrong??


Tadek

This is the slave and fork position on a 4.2 box.

How does it compare to yours?

[mgcjag]

Hi Tadek....im assuming your photo is the lower one.....normaly the fork should be approx in the center of the square hole.....as mentioned in above posts have you used the correct release bearing...Steve

[ysmalkie]

Yes, it's the tall one, as on the photos above.

Tadek

[Steve1967]

Well, that was a nightmare!

As you saw from the earlier photos I had previously fitted a Toyota W58, 5 Spd gearbox. This, together with the adapter plate, is about a foot longer than the standard box, and bulkier. When I fitted the engine, I built the engine frames around it to avoid the heavy lifting. No problem, it worked like a charm. Getting the bugger back out again was another issue.

I have a one-post ramp so I tried dropping the engine down and lifting the car - no good - even with all the pulley's and water pump off. I tried lifting it up and over - no good. In the end the only way it would come out was by dismantling the picture frame/suspension/steering and lifting it on a shallow incline to clear the tunnel and the lugs on the lower front engine frames. By then of course I had stripped the engine of its carbs and manifolds etc etc. A pile of work I hadn't foreseen. I think the car hates me!

Anyway, back to the clutch, what I found was a combination of your suggestions above. Thanks to those who supplied measurements. My Toyota clutch plate was about standard to the jag one so no problem there, but the flywheel was about 2.0mm thinner than standard. My fitted thrust bearing was identical to the new one I ordered so I located another that was about 3mm deeper, (the casting was the same but there was more carbon on it). I also could see that the fork would foul the adapter plate (which is about an inch thick) at the end of its travel so I gave this some significant surgery so that the fork will now travel all the way back until it hits the housing, if required(?).
I checked the throw on the starter driving gear and there was 2 mm spare so I ordered an extra flywheel tab washer and fitted this as a spacer behind the flywheel. This almost made up the difference. I tested the flywheel with a dial gauge to make sure it was all true. Perfect!

I also replaced my horrible rusty slave push rod too.

Anyway, I have put it all together. The clutch lever is in what looks like the correct position now. I tested the clutch while the engine was on the floor with a couple of spare meters of pipe. It was considerably easier. While I was doing that, I tested it with and without the rather robust return spring that a few of you commented on. It was noticeably lighter without it - not in a major way but you could certainly feel it in your foot. I stretched the spring slightly so that it still worked but was slack at rest, another slight improvement.

While I was at it I also fitted a spacer on the clutch master cylinder to lower the pedal as it towered above the brake pedal in the footwell. This worked well and there is still room under it when the clutch is fully engaged.

So the engine went back in in just a few minutes and I am now refitting the picture frame etc. What a saga, but I think worth fixing it now rather than later. I would never have been happy with it.

Thanks for all your help, particularly Steve, Tadek, Steve 3.8, Andrew and Marek and the other contributors. I really appreciate your advice and help.

My best regards

Steve