Another Clutch Problem!!!

[Jim McCrae]

I have a recurring major problem with the clutch in my Traveller which is puzzling me and would appreciate suggestions on possible causes and solutions.
The car is a ’65 model which has been fitted with an MG Midget 1275cc engine by a previous owner. I believe this is the complete engine, flywheel, thick end plate and clutch from the MG and the gearbox is the original 1098cc rib case. Clutch mechanism uses Morris Minor mechanical linkage.
I fitted a new Borg and Beck diaphragm clutch kit shortly after buying the car. This worked well – light and smooth in operation – but after a few hundred miles it started making a loud grating noise whenever the pedal was pressed. On removing the engine, I found that the noise was coming from the pressure pad in the centre of the clutch cover. The pad should be held firmly against the diaphragm by a ring pressed on to the pad from the flywheel side. This was loose on my clutch allowing the pressure pad to spin against the fingers of the diaphragm. All other parts (clutch plate, thrust bearing and pilot bearing) showed no signs of damage. I assumed that this was a manufacturing fault and fitted another new clutch kit.
300 miles further on, the same fault is starting to become apparent. I am resigned to having to replace the clutch AGAIN but I need to fix the cause before doing so. I had not seen any reports of similar problems until recently. This YouTube video shows a more extreme example of this fault where the pressure pad has become completely detached.
https://www.youtube.com/watch?v=4jbYYwXTahk&t=142s - See 19 minutes in to the video. He has diagnosed the cause as a missing pilot bearing. I have a new bearing fitted so this is unlikely to be my problem but the symptoms are the same.
Any suggestions would be appreciated.

[philthehill]

I would ditch the carbon thrust and fit a ball race release bearing.
https://www.morrisminorspares.com/clutc ... ch-p829573
I had to do this when I fitted the 1275cc engine and 1275cc Midget gearbox.
The ball race acted directly on the diaphragm fingers and not the pad.
The 1275cc clutch is so strong that the heat from the carbon thrust when the clutch pedal is depressed causes the carbon thrust pressure pad to fail.
You may have to do some fitting work to get it all to work correctly but well worth the effort.

[Jim McCrae]

Thanks for your comments, Phil.
I am not sure that the ball race would help - carbon bearing is used on the midget, the ball race is intended for a hydraulic clutch and I doubt that that ball race would work directly on the diaphragm. Having said that, removing the pressure pad and using the ball race (if it fits) would remove the source of the grating noise. It is worth considering.

[philthehill]

Well it all worked for me.
Quite a few manufactures do not have a carbon thrust acting on a pressure pad but have a ball race release bearing acting directly on the diaphragm fingers. For example here is a Ford diaphragm clutch cover with a ball race release bearing acting directly on the diaphragm fingers.
https://www.ebay.co.uk/itm/125918768204 ... R_i6hKCUYg

[Jim McCrae]

Thanks again, Phil.
All suppliers seem to sell the same Borg and Beck clutch kit. I haven't been able so far to identify any available kits which don't have a pressure pad on the cover. Can you remeber which clutch you used?
Jim

[philthehill]

Cannot remember at the moment but will try and find the details.
In the meantime here is the link to the ball release bearing fitted to the 1275cc Midget gearbox with hydraulic operation.
https://www.petermayengineering.com/pro ... aring-kit/
You could go halfway and only fit the ball release bearing as that would get over the overheating of the carbon release bearing plate.
If you still have concerns speak with Peter May. A very friendly and helpful firm.
I latterly went to a 7.5" competition clutch fitted to a modified flywheel.

[Jim McCrae]

Cheers, Phil
I am not sure that the carbon bearing is the root of my problem. I suspect that there must be other factors.
I will certainly contact Peter May for advice.

[oliver90owner]

My first question would be whether the correct diameter spigot bearing was fitted - I know that Ford used two different bearings back then. If the clutch friction plate drops when the clutch is disengaged, it may well run off-centre when the clutch bites - not good.

Clutching at straws here, as I’ve never experienced your problem.

[Jim McCrae]

Thanks for your suggestion, Oliver. I did fit a new pilot bearing from ESM which I assume is the correct one. I will bear this in mind and check once I dismantle the clutch (again!).

[philthehill]

Only the early 12CC Midget engines had a bush.
Later 12CC, 12CE & 12V engines had a roller bearing fitted in the rear of the crankshaft to support the first motion shaft of the gearbox.
https://www.moss-europe.co.uk/spigot-bu ... soc=417775

Below is the 1275cc spigot roller bearing as supplied by ESM
https://www.morrisminorspares.com/engin ... er-p830107

Whilst the photo below is of a Marina 1275cc crankshaft tail the roller bearing arrangement is the same for the Midget.

Marina crankshaft tail 1.jpg (82.97 KiB) Viewed 3311 times

If you have a bush replace with a roller bearing.

[Jim McCrae]

Now that is interesting! My engine is a 12CE. It was fitted with a bush when I bought it and I replaced this with a new bush when I replaced the clutch. Presumably the dimensions are the same as the needle roller bearing but clearly the needle bearing was fitted for a reason!
I'll add this to my list of things to change.

Thanks again, Phil

[Jim McCrae]

I spoke to a technician at Peter May Engineering. His opinion was that the pressure pad is probably damaged through excessive throw on the clutch mechanism. He recommends replacing the carbon release bearing with their roller bearing. This involves removing the pressure pad and allowing the roller bearing to act directly on the diaphragm fingers (as Phil said).

I have purchased a PME roller bearing (which arrived the following day) and hopefully will be able to re-use the existing clutch pressure plate .
I'll post an update after I have installed everything.

[philthehill]

Please post photos of the installation before mating the gearbox to the engine.

[Jim McCrae]

Update:
I have removed the clutch and have found no obvious problems: the carbon release bearing is intact, there is no sign of damage to the pressure pad or clutch cover. When I removed the pressure pad in preparation for fitting the roller release bearing there is sign of heating on the fingers (see photo below) and I think this is evidence that the pressure pad is spinning within the fingers (probably as a result of over throw on the clutch mechanism).
I have checked that the pilot bush is firmly in place and it seems unlikely that the flywheel could accommodate a roller pilot bearing.

Fitting the Peter May roller release bearing:
The roller bearing consists of a well made CNCed bearing holder and a roller bearing with a round face. The first step involves pressing the bearing onto the holder. I found this was a tight fit but after sanding the holder was able to tap in on. The bearing works directly on the clutch fingers so requires the pressure pad to be removed from the cover. This was easily achieved using a hacksaw.

Again the new holder was a tight fit on the clutch fork so I had to lightly file the fork to get a good fit and ensure smooth operation. The holder is held to the fork using wire clips. PME advise drilling small detents on the rear of the fork to secure the clips.

Once I have put the engine back, I plan to investigate the clutch throw and possible install a stop to limit travel. Update to follow.

[Jim McCrae]

I have now worked out how to include photos.

[philthehill]

Thank you for posting the photos.
I think that you are correct in that the cover pressure plate has been turning, the scoring as well as the discolouring of the fingers points to that synopsis.
Whilst not a problem the release bearing moves in an arc around the release lever pivot point. To get the release bearing to move concentrically (that is parallel to the first motion shaft) some suppliers of the modified release bearing recommend that the release lever pivot hole is elongated so as to allow the release bearing to act in a concentric manner. If the hole is not elongated the release bearing will slightly oscillate on the fingers.
I use the same release bearing but mounted on a different carrier which has the ability to allow concentric movement between the carrier and the 1275cc Midget release lever.
I am surprised that the flat clips used for retaining the 1098cc release bearing could not be used.

[Jim McCrae]

Phil, thanks again for your input. Your knowledge and experience is helpful.

When you mention elongating the pivot hole do you mean the hole where the release arm pivots on the gearbox casing or where the bearing carrier pivots on the arm?

I don't know whether PME supply the wire clips because they think that the bearing needs extra support, but the carrier is a tight fit on the arm so there is no space for the flat clips. I had to file the arm slightly to get the carrier to fit.

[philthehill]

The pivot hole for the release arm/lever.
I would suggest that the elongation required is no more than 1/8" (3/16" at most).
The elongation allows the release bearing to always spin centric to the fingers.
The pivot bolt will require a Nyloc nut. The bolt has to be loose in the elongated slot.

[Jim McCrae]

All safely back together and working properly. I will make some further adjustments to the clutch once the rain stops.
Thanks to Phil and others for their advice and suggestions.

[philthehill]

Well done