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MG MGA - Clutch Adjustment

Hi Chaps. I am a relatively new MGA owner - bought my 1600 Mk ll 2 years ago. There was a problem with transmission drag with the clutch depressed, so I decided if the transmission had to come out, I would have the Hi-Gear 5-speed conversion. Osselli did this for me. When I got the car back, the clutch was biting very close to the floorboard, so I tried to bring this back up a bit by adjusting the master cylinder pushrod. However, this was at the end of its adjustment. I have cured this problem by making up a piece of threaded steel tube (5/16x24 UNF) to extend the rod. Question is - have other owners had this problem at all, and what did you do about it, and is my solution likely to be just a temporary one? As I recall, the wear on the release bearing and on the plate linings should cancel each other out. Comments gratefully received. (Picture attached). Thanks chaps. Adrian Bennett.
PS - As you will see, I had to file the width of the locknut down to allow the threaded tube to be as long as possible, but realised when I had done it a tappet adjusing screw locknut would have saved me a lot of work ....... ho, hum.


A Bennett

It looks like you may just be compensating for wear in the pedal to pivot and clevis with respective bolt, pin, etc. If so then you should be ok (although it would be better to re-bush etc.

If you measure the pushrod travel at the master cylinder between rest and full clutch engagement, (or is there any movement at the pedal before the pushrod moves?) we can compare with our cars.

If you are compensating for wear at the slave cylinder end then it's more serious and you need to checj that the release arm to pushrod pin and holes are not too worn.

Neil
Neil McGurk

Similar to disc brakes, under normal operating conditions the MGA hydraulic clutch is self adjusting there is no adjustment for wear of the clutch plate or throw-out/release bearing. The adjustment at the master cylinder is only to ensure there is a small free play (1/32") between the resting position of the pedal and when the pushrod in the master cylinder is first engaged. If the clutch is engaging/disengaging at an unusual location, then either there is air in the line, excessive wear in the clevis pins or corresponding holes in the yokes at the master or slave cylinder, or perhaps the piston cups (seals) are bad. None of these requires removal of the gearbox to repair. The gearbox need only be removed if the friction plate or throw-out bearing friction surfaces are worn to the point that metal-to-metal contact might occur, or have become burnt or fouled resulting in clutch slipping or grabbing.

Steve
Steve K

It is possible for air to get trapped in the end of the slave cylinder which can give the syptoms you describe.

It may be worth bleeding the slave cylinder again and during the operation make sure the slave push rod goes all the way in. This is usually done with the aid if a bar placed between the crossmember and the push rod.

While the bleed nipple is open push the rod fully home using the bar and see if any air is displaced before closing the bleed nipple again.

Regards...John
J Bray

Adrian,

As it may not be clear from the several responses you received, it is recommended that you remove the extension you added to the pushrod, identify the cause of the problem, and affect the necessary repair. To be explicit:
1) Remove the home-made extension.
2) Check for excessive wear in the pivot/bearing surfaces at: the pedal, the master cylinder pushrod yoke and clevis pin, and the slave cylinder pushrod yoke (hole) and clevis pin. If any of the round holes have been worn into an oblong shape, or the clevis pin is deeply cut, repair or replace them. (As Neil indicated, at best your home-made extenstion is a temporary compensation for the accumulated wear of one or more of these parts. At worst, you have no free-play and are not getting the full action of the piston in the master cylinder.)
3) Adjust the master cylinder pushrod to achieve the recommended free play of 1/32" (0.8 mm). (When being depressed, the clutch pedal should move freely about an inch from its rest position before you begin to feel the pedal work against the master cylinder pushrod.)
4) Bleed the hydraulic line free of air, and check that the slave cylinder pushrod is moving. (This is most easily done with two persons.)

If any of this is unclear, please let us know and we can provide more details to guide you through it.

Steve
Steve K

Here is a picture to go along with Steve's explanation. #1 top right are two rod ends (yoke) one is new one has oval holes. #2 is the end of a clutch pedal it also has an oval hole.#3 is a clevis pin that is quite worn. These three parts go together. There can be over a 1/4 inch of extra free play in these pieces. The rod ends and the clevis pin are available new. The pedal can be welded up and re drilled to repair it. # 4 is the slave cylinder rod see the oval hole. It also has a clevis pin that wears. The other point of wear is the bolt inside the trans that mounts the clutch arm. (sorry no old one here to picture) It wears on both sides like the clevis pins. The transmission must be out to replace it.
The slave and the bolt in the trans do not apply to the 5 speed.


R J Brown

Thanks chaps. Quite a bit to consider here. The car was fully restored in the 90s (I have the photo record), and has done just 11k since. I have checked out the pedal/master cylinder end, and there is no perceptible wear in the yolk/pedal, and I fitted a new clevis pin. I haven't checked the slave cylinder end yet, but I know Osselli used a new release bearing and clutch fork bolt, and there was a new bell housing as part of the 5-speed conversion. Air trapped in the slave cylinder is a possibility which I will look into, but pumping the pedal made no difference - but then I don't know if it would ..... Incidentally, Osselli mentioned that they had some trouble with the making the clutch work, and had to use some MGB parts to get it to operate properly - another possible factor? Thanks again, Adrian B.
PS Phew!! what a rogue's gallery in the photo!! Does make you wonder what horrors are lurking in your nice shiny motor!!
A Bennett

Adrian

To answer your first post, yes, during my rebuild 11 years ago I also made up a unique length pushrod in the MC for the clutch. I converted the car from left hand drive and this involved transferring the pedal box assembly etc. I found that the push rod was just a smidge too short. It has always worked fine ever since, including conversion to the 5-speed box and MGB clutch.

Steve
Steve Gyles

Further to my last, my clutch pedal had to be changed on swap over to RHD. I recall looking at the new manufactured part and noting that there was a slight geometric difference in operating arm above the the pivot. Like Adrian I ran out of screw adjustment on the pushrod.

Every other part in the system was circuit was either brand new or reconditioned, so the need to manufacture a new push rod was entirely down to the difference bewteen the LHD clutch pedal and the new RHD pedal that was supplied to me.

Steve
Steve Gyles

Thanks for that Steve. My car was originally ex-US, and was converted to RHD. I can't detect any wear at the slave cylinder end, so it seems that the problem may be down to differences in the pedals - it sounds as though mine and yours were manufactured at about the same time. I shall however keep a wary eye on the pushrod adjustment from now on!! AB
A Bennett

This thread was discussed between 02/03/2008 and 05/03/2008

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