MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - What type of clutch slave is this?

This was supposedly a standard 1275 1" slave several years ago when I bought it. I now find it needs a repair kit, but can't identify which kit is correct. This slave only has a rubber ring and the boot on the end, and no circlip inside. The ones I see from the usual suppliers have both a ring and a cup.

The cylinder was not actually leaking, but when I removed it to fit a remote bleed tube the seal seemed very loose to me. It is marked COUNTY S-139.

Les
L B Rose

There are basically two types of slave cylinder in circulation. Either may or may not have a circlip.
One that I prefer has a piston; seal; spreader and spring.
The other has a long piston, piggy back seal, and spring.
Alan
Alan Anstead

Ah, I think I understand why the seal kit from Sussex Classic Car has 3 rubber parts. It is to cater for both types of cylinder. Am I right?

I just realised I didn't upload the photos, so here they are.

Les





L B Rose

The piggy back seal like an O-ring side on usually is flat for its lead rising to a raised peak.
The large alternative for the piston; seal, spreader; spring variety looks overly large in the picture. They usually show 1" in the recess at the rear.
I usually assemble with some red rubber grease.
Alan

Alan Anstead

Thanks Alan, I have installed the slave with the new seal now. I also ordered a new pushrod, which has introduced another conundrum. It is much longer than the previous one, which was obviously not correct. I thought that the clutch release bearing (roller one from Ford Sierra) should have very slight play, or it would be always pressing on the release pad. But this slave has a spring inside. If I use the longer pushrod the spring is compressed, which makes some sense as that then allows more travel for the piston. However it will cause the release bearing to press on the pad, albeit lightly. Is this correct? Do you mean Alan that the spring is too long? This is the first time I have dismantled this slave so I am not sure it is correct.

Les
L B Rose

Both types of slave have a spring. In your case it actually sits on the inner end of the piston.
If the new piston rod is longer than the old, and the old one worked, just trim the new one to length.
Alan
Alan Anstead

The longer pushrod doesn't affect the actual amount of movement at the clutch itself. Despite the cylinder being around 2" long, the piston only moves over about 1/2", this distance being only dependant on the amount of fluid moved with one stroke of the foot pedal. Fitting a longer pushrod will move the position of the slave piston back up the bore which is helpful if its operating travel is getting too near to the open end of the cylinder and can sometimes compensate for wear in the various pivots etc.

I have never seen it written down, but suspect the two standard pushrod lengths relate to whether you use a coil spring cover or a diaphragm spring cover as they stand at different heights I think. But using other non standard configurations like different thrust bearings might necessitate it too.

I use a concentric slave on my 1275 and it runs in permanent light contact with the clutch cover. I worried about this at first but it is fine. Apparently there is much less stress by having the bearing constantly spinning at engine speed, than having it loose and changing from possibly near zero rpm up to 6000rpm pretty well instantly every time you press the clutch pedal to change gear! Anyway, mine has lasted well for around 70,000 miles since I made that conversion.
GuyW

Strangely I am now having trouble with the old pushrod as well. I suspect there is still air in the system. I jacked up the car on the offside and more air came out. I suppose I will have to keep at this until it works.

My roller bearing is not concentric so I am slightly nervous about it staying in contact with the pad. It is a diaphragm clutch.

Les
L B Rose

Les
If you are using one of my roller release bearing they can self centre.
If you fit a remote bleed, with a flexible hose, you can drill out the original pipe seat leaving just the thread in the slave boss and reduce the area available to the troublesome bubble.
Alan





Alan Anstead

Les, if you are using a Sierra roller bearing they are heavy, protrude too far forwards and are imbalanced. You would be much better off with one of Alan's.

Incidentally, when I said my clutch slave was a concentric one, I do mean the slave, - the hydraulic part is within the bellhousing and around the input shaft. All clutch release bearings are concentric. We'll, more or less, depending on how much wear there is in the release arm pivot bush.
GuyW

Guy, I knew what you meant, and probably you understood what I meant also! Obviously from my original post I was not talking about a concentric slave. I suppose what I really meant was that the roller bearing was not operating exactly axially.

Anyway, I made my own roller bearing carrier and very carefully ensured that it projected forward exactly the same amount as the carbon one. It has given no trouble in the last 5 years. One of the best upgrades I ever did, after many carbon bearings wore out rapidly.

My remote bleed tube is a bit of cunifer brake pipe. I used that because it was lying around, exactly the right length, and I already had the fittings and the flaring tool. I got yet more air out and the clutch action is back where it was before the latest master cylinder failure. I would prefer the bite point a bit higher, so may revisit the pushrod length at some stage. Or will that make no difference?

Les
L B Rose

Les, my apologies if you've already checked this, but have you looked at the clevis pin hole on the pedal or at the amount of slop or play in the pedal on its shaft?

After countless bleedings I couldn't make my clutch disengage fully. A new pedal shaft, bushes (spigot bearing bushes) and drilling out the clevis hole to take an oilite bush has stopped the clutch drag and given me a noticeably higher bite point than previously. Jeremy Mk III posted some good photos on the Clutch Dragging thread that I started:
https//mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&mode=thread&access=&subject=97&source=T&thread=202103291933309480
C Mee

Those are all excellent points. I have rebushed the pedal pin, and restored the pin to suit. I also welded up the clevis pin holes, redrilled them, and renewed the pins. Same for the slave pushrod. Have I missed anything?

Les
L B Rose

This thread was discussed between 10/05/2021 and 16/05/2021

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.