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 MGB Technical - Folly to rebuild clutch master cyl?

I've got the clutch master out and on inspection the bore looks good. The outside looks like original equipment!
Is it folly to rebuild these, seeing how difficult it is to R+R, or should I just buy a new one?
Cleve Crews

If the bore is smooth, should work fine with a new rebuild kit. Take pictures of the piston as the picture in the rebuild kit is not an easy one to read.
Bruce TD4139 Cunha

Should be ok if the bore's ok BUT looking at the pic. on your other thread - I would suggest you have a real good look around the reservoir and check that the dreaded rust hasn't eaten into the reservoir too much------
A 3/8 drive socket and swivel usually gets that bottom bolt ok also the grease sounds like some type of graphite lube, it travels like nothing on earth, goes up your arm, in your shirt,in your hair,everywhere----but lubes well and is good for places like that, that seldom ever get relubed
willy
William Revit

"check that the dreaded rust hasn't eaten into the reservoir too much"

Had to replace one of mine as when bleeding with a gunson's fluid started going everywhere. The top had perforated, externally didn't look too bad but I presume moisture on the unprotected underside had eaten through. I was lucky to get original NOS tin replacements at spares fairs for the ones I have had to change, hopefully will be able to again soon from the usual suspects.
Paul Hunt

Looking at some images on the web, I've decided my gray goo on the master may be deteriated boot. As you can see in the pic, there is no boot and some of the boots in the pics i found were the same color of gray.
Think that's possible?



Cleve Crews

If it's an original Lockheed item, the part numbers are on the seals themselves. Have a close look and make sure you get the right parts, matching up to these numbers. If the bore is sound should be no problem.
NorthWest Automotive Hydraulics in the UK can supply you with the right, high quality, parts.
Allan Reeling

I just lightly honed it out a bit to check the condition. There are light pits in the bottom. Not sure I want to put this one back in the car.
Cleve Crews

Not sure what it's like in the US, but the ones the usual suspects sell here now have thimble sized reservoirs that make bleeding a proper chore. Plus they look daft.

Just looking at external condition alone, I probably wouldn't do that master, but try and get a proper tin one rather than the very latest ones if you do replace it.
Roadwarrior

Cleve,
Stainless sleeves are available fitted at a reasonable cost over here. Someone must do it in Alabama. The only problem with that is lead time, I suppose.
Allan Reeling

"...as when bleeding with a Gunson's fluid started going everywhere. The top had perforated..."

I had the same problem with my brake master. I had a jet of fluid which landed on the front wing!
Dave O'Neill 2

I tried to get a pic of the pits, but it's a little difficult. The pointer is pointed at the two spots, which of course are on the bottom.
A new original spec cyl is available locally for $139 usd. Another version with the small reservoir cost $49 usd.


Cleve Crews

Cleve,

That looks pretty rough to me. You could try honing it a whole lot until they disappear. That may oversize it, but my experience is that over honed and smooth has a better chance of sealing than pitted.

Charley
C R Huff

Throw it away - it's gone
William Revit

Okay. A new one it is and I think I'll go with the original type even though it's almost 3 times the price of the plastic reservoir model.

Spring is finally here and I want to enjoy the 78 and 79 before summer arrives and it gets HOT!


Cleve Crews

Yep. That looks way too scored. Could hone out, but new or a sleeve is probably in order.

You are probably right on the money on the goo. Probably original and someone used the wrong brake fluid. It will turn the old British rubber into a gooey mess in a matter of hours.
Bruce TD4139 Cunha

With cars that look that good I think the original well worth the outlay. You maintain the standard.

Regards
Roger
R Taylor

Cleve: you made the right choice. These cars are pushing 40 years old.there is only so much one can overhaul. Time is not our friend when it comes to these cars.

I am generally an optimist, but when it comes to safety and reliability, I choose not to risk it. Besides, how many times do you want to do the same job over??

Cheers
Gary
79 MGB
gary hansen

Got the new factory part Friday and I'm going to install it today. Wish me luck!


Cleve Crews

OMG!
What should have been a 30 minute job turned into 40 minutes because I couldn't get the bottom bolt lined up with the captive nut. As my Scottish mother would say, "what a pain in the ar*e"!
Is there anything worse to work with on a B?


Cleve Crews

All back in working order. New slave, master and hose.


Cleve Crews

Well done - now go drive and enjoy it
willy
William Revit

This is the 4th slave I have replaced in the last few months, on four different Bs. All have gone bad due to age. I'm getting pretty good at bleeding the clutch, with the help of my wife. She got mad today because I told her not to adjust the mirrors and seat, just to sit in the car and push the clutch pedal when I say so. She told me not to be so bossy. I looked over and she was pumping the brake pedal!


Cleve Crews

If that's lunch in the pic-----well I'm not hungry

Tell your lady not to feel too bad for pushing the wrong pedal-----I took a MGB in for rego inspection once and the guy reckoned the brake pedal went straight to the floor--yep, it was the clutch pedal he was on.
willy
William Revit

could that gunge be the result of mixing silicone and glycol fluids?

"Is there anything worse to work with on a B?"

Oh goodness me ... roadster windscreen? GT front and rear screen trim? Heater? Gearbox crossmember mounts?
Paul Hunt

William,
She doesn't stay mad long. A steak dinner fixed her to like new.
Dolores had a TR6 when I met her, so for years I would tell her that's why I married her. Any woman that can man handle a stiff TR6 clutch pedal is the woman for me.


Cleve Crews

Paul Hunt,
You're right about the GT screen trim!
About the roadster screen. Is it a pain to remove and replace complete screen, or are you talking about replacing the glass in the frame? I've never done either.
Cleve Crews

Cleve,

Sorry I picked up on your thread so late, but perhaps this tip will assist on your (and anyone else's) next folly with the bottom bolt/s in the pedal box. After replacing three brake master cylinders on my midget a few years back (thanks Lockheed) I thought their had to be a better way.

The attached photo is a metal coat hanger that I fashioned to capture and hold the bottom bolt, and allowed me to feed it into place with minimum effort. Once in place with the nut and washer fixed you simply twist the wire to release the bolt head, and thats it.

Larry C. '69 Midget & '74 B/GT




Larry C '69 Midget

I conclude you are a man who has made some VERY good decisions in your life Cleve.

Well done.

Regards
Roger
R Taylor

Larry,
The coat hanger suggestion is good!
My problem was not holding the bolt, but getting it aligned with the hole in the MC and the captive nut on the pedal box. If the MC is not perfectly lined up, the bolt will cross thread, or not go in at all. I put a tapered drift in the MC hole and the captive nut hole and tightened the top bolt. This didn't work, so I undid the top and used a long screwdriver to position the MC until the bolt went right in. Lots of prayers in between! Once it was started, I went back in the cockpit and with an extension tightened it up. The torque of the metal line is what twisted the MC and made it hard to align. I put on first so I wouldn't cross thread the fittings. Maybe next time I'll put it on last.

I also found my clutch disk to be stuck to the flywheel, which made engaging a gear impossible. Pushing the car back and forth while Dolores held the clutch in and 3rd gear, broke that free. Close call!
A result of the car sitting since 1992.

The 66 needs a slave and maybe MC next.


Cleve Crews

"Is it a pain to remove and replace complete screen, or are you talking about replacing the glass in the frame?"

Removing and replacing the screen without replacing the lower seal should be relatively easy, I did it single-handedly (on my own, not with just one hand!) The problems came when replacing the glass - getting the frame back together again, and again when the whole thing back in the body with a new lower seal - both three-handed jobs. But then someone recently said they got their frame back together quite easily. So really you will only know when you come to do it :o)
Paul Hunt

Paul,
I was referring to putting the whole frame back on the car. I need to replace the bottom seal on 5 B's. Dread it!
Cleve Crews

Cleve,

For the master cylinder/s (brake or clutch) on my midget, and B/GT their is/were no captive nut/s on the pedal box or master cylinder/s. Not that I needed one, but this was a very high level of frustration.

Oh, and good luck with the windscreens.

Regards,

Larry C.
Larry C '69 Midget

Larry,
On my 79 there is a captive nut on the bottom of the clutch MC box and a bolt and nut for the top. With yours not being the same, I can see where the coat hanger comes in handy.
Btw, I almost bought a 74.5 BGT in Delaware while working there a few years ago. I was going to buy it and drive it home, but the wife said no.
Cleve Crews

"I was referring to putting the whole frame back on the car"

I did mean the whole thing when I said "Removing and replacing the screen without replacing the lower seal", referring later to the glass.

I'm pretty sure neither had captive or welded nuts on my V8, where I've replaced both masters. I 'stuck' the nut and washer to a spanner while I carefully got the bolt started. Took a couple of goes.
Paul Hunt

My early cars don't have captive, or welded nuts, on the MC box. They are like the top fitting in both locations with with just a nut and bolt. I guess the factory thought they were doing us all a favor by changing the bottom fitting.
What year is you V8? My 74 back cars just have the holes with no captive nut.
Cleve Crews

The bottom bolt is easy if you firstly fit the nut and bolt without the master cylinder. The trick is to put some superglue on the face of the nut then run the set screw through bolting the nut to the bracket. Leave it a few minutes then remove the setscrew. Now fit the master cylinder easily as the lower nut is now captive with the superglue
Iain MacKintosh

The captive nuts came with the dual line, inline servo cars (late rubber bumpers in the UK).

The earlier pedal boxes can be done with a bit of masking tape and a good pair of crank handle type ring spanners. Just put the setscrew/bolt into one ring spanner, masking tape the head in, then guide it around the cylinder into the lower hole from back to front. You should be able to reach around the front and place on the spring washer and nut easily. Leave the lower loose when it's almost nipped up, and fit the top one. Then tighten them both. Is this what you meant Paul?

The later boxes need some small hands or clever use of sockets, UJs, extensions etc for the captive nuts.

The later Midget/Sprite pedal boxes are much more horrific than the MGB ones, but the above trick can still work.

As far as tourer windscreens go, the bottom seal can be a dog for many reasons. It's hard to slide into the lower frame to start with, needs the ends fiddling with to allow you to get the screws in that hold the side peices to the bottom, and then can curve under on installation meaning you have to hook it out with great care. Plus the new ones need a lot of 'bedding in' meaning it can take some downforce to get the screen to body screws in and even more tugging to align the screen to the 1/4 lights.
There are at least 2 types of lower seal floating about on the market these days. The one the usual suspects seem to sell has a slightly ovalled T profile on the part that engages the lower seal runner on the frame. There is another one (sorry don't have any vendors to hand) which has a much more correct T profile and slides in with probably 30% the effort of the other one. I'll have a look and see if I can find the name of the people who do this seal. It might save someone a lot of effort (and swearing!)
Roadwarrior

Clive - 75, but UK cars didn't get dual line brakes and the very different master cylinder arrangement until the 77 model year.

Roadwarrior - probably, it's from memory quite a few years ago now.
Paul Hunt

I came up with the same solution as Iain. Glued the nut to the cylinder.
Bruce TD4139 Cunha

This thread was discussed between 26/03/2015 and 05/04/2015

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.