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 TD TF 1500 - Brake woes continue

Having had issues with rear brake drum overheating and having to strip and clean the rear brake cylinders on both sides because they were seized, I found that I still having braking problems. All brakes were dragging and I seemed to lose pedal movement - in 1/2" it just went solid. Not enough push-rod clearance I thought so attempted to adjust that and no joy. Consequently everything had to come off including the master cylinder (horrible job on RHD because of obstruction by the exhaust, and the 5spd gearbox mountings). I found that there was no more adjustment left, so ground about 1/8" off the end of the pushrod in a desperate attempt to improve things. Put it all back together and I find its made not one jot of difference. The master cylinder is a replacement from TRW that I fitted a couple of years ago. Never taken it apart, but can't think of anything else causing this as it doesn't seem to be releasing pressure when pedal released. Comments welcomed.
Dave H
Dave Hill

Dave search the Archives for "locked brakes". Here's one that I think hits the nail on the head:

http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=201607061848004179

The brake master cylinder piston seal is swollen(heat/fluid type), contamination possibly in the master cylinder blocking return hole?

Note Butch Taras modification of the piston to allow extra clearance inside master cylinder relief hole.

Richard Cameron

Yes that does seem to be exactly as I have experienced. I am also using Dot 5. Looks like I will need to remove the master cylinder agsin and investigate. Thanks
Dave H
Dave Hill

I had the same problem. After removing the MC a half dozen times along with the drums to inspect the shoes, wheel cylinders, return spring, backing plate orientations etc. it finally ended up being the MC valve. Replaced it and used a new Lockheed overhaul kit and I haven't experienced any other brake issues as of this writing

Bill Chasser
TD 4834
W A Chasser

Dave,

You might like to look at the MGAguru on dragging brakes. I know it is a different system, but an area of commonality is that many problems seem to go back to modern aftermarket master cylinders and associated kits.

Good luck, and please keep us informed.

Kind regards,
Michael
M R Calvert

Yes thanks, have read that now and lots of good info. I have decided to dismantle the TRW cylinder and see if I need to replace anything (not sure if spares are available) or shorten the piston by 10thou, as suggested by Butch Taras. Failing that I will get the original cylinder sleeved in stainless and rebuilt, seeing as there are numerous comments about issues with aftermarket cylinders.
Dave H
Dave Hill

Have now dismantled and reassembled the TRW master cylinder and this is what I found. The tiny bypass port may have been partially blocked. Hard to say for sure as fluid tends to prevent light coming through, but it certainly seemed much clearer when I put a pin through it. Some metal abrasion on the back end of the piston just in front of the secondary seal. Couldn't see any matching abrasion in the bore so could have been there from manufacturing, The hole in the piston for the piston rod had a small piece of paper scrunched up into the very end of it. Certainly not put there by me as I bought the master cylinder new and just fitted it, and it wasn't from my cleaning rags either.
Just in case those things had nothing to do with the problems I've had, I removed 10thou from the piston face (to make sure the secondary seal clears the bypass port). I would have done it on the lathe, but couldn't fully dismantle the piston assembly and remove the seals. There is an entrapped circlip at the end that must be removed and I couldn't. So instead I taped it up to keep dirt out then ground back the end and finished it off with an oilstone by hand. Took some time but I removed exactly 10thou after measuring and retaping several times. Then cleaned up with methylated spirits, lubed with Dot5 and reassembled. Next job is to put it back in the car and test.
Dave H
Dave Hill


Dave, Please let us know how it tests after you put the car back together and on the road. One other thing to confirm if you haven't already installed the master cylinder. Check that your pedal assembly is lubricated at the pivot to confirm there's no binding or stiff operation.
Richard Cameron

Dave

You are probably aware, however ensure you prime the master cylinder prior to installation, makes life easier to bleed the system.

Graeme
G Evans

I am puzzled as to how a master cylinder problem would affect just the one drum.

Matthew.
M Magilton

Matthew

I am also intrigued.

Maybe a function of how each brake was adjusted, initial post indicated all wheel brakes were dragging.Brake that was adjusted with the least clearance would be worse effected.

Graeme
G Evans

Yes, the pedal assemblyi is ok - it was all renewed when I converted the car to RHD, and I drilled and fitted the shaft with a grease point as well. I didn't prefill the master cylinder with brake fluid before fitting, desirable though that is, because I didn't want a facefull of silicone whilst fitting it (like last time). Access is a bit tricky and its all too easy to push the piston with the piston rod whilst doing it. It takes some manoeuvering to get in position if the fork is prefitted on the pedal (and its very difficult to remove and put back).
However, I filled it and bled it one time around last night and the pedal wasn't returning, so I left it to settle until this morning and will try again soon.
I think the one drum brake seized because in addition there was a problem with the brake cylinder on that wheel.
Dave H
Dave Hill

The brakes appear to function normally, 1/2" pedal clearance, then piston moves and resistance felt, locking the brakes. Release pedal and it does not follow my foot back up. Hook it back up and the brakes release. Weird. Plenty of spring pressure when reassembling and refitting the large circlip in the end, and the return spring is attached to the pedal. Something wrong internally with the mastercylinder I assume. I was very careful to reassemble everything back in the order I found it, but who knows. Rather than mess about with it more I took my original mastercylinder to Pastparts at Bury St Edmunds for rebuilding with a new stainless cylinder liner. They gave me a tour around the place to see how they do it. They also rebuild brake servos and disc calipers. Nice people who seem to want to do a good job for you and rebuild masses of these things. They got the stainless steel relining technology from Australia.
Dave H
Dave Hill

There is a company in Lismore NSW, Australia called Halray Brake Reconditioning. They put stainless steel sleeves in my master cylinder and all wheel cylinders a couple of years ago.

I have read somewhere of the term "the Halray System", (I think on MGAguru). I believe they also do some work RAAF aircraft. I spoke to them on the phone a couple of times and found them to be very good to deal with, and at the time also reasonably priced. (No personal connection).

It is possible that it is their technology that is being referred to.

Michael
M R Calvert

I just had a look at the invoice from Halray. It says "Sleeving in stainless steel is our core business".

Michael
M R Calvert

A bit more research - a look at the website for Halray shows that they developed and patented equipment to do this sort of work which they now manufacture and export, along with their sleeves, to a number of countries including South Africa, USA, UK and Canada.

I had no idea I was dealing with a company with that level of expertise. It is interesting where a reference in a post can lead one to.

Michael
M R Calvert

Pastparts in the UK employ about 12 people and rebuild hundreds of units per month so its a thriving business. Just about any make is catered for,
Dave H
Dave Hill

Dave,

Just looking back at your post about Pastparts giving you a tour around their premises reminded me of getting the same treatment from Crankshaft Rebuilders Pty Ltd in Melbourne. They make new cranks as well as doing other automotive engineering work. (They made mine for me).

Ian Shugg gave me and my wife an unhurried tour of their workshops which I found very interesting and greatly appreciated.

Ian is a serious MG enthusiast; he and a few mates took a container loaded with several MGs to the UK a few years back to do some touring and club days.

All part of the things that come along when restoring an old MG!

Kind regards,
Michael
M R Calvert

This thread was discussed between 12/06/2017 and 16/06/2017

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.