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MG TD TF 1500 - TD-4834 Brakes ...again!!!!

I'm back to disliking my TD again. I am having a problem with the brakes king up and no peddle again. My 90 mi trip last weekend Canyon carving went without a hitch and thought I was done with this. Today I take a 20 mi jaunt and it's doing it again. The MC is put together correctly and I had a +1/2 if free peddle at the beginning of the drive. They started dragging so I pulled over to the side. I then took the hand brake and pulled it up tight and released it. That was the wrong thing to do. It was locked up so tight I couldn't move it. Let it set for a half hour and was able to move it but the brakes were still dragging lightly and no free peddle to be had. I limped it 6 mi back to the house. The brakes only have 300mi and everything has been replaced. The MC has been apart on three occasions. Shoes, springs, wheel cylinders, hard and soft lines have all been replaced.

Question. Has anyone had problems with the Moss supplied rubber brake lines? I'm running DOT 5. I can only surmise that it is the rubber lines but really less than a year old and only 300mi. I'm mean c'mon!

Bill Chasser
TD-4834
W. A. Chasser

Sounds as if you might still need more free play to allow the fluid to return. Something similar happened to a friend and we simply gave it more free play and the problem went away.

Mark
Mark Strang

I've had Moss rubber lines with DOT 5 fluid on my TD for over 2-1/2 years and nearly 3,000 miles without any problem. I'd be surprised if they are the source of your problem. Good luck sorting it out.
Joe
Joe Olson

The free play does sound low. I'd try an inch, for a start - if the brakes are otherwise in good condition, you won't get too much pedal travel at full brake effort.

I know half an inch is the book figure, but it does sound as though the fluid isn't returning from the wheel cylinders.

David
DavePro

Try to replicate the problem, if you then open a bleed screw to relieve pressure and the brakes free off then you have one of two problems. The piston is not uncovering the recuperation hole (very tiny see WSM) or it is blocked. In some repair kits the cup is slightly long and covers this hole.
If you take the lid off the cyl and pump the pedal you should see a spurt of fluid as you release the pedal. The system is designed to hold residual pressure to inflate the seals and the spurt is equalisation.
Ray TF 2884
Ray Lee

Bill, Only a thought but, were the drums hard to get over the new shoes when fully retracted? Sounds like the dragging shoes are causing a heat problem and expanding the fluids in the wheel cylinders just enough to create this scenario. I have silicone fluid in the TF and have no problems. I could be wrong but I think Ray could be right and the pistons aren't retracting enough. PJ
Paul Jennings

I use silicone fluid as well and agree with all those comments. The brake shoes need to be a couple of notches off dragging, especially when new.
Dave Hill

Paul,
the recuperation hole is there to account for any expansion of the fluid. The system is pressurised from the slave cylinders to the foot valve, from the foot valve to the reservoir is atmospheric. If the fluid expands it forces the foot valve open and spills back to the reservoir.
Ray
Ray Lee

A bad brake hose would only cause either one front or both rears to drag, only happens with ancient swollen rubber ones, about zero percent chance that is the problem. Why was the MC rebuilt 3 times?? With all of the mis-matched and incorrect rebuild kits, no way I would consider rebuilding even once. Buy a new one, or send to White Post and have it rebuilt. If the MC piston is fully retracted and home against the circlip(via the spring) when you set pedal clearance, there is no way that the clearance could decrease or change, unless you have a mechanical problem in the pedal box (pedal loose on the shaft/something cracked, etc). If the MC piston is sticking part way down (as was the issue with some of the rebuild kits being too tight) and you set pedal clearance with it part way down, then if it popped back and returned to seat at the circlip, that would eliminate pedal clearance and perhaps cause your problem. Suggestion: these are single brake circuit cars. Don't try to save a buck as you could end up in a very expensive or worse crash. Also have heard of some of the bonded linings peeling loose, check for that too. But I bet it is the MC. George
George Butz

I have all the shoes backed off 1 click from hitting the drums. The wheels spin freely with no drag. Perhaps I should back them off another click. That would allow more travel of the piston and perhaps a better return. But it still doesn't explain why last week they worked flawlessly while putting the car through its paces while hard braking on 45 miles of intense driving. But I'm leaning toward the check valve in the bore being the issue. I have a newly rebuilt and sleeved MC that came with dads TD/c. I think I will install it today and see if there is any change in performance. I will follow up with my findings. Thanks for the input one and all.

Bill Chasser
TD/4834
W. A. Chasser

I think Ray Lee's comments are spot on and I would go there first.

I run Dot 5 in my car and have not changed the hoses in a decade. I also only have 1/2" travel and set them to 1 click too. I am pretty light on the brakes and they rarely get hot. Never had them fade or lock up.

Did you bed them and/or turn the drums? After checking the bleeding hole, that could be next.
Christopher Couper

If you have some wear on the peddle shaft then maybe the freeplay is due more to the wear, making things too tight?

Matthew.
M Magilton

Thank you all for your input. I replaced the MC and took the car out again. Unfortunately a cold engine sneezed as I left meeting with friends for coffee and and simultaneously blew out the front freeze plug. I didn't expect this as I had Tom Lange's brass plugs in place. I think when the engine sneezed it lifted the head and caused hot gases to enter the coolant system blowing out the plug. More work to do. Eventually the car will be reliable though it seems more sorting out is in order

Bill Chasser
TD-4834
W. A. Chasser

Bill - Ouch - That's a first for me!

Send me your address off-line and I'll be happy to send you a free replacement core plug. I stand behind everything I sell 100%

Tim Lange
MGT Repair
t lange

This thread was discussed between 04/12/2016 and 06/12/2016

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