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MG TD TF 1500 - sticky front brakes

Gents I have/ had a couple of problems with my brakes.

Coming out of winter storage I lost fluid and ended with low levels in the master cylinder as a result of a leak in the rear. Lots of air in the system and soft peddle. I have this disconnected and the cylinder is held closed by some cable ties to allow me to test the rest The brakes are bleed and the peddle is now firm.

Yes there was crud and what looked like small droplets of water floating on the fluid in the MC ( I should have replaced it last year when I bought the car...) I have flushed through about half a pint or more of fluid. Looks 'reasonably' clear on the way out.

The other rear brake actuates and releases fine.

The front brakes on both sides atuate but won't release.

If I adjust the pads away so that they don't rub then apply the brakes they will work - but not release and they bind up tight. Even if I back off the adjuster all the way this happens again once peddle is pressed.

I have driven the car in the local car park ( just across the road. I reckoned a little use and heat would help. They definitely work but are still dragging.

The brakes remain locked if I open a bleed valve. (Thought it migh be residual pressure in the MC). Bleeding doesn't seem to make any difference.

The rubber hoses look very good. Not likely that both sides would be collapsing to retain pressure ?

I am reluctant to start stripping the front hubs... Don't have the pullers etc anyway...

Before I order the parts what is your advice ? Is there a way to eliminate the Master Cylinder or the wheel cylinders from the equation short of working my way through a load of spares... :-)
Dave Moore

...Usually the hoses.... they collapse inside and make a one way valve... If all brakes stuck on, it might be the little relief valve hole in the MC, but if only one or two, usually the hoses... you might have the front cylinders freezing up....but pull the hoses.

You do have to (or should) bleed all the lines at the same time....
gblawson(gordon- TD27667)

More likely you have formed some corrosion in the wheel cylinders. If there was any moisture in the fluid, you will get rust or aluminum oxidation in the cylinders. I had this happen to my TD every year after winter storage.

You are most likely going to have to take the cylinders apart and minimally run a hone through them. flush the brake system with alcohol, dry it out and then fill with silicon. This has totally stopped all my brake issues for over 20 years.


In my case, I rebuilt everything, that may be the best thought for the long run.
Bruce Cunha

Gordon - if it is the interior of the hoses then if I disconnect one then the pressure will release and the cylinder will return to rest - yes ?

I'll give it a go now..

:-)

Dave
Dave Moore

No joy. Removed a hose. Wheel still locked. This also rules out the master cylinder retaining pressure I guess.

Must be sticky wheel cyliders and I will have to go with Bruces next steps.

Now I need to get special puller for the hub and a set of new seals at a minimum for the front.

Since I will now have to take most of the system apart I might as well do the whole lot and swap to silicone

Bum. Really wanted to spend more time on the road and less time on my back :-) Weather is great..not often you can say that in Ireland

Dave
1955 MG TF
Dave Moore

Hi Dave. It would be worth trying the remove the hub without a puller, both of my rear hubs and one of the front came off by pulling and wiggling by hand. The fourth I removed using an ordinary three leg puller and some metal bars fixed between the wheel studs. Matt
Matt Davis

....back off the brakes all the way....might work?
gblawson(gordon- TD27667)

Dave,

You can easily check if the problem is rusted pistons or a collapsed flexible hose. You don’t need to remove the brake drum. Just remove the wheel on the side which is blocking, (or both sides if you don’t know which is blocking) slacken off both the adjusters all the way, press the brake pedal down hard,
try turning the drum, it should be locked. Now loosen the bleed screw to let some fluid out, if, after doing this, the drum is still locked it is the pistons, if it is free it is the flexible hose.

John


J Scragg

Good advice there from John.
Almost certainly the slave pistons which will have black gunge seizing them. They can be tricky to get out, but controlled use of pedal pressure will help, controlled with clamps set loose to stop the pistons becoming garage missiles. Here is a pic of how I do mine, I also drape a rag over the lot in case of a brake fluid geyser.

Matthew.


Matthew Magilton


John - the result of the test you suggest says 'stuck cylinders'

Matthew - thanks for the pic with the clamps in position - definitely something to keep in mind. I shot the rear piston out by stamping on the peddle.

Actually broke the cheap light clamp I had on it. Replaced this with cable ties and works better. Holds them in but with a little bit of give.

Thanks guys for your suggestions.

Here is hoping that the bores of the cylinders are recoverable and a polish and new seals does the trick :-)


Dave
Dave Moore

A bit of work, (Nice afternoon project), but you will find the satisfaction you get well worth it. You should be able to check brake issues off your list for many years.

It will give you the chance to inspect and repack your wheel bearings
Bruce Cunha

This thread was discussed between 10/04/2011 and 12/04/2011

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