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MG TD TF 1500 - Brake Help

I am experiencing a wierd problem with my TD's brakes. The front brake cylinders are holding a slight amount of pressure. It is causing the brake shoes to drag slightly. I can turn the front drums by hand with out excessive force but there is a difinite drag. The rear drums give a full release.

If I open a bleeder, the brakes go back to the full release position.

If I adjust the brakes on the front to be "free" without any drag, the drag reappears after the brake pedal is applied. The rear brakes function OK and give full release.

At first, I suspected the master cylinder but the rear brakes getting full release makes me think that it is OK.

Any ideas or experience you can share with me will be appreciated.

Bill Loubiere
52 TD
Bill Loubiere

Bill it sounds like you might have a problem with the brake shoe return springs. Make sure they are installed per the Shop Manual and are between the backing plate and the shoe. There are a couple of holes in the shoes to use for the springs and I always use those that are the farthest apart. Check the brake shoe steady springs for proper installation and tension. The shoes should be difficult to move around by hand.
Jim Merz

Bill, Jim might be right but I would look at the brake line hoses, probably collapsing internally & not letting fluid return. Only cure is replacement of hoses.There is also a small valve in the rear of the master cylinder but that will affect all wheels usually.
Gordon Wright

I agree with Gordon - replace your hoses. The rubber is collapsing and acting as a check valve preventing the fluid from returning completely.
Gene Gillam

Bill - Check that your wheel cylinders are installed correctly, since it is possible to install them upside down. Secondly, check that the shoes are installed the right way. This is a real easy thing to get in backward and when it is done so, they won't adjust properly (been there, done that). As I recall, the pictures in th shop manual will shoe which way the shoes should go, but you have to look at them carefully. Good luck - Dave
David DuBois

Another question-The shop manual indicates that the flex hose should go to the front cylinder. The ones on my car are installed on the rear cylinders on both wheels. I could swap the hardware on the front wheels and have the proper connections but the routing of the flex hose would be a mystery.

The hard pipe connection is on the back of the shock mounting area. It would seem that the flex hose would have to go through or very near the shock arms and might get caught. Can anyone tell me more about this mounting? How long should the flex hose be?

Thanks again for your help.

Bill
Bill Loubiere

The flex hoses screw into an adaptor bolt at the banjo (hole to wheel cyl, top opening to the steel hose that runs foreward )at the BACK cylinders. Not sure what you see or read in the manual, but it is incorrect. All above advice spot-on.
George Butz

Bill:

Been there, wondered that ! If your referencing the same workshop manual, Page M.6; figures m.5 & m.6, I too mistook the brake hose installation as going into the front cylinder. However, those illustrations are of the RIGHT front brake assy. Since the front suspension on the car is pretty symetrical, it can appear to resemble the left front wheel brake, which would cause the initial confusion. The hose does, as George correctly states, attach at the rear cylinders. On page M.7 it shows the LEFT front brake assembly with a bleeder hose attached. You will note that the brake hose is depicted as being behind the kingpin, thus attaching properly at the rear cylinder.

An installation note: When you replace the 3 hoses, screw them into the cylinders first (the tee on the differential for the rear hose), tighten, and then attached the other end to the frame flange. It won't work installing the hose at the flanges first. Also be sure to not install the hose with a twist. There are lines on the hose for visual reference. You should be able to see the lines run from connector to connector even as the hose bends while installing. Bending is OK, twisting is not.

Jim

P.S...A point to ponder: I've always wondered why they call where I live West Palm Beach......when it's actually on the east coast of Florida. Not only can't we count (votes), apparently we can't tell directions either !
Jim Rice

Jim,

Take a look at page M12 Section M12 "Replacement of the Wheel Cylinder". Under "Front" it says "must be fitted so that the flexible hose is connected to the front cylinder and the bleed screw to the rear cylinder". It also says the same thing in the Bentley manual.

I don't see how it can be done. I was wondering if others have them installed this way.

I don't think it has anything to do with my brake problem. I have been eleminating things one at a time but have not found the solution yet.

I checked the hose by bleeding upstream of the hose. The brake shoes returned to normal.

The problem started AFTER a cylinder rebuild. Prior to that the brakes worked fine to my knowledge. The car had been set up for engine replacement (thrown rod) and one of the cylinders froze. The brake wheel cylinders were honned from .875 to .885. Could the rubber get caught iin the gap?

I have not eleminated the springs yet. I am looking for a spec on them. They appear tight and I will order new ones shortly if I can't find any information. They are installed on the inside of the brake shoes on the holes requiring the most tension.

Thanks for all the suggestions.

Bill
Bill Loubiere

Bill:

Read the section you are referencing, and sure enough it does state to run the brake hose to the front cylinder. That paragraph is definately a typo. If you also read Section M.13 (the last paragraph) it makes a statement about the brake line union on the master cylinder side. While it may be a true statement, I have no idea what that has to do with the subject being discussed...Removal Of The Flexible Hose. The hose absolutely attaches at the rear cylinders. Cylinder installation should be so the front cylinder action pushes down on the brake shoe.

Puzzling as to why you have a return issue. If the springs are in the most distant holes that produce the most tension on the cylinder pistons, that downforce should be more than adequate to return the pistons to the fully closed position. If the springs are still tightly wound (no streched areas) they should be fine.

When you experience the problem, are both cylinders hanging up or just one? That may be an indication to examine one more closely. I don't thing the honing process would have a detrimental effect on the operation unless the honing was not done right. In that case it's possible the rubber piston cup might be hanging up on a rough surface.

Also, check to see which way the rubber piston cup is facing in the cylinders. It should be installed exactly as depicted in figure M.11. If for some reason it's backward, It might be possible that the lip of the rubber piston cup (now facing upward in the cylinder) is being caught in the gap between the cylinder and the piston.

You may also want to review the info on page M.4 which discusses the master cylinder. Since the wheel cylinders were rebuilt, it may have changed the dynamics for the master cylinder. Be sure you have adequate play in the pedal to allow the master cylinder return springs to return the master cylinder piston all the way. You may need to re-adjust the brake pedal linkage (pain in the ass). Also, don't overfill the master cylinder. If its too full, there is no place for the return fluid to go and might be causing the problem.

I'm out of ideas after that. Hope this info helped

Jim
Jim Rice

What is the condition of the Master cyl? The rears have only one cyl, the front two, point being that if the MC is sticking, a slight bit of pressure would put twice the force on the front shoes, hence your drag/residual pressure. Don't see how a wheel cyl. incorrectly assembled would work at all without leaking. bleeding the brakes forces the piston all the way down, scaping off scum/rust that use to be at the bottom of trave. Just a thought. "If I open a bleeder..." This just may indicate pressure remaining in the system, rather than lack of return. HAve seen several really nasty master cyls over the years that were not that old- full of sand, rust, gunk, etc.
George Butz

Thanks all for your suggestions. George hit it on the head. The master cylinder is the culprit. His analysis of why the front were hanging and not the rear appears true.

I appreciate all of the sugestions and help. It is great to have a source like this.

Bill Loubiere
Bill Loubiere

This thread was discussed between 07/09/2001 and 09/09/2001

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