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MG TD TF 1500 - Brake cylinder failure - why?

As promised I'm starting a new thread. To recap, my LR brake slave cylinder has failed (I think?). It was rebuilt by myself about 2k miles ago as was the whole car using Moss rebuild kit. So far this is the only cylinder to fail that I know of. I've ordered a new after-market cylinder and shoes from Lbco.

So the nagging question in my mind is "what happened". The pictures below show that the rubber parts seem intact, which is good. The first picture shows what some have said looks more like axle grease than Dot 5 but where/how would axle grease have gotten there? The axle and bearing were totally clean when I pulled the brake drum! Did the cylinder actually fail or not? Whatever the stuff is, it ruined my new brake shoes!

Please tell me what you guys think happened so I don't ruin another set of brake shoes or kill myself!
Thanks much,
Ed


efh Haskell

Cylinder after removal and cleaning. All parts look good to me! Maybe my honing job wasn't done well? What happened???

efh Haskell

Hard to tell from the picture, the bore has to be mirror smooth, especially the area that the inner rubber seal rides on, especially with the silicone fluid. As cheap as new cylinders are now, I think it just better to replace. Just a thought- change or at least check the other cylinders too? George
George Butz

Ed - The rear brake cylinder are notoriously difficult to rebuild successfully due to the slot cut in them for the emergency brake lever (I destroyed a cylinder hone on one that I was trying to rebuild). The fact that the cylinder is aluminum doesn't help matters either. I think that what has happened in your case comes under the category of s--- happens.

In the process of replacing the rear axle in our TS this winter, I cleaned the interior of the two real wheel cylinders on out TD (I used a flap wheel to very lightly hone the interior of the cylinders). So far, there has not been any leak but then, I have only taken the car out for one short drive. I will be watching for any sign of leakage during the spring and summer. Cheers - Dave
David DuBois

I had that problem, except my rear cylinders were sleaved. But they started leaking in no time. Oddly enough I had a pair of very old cylinder rebuild kits my uncle had with the car. I mean very old, probably at least 35 years or so old. But they were still nice and supple. So what the heck, the new kits didn't work so I stuck the old kits in. No problems in 2 years now. The bores were smooth, no burs etc. It was just like the cups shrunk. I'm running dot 5. I was concerned with the old seals and compatibility with Dot 5 but they have proven better than the new seals.
L Rutt

Ed, its pretty hard to believe that this is brake fluid. Is your original picture rotated 90 deg.? I think the LH adjuster and piston would be pointing downward and therefore any brake fluid would be on the lower shoe. Your picture shows it is on the upper shoe. What is the cause of what appears to be metal dust on the adjuster? It almost looks like the rubber hand brake boot had grease in it that got pumped through to the outside of the cylinder when the handbrake was used.
Cheers, Hugh Pite
H.D. Pite

Doesn't the cylinder have a microscopically thin hardened surface in the bore? Honing would destroy that if it's true. Like George said, the bore has to be mirror smooth. PJ
Paul sr

PJ, there is not a thin hardened surface on these brake cylinders and the surface is not necessarily mirror smooth but could have a fine honed surface.
Hugh Pite
H.D. Pite

Ed,
I was waiting for this new thread to start to suggest that you get your existing shoes relined locally,,,, guess I'm a bit too late, sorry,,,
I got mine done locally,and didn't have to worry about shipping charges or core charge,,, and the guy even matched the new lining with a drum that I brought down,,, the price was a bit less than Moss also,,,,

SPW
STEVE WINCZE

Hugh, yes that photo is rotated. Here's a better one below. And, yes, the lower shoe is soaked with the stuff. I just checked the boot and it shows no sign of being packed with grease, nor would I ever have done so.
Steve, "locally", you've got to be kidding. I live at 9600' in the Rockies. I wish!
Could it be that Dot 5 mixed with road dirt = "grease"?

efh Haskell

ed, this is the only car i have run dot5 in so my experience is pretty limited..i did have an issue with one cylinder leaking..coincidentally a rear cylinder. mine was debris down in the bore where the line fitting threads into so the brake line could not seal. ...not your issue, but with that persistent leak i never saw the dust/road grime/ etc. make the material as it appears in your pic. my cylindr always looked "wetter" than your as well..yours does look like grease.
i did use a VERY small amount of antisieze on the brake shoe contact points on the backing plates and where the shoe engages the cylinder. regards, tom
tom peterson

I've been complaining about slave-cylinder rebuild kits for years...Not on TD's, but on many other cars....
The problem is that the kits use the original bore size for the seals....Common sense says that if you hone the cylinder, it is larger than the stock size....There is so much pressure there, that very little additional oversize
will result in a leak....
Basically, the only way it works, is if the cylinder is virtually perfect to begin with, and you are just cleaning it up with a hone...Beyond that , it is almost guaranteed to leak....
When I got "Rocky", the previous owner had done a pretty good job of rebuilding the rear slaves....They did not leak, until the car sat unused , during the body-off...
When I put it back together, they began to leak...
I purchased replacement slaves.
efh:
Are you absolutely positive that the residue that you saw
on your shoes, was brake fluid?
Edward
Edward Wesson 52TD

Edward, no, not sure, but there is no way to tell short of sending it out for chemical analysis?? A real mystery!
efh Haskell

I hadn't noticed the residue of what appears to be slightly magnetized metal filings in the first image until Hugh pointed it out. Since I have recently been working on the brake portion of my rebuild, I'm as concerned about the "filings" as I am the "grease". I'll be very interested to see what the final answer to this mystery is.
Kirk Trigg TD24953

A couple of thoughts how you might diagnose the residue.

Check whether the brake fluid you have used is flammable, some are some are not. The ones that are not only smoke and dont burn.

If you are fortunate you will have used a variety that doesnt burn and be able carry out this simple test.

Place the residue on a suitable surface and attempt to ignite it, if it is grease based it will certainly burn.

From your pictures I believe the residue is grease based all the leaking brake and clutch slave cylinders I have been exposed to over the years have never exhibited a build up of residue that had this appearance.

I think the contaminated brake linings are a separate issue

Graeme
G Evans

Are you in Crested Butte, CO ?????
STEVE WINCZE

Ed, Whatever happend, don't be too hard on yourself. Having had the TD in the family since I was 16 years old, I have lubricated brake shoes with 90wt, hub grease, DOT3 and DOT5 fluid. Loose rear brake drums, bad seals, inexperience, overpacking bearings, mysteriously failed rebuilds, a newly sleeved cylider failed, and other gremlins have ruined many shoes. It happens. Too bad the lining/rivet sets are not $25 any more. George
George Butz

Graeme: I just did your "fire" test. The greasy gunk indeed does burn but some clean Dot 5 does not burn. But if it's grease, where from? I did apply Lithium grease to inner hand brake cable at one time but 1) the cable looks dry now (on both sides of car) and 2) the rubber boot totally insulates the brake drum from the cable imo.

I'm also seeing that the grease on top of the cylinder (photo above) is different than the original "wetness" I first noticed that led to this adventure. That wetness was on the bottom of the backing plate's exterior surface. Attached is a new photo I just took of the bottom of the axle housing looking up. The backing plate is not shown but you can still see the wetness. There is a hex bolt at that location I never noticed! I have never touched that bolt but could it be the source of this wetness? What is it's purpose??

Any thoughts w/b appreciated!

Steve, yes, I'm in Crested Butte.
Ed




efh Haskell

I also submit here a new close up of my rear oil seal. Note that it is also "wet". Is that normal? Maybe this seal is just tired? I did NOT remove this seal, the bearing, or the half shaft during resto 2 years ago. (I don't remember why?) But would any grease in the bearing show itself here as "wetness".

Sorry about all this, hope you guys can follow it!
Ed


efh Haskell

I also just checked the axle breather hole. It is totally clean and open hence the common back pressure problem seems not a factor here. But there is definitely a liquid coming out from the bottom of the rear seal! The top of the seal is dry. If I rotate the axle I can now see this liquid very easily! I assume it's just differential fluid, correct? Maybe I just overfilled the diff a bit? Do I need to replace the seal? The archives are full of instructions for this except how to remove the split ring (without a special tool). Hum...
efh Haskell

The leak is between the split ring and what I assume is the rear seal.
efh Haskell

efh:
I'm more convinced than ever that what you have seen on the shoes, is not brake fluid...Good chance that it is grease that has been forced off of the axle and spun on to the shoes....
Have you tried cleaning the shoes with brake cleaner?
It's possible that the grease has not actually penetrated
the shoes...If it doesn't come off, you haven't lost anything...Brake cleaner is made to break down grease and oil, and leave no residue....I've seen grease and oil spills on porous garage floors, come right out , with brake cleaner.
Edward
Edward Wesson 52TD

Edward, I'll try the brake cleaner. Not much to loose.

What do you think about my rear seal picture above? Should I replace it? I don't have a slide hammer like WSM shows. Some have used brake drum as a hammer...hum?
efh Haskell

Looks suspiciously wet. SInce you are just a couple minutes of work away from removing the seal, change it anyway. Take a screwdriver and hammer, put the blade between the axle housing and the bearing/seal retainer on the corner at the bolt hole, and tap it in and outward. Go from corner to corner. Most likely the housing/seal will come right out, maybe with the axle. Good time to check the inner splines for twist now too. Make sure you clean the axle tube flange and bearing housing flange, and wipe with a thin film of blue permatex or something before reassembling. George
George Butz

Ed, is the oil seal collar smooth? It looks like there might be a little surface rust on it but it could just be the picture.
Richard Taylor TD3983

George, just ordered a new seal. Have been hammering on that area for an hour! I think some @#$@ DPO glued the 2 parts together or used red permatex or something. Somebody in archives (was it you?) said you can remove the seal without removing the brake plate support section. Just remove the split color first. Is that possible? I don't see how it could work?

I can't get the 2 pieces pried apart to see the whole collar! Still wacking away. Hope I don't break something.
Ed
efh Haskell

Just tried the old brake drum as a slide hammer trick and it worked great! The axle is on my bench and looks great to me. No bent or deformed splines or twists I can detect. Just gotta figure out how to separate the brake support plate from the bearing. It all came out as one assembly. Guess my HF cheapo puller might work?

Again, I apologize for this rambling, but it really helps the thought process!
Ed
efh Haskell

Ed - the split collar just pulls out, but you don't really need to remove it now. I agree that this is the time to pull the axle shaft and check the inboard end for twist. Unbolt the seal/bearing cap, tap it sideways, then carefully tap it off, using the ears. Or once it is unbolted you can leave it in place and use the drum as a slide hammer, which is what I do.

When you re-assemble, be SURE to wrap the splines of the axle shaft with masking tape, as they are sharp enough to cut into the seal when you install the new one.

Tom Lange
MGT Repair
t lange

Tom, thanks. We must have crossed in the mail. I got the half shaft out. Now how do I get the seal out? I tried my pullers from end of shaft to behind the brake plate but I don't have one long enough. Picture attached below:

efh Haskell

just tap on the seal plate Ed. It should come loose from the bearing with a little persuasion. Then tap out the seal and clean every thing up. Pay attention to the split collar where the seal rises on it. It must be mirror smooth. If not a new collar or a speedi sleeve might be in order. Your last series of photos looks like the issue was gear oil.
L E D LaVerne

Ed, sorry my trick failed, must have been glued on. Put the threaded end on a solid surface (workbench or something) and just tap around the edges and it will likely fall off. George
George Butz

Ed

It may be the angle of the picture, but the brake shoes in the first picture look to be very thin. If that is the case, I have to wonder why. Were they dragging and could you have gotten the cylinder hot enough to cause the failure?

I have had the same shoes on my TD for 15 years and while I don't drive it every day, it does get used frequently in the summer.

I am also of the belief that what looks like grease is just thickened axle oil.
Bruce Cunha

Bruce, I think it is the picture but will check when the new ones arrive.
One last question (I hope, but you know how that goes). My roller bearings are not packed with grease like the front wheels are. Is that correct? The WSM has no mention of packing them. If true, how do they get lubricated? Does gear oil just slop down the shaft from the differential or something? There was about a jigger of oil in the shaft when I pulled it yesterday which drained to the floor at that time. The shaft itself was just "damp" with oil. Is that how it's supposed to look? Doesn't seem like much lubrication??
Ed
efh Haskell

Ed, the bearings get lubed from the rear end oil. Once the differential starts spinning it will raise the level to push it down the axle ..along with cornering forces. If the level is correct in the rear end they get plenty of oil.
L E D LaVerne

Ed - the bearing is half held by the axle housing, and half held by the bearing/seal cover. You can tap off the cover without a problem; I put it into a very open vise so that the cover ears rest on the two jaws of the vice, then holding the shaft with one hand I use a rawhide mallet to tap the shaft (and bearing attached) out of the cover. If the bearing is bad you should need a strong press to replace it, or a machine shop.

Tom Lange
MGT REpair
t lange

Got it apart, thanks guys. Does the seal come out from the inboard or outboard side of it's plate?
efh Haskell

Doesn't matter, no ridge or stop if I remember correctly. George
George Butz

This thread was discussed between 04/04/2013 and 07/04/2013

MG TD TF 1500 index

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