TR4/4A TR4A Intermittent rear wheel locking?

[trbby2]

After a year of driving my highly restored TR4A without an issue, it just started making a noise like something is loose in the right rear wheel area. It also seems to drag there intermittently, first making me think it was a flat tire. My first look found nothing out of the ordinary. My last test drive after resolving(?) a backfire issue resulted in what appeared to be the right wheel locking to the point of skidding the tire. Driving back to the garage was uneventful, but I won't leave the parking lot until finding out what's going on. It's raining now, but will lift it to inspect the wheel, brakes, and hand brake mechanism. Does any of this sound familiar, and are there suggestions as to where to focus my attention?

 

[mctriumph]

A spring loose or broken in the brake drum?? Lining failure?
Mad dog

 

[George_H]

Sounds like lining failure to me as well.

 

[trbby2]

You guys are awesome. Does the attached picture look like a lining failure? I think so! The left side is OK, but I'll probably replace both.

 

[CJD]

So...where are the rest of the rivets?

 

[trbby2]

There was no visible evidence of rivets. I see some scratch marks on the back of the brake pads, so maybe they came apart and all fell out. The brake drums are clean with no scars. Something was definitely wrong with those brake shoes.

 

[KVH]

You guys are awesome. Does the attached picture look like a lining failure? I think so! The left side is OK, but I'll probably replace both.

Amazing how quickly some of the folks here figure things out. So cool.

 

[mctriumph]

Probably replace both???You have just received an engraved invitation from the Gods of Good Luck!
You should also do everything else, like wheel cylinders /resurface the drums /check the U joints.
Just saying, when your Tr cries out for service, do it right.
Mad dog

 

[Sarastro]

Well said, MD.

I saw those holes, too, and wondered why the linings don't seem to show rivet holes. In any case, I haven't seen riveted linings in decades. If riveted, they must be really old.

 

[trbby2]

Yep, no rivets, just bonded, or at least they had been bonded once upon a time. The attached picture shows what is left of the bonding. I spoke to Moss Motors and they confirmed bonding, so I have a new set coming. Everything else looks good, although I'll tweak the parking brake a touch.

 

[CJD]

So, crappy parts strikes again!

 

[bammons]

Yes but a pleasant afternoon lovingly fixing/improving your baby. I thought that was the real reason we have these. Glad it is an easy fix that is something itself. Bruce

 

[CJD]

Your very pleasant personality is how the suppliers continue to provide sub-standard parts that have serious product liability concerns. Fortunately all is good with your failure, but it could have easily injured or worse if the situation were different. The suppliers take advantage of all of our pleasant personalities in the Triumph world.

 

[trbby2]

I got a new set of brakes from Moss, made in China and bonded without rivets, and they are installed. I struggled with the lower springs until I found a solution to keep them in place while wrestling with the shoes to get them in place. Note the pegs I put in the holes to keep the springs from popping off everytime I moved the shoes. I used a heavy walled plastic tube I had laying around that fit snugly. Once the manhandling and cussing was done, I just pulled them out and started the other side. It made it much easier.

 

[trbby2]

This is what happened next. The brakes are installed and adjusted, wheels fitted, and the car is back on the ground. NO BRAKES! The peddle goes to the floor. I had no leakage from the pistons while installing the brake shoes. I pumped the brake peddle repeatedly and checked the fluid level. I lifted the car again (floor lift under the differential) and looked at the brake adjustments. All good. I sat inside while the back end was up and the brake peddle was fine and all looked good. Hmmm... Back on the ground and again the brake peddle went to the floor. More Hmmm....The hand brake continued to work fine, but that's it. I lifted it again, sat in it and the brake peddle was now as it should be. So now what? Up good, down bad. Why? I don't know. I then sat in the car repeatedly stepping on the brake peddle and had a friend slowly lower the car so I could see where it stopped working properly. It continued to work as it should this time. Again, why? I circled the parking lot a few times and the brakes worked fine and felt maybe better than ever. I'm reluctant to go far until I have a lot more parking lot experience or if someone has a good explanation for why it could have acted this way. Any thoughts?

 

[mctriumph]

You did not mention bleeding the brakes or the age of the master cylinder. I am of the
opinion that every time you drive anywhere, you literally bet your life on your master cylinder.
Having had to repair HUNDREDS of cars(over the years) that were wrecked, I can say brakes caused
or contributed to a lot of them.
Do it right , do it once.
Mad dog

 

[trbby2]

I did not bleed the brakes, thinking that wasn't needed because there was no fluid leakage during the brake shoe installation and they worked when the rear tires were off the ground. I don't know the age of the master cylinder, but I'll look into that. It still doesn't explain why the brakes worked when the back end was up and not when down (twice) and then worked when down the third time. The only difference being that I sat in the car pumping the brakes while it was set back down. Still a head-scratcher.

 

[Sarastro]

There is a seal in the master cylinder that prevents the brake fluid from flowing back into the reservoir. It depends on fluid pressure to stay closed. When you installed the new shoes, you probably forced fluid back into the cylinder and that opened the seal, which might have been sticking a little. Then it took a few strokes and some time to reseal.

This might be a good time to rebuild the master cylinder. It's a simple job to replace all the internal parts. Rebleeding the brakes afterward is more of a job.

See the shop manual, p. 3-202.

I've never been comfortable with that design, as your life depends on one little piece of rubber. But that's what we have.

 

[CJD]

Pulling the hand brake, or pressing the cable can take up slack and make the brake pedal "feel" solid. Perhaps your jack is putting pressure on the handbrake cable??

All I can think is the MC rod is mis-adjusted. The MC must be able to return fully after you release the brake pedal. The last little bit of travel opens the hole which admits fresh fluid from the reservoir. If the piston does not return fully, it cannot pump back up.

 

[trbby2]

I think Sarastro was right. The master cylinder did seem to recover after a few days that had intermittent failures. I purchased a new MC from Moss and had it installed and bled with DOT4 fluid. The clutch fluid was clean and checked for moisture and left alone. Up and running again and heading towards a proper tuneup. Thanks to all of you for your advice.