Rear Drum Heating Up

So I just need some reassurance/guidance. I replaced the rear shoes, cylinders, etc on my 99 XJ yesterday and it stops again (yeah!). However, two problems seem to exist now. First is that the Brake light on the dash still hasn't gone out (cylinder was leaking bad and I guess that caused the light to come on). Now, I can live with the light but I'm worried that it is still on for a reason.

Secondly, and possibly more worriesome/related is that one of the drums is hot. We are talking exhaust pipe hot after driving it on the highway. The drum on the other side is fine. It was evident that the pads were rubbing a bit when I put the drum on the hot side (driver's side), but is this normal? Is there an expected break-in period? I've only put about 45 miles on it since doing the repair, maybe it just needs some time? Could it be that the parking brake isn't fully disengaged?

Thanks as always,
S

Drum brakes are supposed to have a *little* drag but they shouldn't get wicked hot just from driving around. You most likely need to adjust the new shoes in a bit and decrease the amount of drag. This is especially true if one side is hotter than the other.
Yes, also, it could be the parking brake tugging them on enough to cause your issue. Check it out some more. But I would start by hauling the shoes in via the adjuster star wheel (screwdriver through the access hole). Pull them in a ways and then repeatedly drive in revers + full stop. If your self-adjusters are working properly they should dial in the shoes pretty well. Regardless, the key is just patiently adjusting the drums to get it right. It won't happen the first time... just keep at it for a while.



There was a horror story (I think with the XJ Giveaway vehicle) of the Ebrake sticking and generating enough heat to fuse the wheel bearing or something.

When I put the shoes on, I had to adjust the star thingy all the way in just to get the drum on.

On that horror story, was that right away or with continually driving? Only reason I ask is that I need to get it home tonight :twak:

Wonder if adjusting the parking brake might help....

S

You will also warp the drum and glaze your new brake shoe from heat. Something isn't right on the hot side. (Big news, huh.) Every time I put brakes together, the star wheel had to be adjusted out some after reassembly. If not, the parking brake is stuck on or maladjusted or something else is not assembled right. I would pop off both the drums and look to see if you did anything different between the two sides. The drum is supposed to only drag very slightly. With it apart, you can see whether the parking brake lever is fully released.

while you have the drums appart put some high temp grease in the (non)selfadjusters

Mine just did the same thing. Its the emergency brake cable, froze up not allowing the shoes to retract fully. Removed the link between shoes and no more problems. Mines a auto and I never use the emergency brake.

probably a frozen ebrake cable did you check and make sure the ebrake works the brake light on your dash is for the ebrake i would check that they tend to get stuck and will cause the brakes to drag on the drums more then they should causing the heat problem

You may also have a defective wheel cylinder which is stuck or otherwise not retracting fully.

First off, thanks for the responses!

So a quick update. I messed with the tension on the e-brake and it seemed to make no difference. I changed the shoes and springs again on that side to no avail (although the fit with the new set was a bit better). So I'm going to go get the drum turned in a little while to make sure it's not warped.

The idea of a sticking cylinder is possible. I noticed yesterday when I was replacing the shoes (again) that I needed to press the ends in a bit to get the pads to fit right....hmmmm should the cylinder have any compression left in it if the brakes are not being applied?

S

Another update:
Turned the drum = no improvement
Replaced the wheel cylinder (again) = maybe improvement

That side still seems a bit hotter than the other, but not the "raging fires of hell" hot that it was getting before.

Brake light is still on. Disconnected the battery hoping for a reset, annnnnnd nothing. Any ideas on the brake light?

The Parking brake seems to be functioning normally. Does anyone know if there is a fill level float thingy in the brake fluid resevoir?

S

p.s. last time I buy important parts at Autozone, this is the third time a new part from there didn't work.

i absolutely hate doing drum brakes. the springs and retaining pins are a complete pain. plus it has to be put back together the right way- hey, speaking of that compare how the pass side is put together to the drivers. if you need, have someone take a pic of properly functioning drums.

or you could just go to rear disks and have it that much easier.

the brake light is telling you that the ebrake is engaged soemthing isnt right with your ebrake

two things control the brake lamp on the dash. The first is the parking brake (as stated before)-- if the switch in the handle malfunctions, you can get a steady light regardless of handle position. The second trigger for the lamp is a pressure differential switch in the brake proportioning valve (distribution block below the master cylinder). It senses the pressure in the front brake lines and the rear brake line and grounds the circuit if one half is significantly greater than the other. Essentially, inside the block is a "free floating" contact that will move forward or rearward when pushed by a higher pressure on one side of it versus the other side. If the switch has been pushed to one side or the other for a while, it can stick in that position and fail to return to the center when equal pressure is renewed. I have had good luck re-bleeding all four wheels with fresh fluid after tapping/ rapping the differential valve a few times to help it return to center.

You should be able to push the pistons in the wheel cylinders all the way together except for the little spring that is in between them. The rubber boots should be WAY compressed when you do this.

On Saturday I decided I was in over my head and took it to a brake shop. The good news is, I did put everything together correctly (actually this was a bit surprising). The bad news is, they were stumped also. They couldn't even charge me as they couldn't find anything to fix.

Another point of interest is that if you disconnect the sensor on the combination valve, the brake light goes off. Makes me think that Shorty is correct. I'll try hitting the combination valve with a 4lb sledge tomorrow (kidding, sort of).

The Driver side drum is still running hotter, but interestingly the pads are not showing signs of being scorched. The brake shop actually thought it could be from simply needing to wear in a new set of pads. I have also wondered if the drivers side is functioning properly and maybe the passenger side is not. My thought here is that the drivers side is carrying all of the load thus getting hotter.

S

I was raised on drum brakes. They are a pain - just did the rears on my wife's van - but they aren't complicated.

The springs are supposed to retract the shoes to prevent any contact. They do not drag lightly like discs do. Glad you got them back together right.

If the shoes are dragging, there is hydraulic pressure on the cylinder. It's been replaced - and I assumed you bled the air out. What is left is the combination valve. Traditionally the light goes on because the brake system has imbalanced pressure - on side more than the other, which causes the piston in the valve to move to the lesser side and bridge a connection.

The light on your dash is telling you the brake system isn't right. One side constantly dragging isn't the problem - it's a symptom. The brake system needs to be bled on the other side to balance the piston and make the light go out. The offending brake circuit also needs to be diagnosed for high residual pressure. It probably will come right back on the first stop. Something is keeping the fluid trapped in that side of the rear brakes.

A competent brake shop would know that and have done you some good. "We don't know" is pretty lame. Check the offending brake circuit for a collasped hose, pinched line, stuck proportioning valve, or a blockage in the master cylinder. That's where the problem could be.

Shoes don't drag except in the lame shop you got no help from.

Make sure the springs are good, and that they return the shoes to the closed position.

Also, I believe the e brake strut can be installed backwards, causing the brake to heat up.

Check that strut.