'97 GMC Drum Brake Trouble...HELP!!!!

[coburja]

Guys, I'm at a complete loss for some trouble I'm having with the rear drum brakes on my 1997 GMC 3/4 ton 4x4. Despite replacing the drum, shoes, hardware and the brake cylinder, the driver's side rear brake is overheating. The other side seems fine. They were both set up with equal drag...actually lighter drag than I would usually dial in. The passenger side seems to be fine but after driving it for a day and I pull into the garage, the driver side rear is hot, smelly, and starting to squeal. The backing plates had some minor grooves that I mostly polished out with an rough Scoth-brite disc on my die grinder. You could still feel a slight indention but no hard grooves. Do any of you have any ideas what could cause one side to overheat so badly. \

Also, best that I can tell the E-brake is working smoothly. When I've had it up on stands, you can grab the cable in front of the brake and pull it and it easily actuates the mechanism and then releases. I'm out of ideas and hate the idea of taking it to a shop. HELP!!!!

 

[DHS]

Rubber line?

 

[coburja]

The common rubber line to the rear end appears to be in good shape and everything else is hard lined. I would think that if the rubber line was bad, since it's a common line before splitting, it would affect both brakes...which it's not. It's one piece I haven't replaced and that may be next.

 

[lotsoftools]

Everything on the drum is new? Maybe the line between the rubber and the wheel cylinder is partially clogged. Like you said, if the rubber line was bad it should affect both wheels.

 

[rmc115]

master cylinder could be not releasing the pressure, check the opposite front corner for drag. you can crack the bleeder and see if drag goes away (you will have to bleed after checking) Mike

 

[mothgrey]

Could it be the bearing heating up on that side?

 

[theoldwizard1]

Have you tried the obvious, backing off the self adjuster ?

There are spots on the backing plate that should be greased. Raybestos used to make a special grease (40 years ago) but you can use silicon disc brake grease.

 

[bowtiepro3]

Even though the wheel cylinder is new it could be binding when the pressure is released, or the seal in it could be swollen up, and not letting it release..
If the wheel diagonally from the rear is dragging too like the previous member said it could be an issue with the abs booster.

 

[Tarheelgarage]

check your e brake again; seen plenty of these that are binding

 

[malodin]

have you pulled the drum off again to check brake liner? sometimes they fall off, then jam and constantly drag on the drum, or even a break pin popped off?

 

[383 240z]

Look close at the backing plate, in particular the 3 pads were each shoe rubs. If you see a groove in them you will need to weld it up and grind it smooth. I've used JB-Weld with great success.

This is from a AMC 20 plate. but you get the idea. Keith

 

[joe_padavano]

I've recently had this problem on my truck. The problem turned out to be an out-of-round drum. The out-of-round condition causes the brake shoes to move back and forth on the backing plate as you drive and this actuates the self-adjuster mechanism, causing the brakes to over-adjust. Turning the drum fixed the problem. Note that this was a brand-new, Chinesium drum.

 

[malodin]

I've recently had this problem on my truck. The problem turned out to be an out-of-round drum. The out-of-round condition causes the brake shoes to move back and forth on the backing plate as you drive and this actuates the self-adjuster mechanism, causing the brakes to over-adjust. Turning the drum fixed the problem. Note that this was a brand-new, Chinesium drum.

This is a really good point, chinease made or not all drums and rotors should be turned when doing a brake job, even brand new ones, anything mass produced such as brake drums have a certain amount of factory "acceptable limits". What works right out of the box might on one car not work right out of the box on another rig.

Also not sure on the gmc but sometimes shoes/pads have a front and back side inner/outter respectively that needs to be payed attention to. If you were to put shoes back together with the passenger side both of one kind and the drivers with the other you will essentially be using the longer brake shoe side constantly even when not braking as it will always have drag on it. I believe they are actually called leading and trailing shoes.

 

[383 240z]

Short shoe to the front, long shoe to the rear. Keith

 

[theoldwizard1]

In the "old days" (4 wheel drum brakes) some places used over sized brake shoes (extra thickness) and then they were ground down to match the drum, after it was turned.

I haven't seen that in over 40 years !

 

[kmacht]

This is a really good point, chinease made or not all drums and rotors should be turned when doing a brake job, even brand new ones,

I call BS on that one. There should be no reason to have to get a brand new drum turned before installing it. That brake lathe they use is probably far less accurate than the machine and fixturing used to manufacture the drums. I'm not saying you can't get a bad drum thats brand new but if that is the case, return it and get another. You shouldn't have to take wall thickness and life out of a brand new drum before using it.

Keith

 

[nosnerd]

agreed ^^

but put it on a brake lathe and bring the cutter right up and slightly drag it..i bet the drum is out of round....

 

[malodin]

I call BS on that one. There should be no reason to have to get a brand new drum turned before installing it. That brake lathe they use is probably far less accurate than the machine and fixturing used to manufacture the drums. I'm not saying you can't get a bad drum thats brand new but if that is the case, return it and get another. You shouldn't have to take wall thickness and life out of a brand new drum before using it.

Keith

Not going to get into it but most manufacturers call for it to be turned prior to instalation, were are talking a thousandth or so to true it up. I have turned many many drums and rotors fresh off the line and had them out of round. All the way from 20$ drums to highend brembo's

 

[Mischief King]

Not once in my time at a major brake and tire store did I ever turn a new rotor or drum. If you buy a rotor or drum that needs to be turned before install you should find a new parts supplier.

 

[malodin]

Not once in my time at a major brake and tire store did I ever turn a new rotor or drum. If you buy a rotor or drum that needs to be turned before install you should find a new parts supplier.

Well when the manufacturer's paper work says must be trued up prior to install or warranty is void...i dont know how to read that other than for face value? Your work at major brake and tire shops run there business like an assembly line so i can completely understand your experience of never having to turn a new piece of brake hardware, and its also the same reason i never let anyone but me touch my brakes.

I am only one person giving my experiences and i am sure there are millions who have had no ill problems not doing it. I just know what i do and what i have read with my own eyes.

 

[Mischief King]

Well when the manufacturer's paper work says must be trued up prior to install or warranty is void...i dont know how to read that other than for face value? Your work at major brake and tire shops run there business like an assembly line so i can completely understand your experience of never having to turn a new piece of brake hardware, and its also the same reason i never let anyone but me touch my brakes.

I am only one person giving my experiences and i am sure there are millions who have had no ill problems not doing it. I just know what i do and what i have read with my own eyes.

I'm not saying it's a bad idea to turn them or that cheaper stuff doesn't say to do that. Just if you buy higher quality parts you don't have to do that and personally I like high quality parts in my brake systems.

 

[c39er]

Are the E-brake cables free and in proper adjustment?

 

[Desert1957]

Remove both drums
Check the top Anchor pin area visually
If the shoes are not seated at the top / it could be this

*E-brake cable over adjusted
*E-brake cable sticking on problem side
*Brake hardware installed improperly

If both shoes are dragging / check this

*Raise vehicle enough to access rear backing plates
*With a brake bleeder wrench crack open wheel cylinder bleeder
*If fluid squirts out (not dribbles) there is pressure on the rear brakes
*Master cylinder push rod adjustment
*Collapsed rear brake hose / not allowing pressure to return

Make sure you have no left over parts (It does happen)
Basic rear brake shoe parts/ yours may not look exactly like this

Desert

 

[c39er]

Excellent advice and picture!

 

[pnut]

I have exactly the same truck and have had the same problem.

1). I had adjusters mixed left to right. The threads are opposite! This means one would tighten as I drove nd the other loosened

2) mis positioned shoes as identified above. I swapped short and long.

3) not clean and lubricated pieces.

I would bet 1) above. Happened to me.

Edit: I did have to go through 2 sets of drums to finds ones not warped new. Napa was good to take them back.

 

[Seanbev24]

Simple way to see if the drum is the problem: Swap sides and go for a drive.