Strange brake dragging problem

[MikeB]

After 50 miles or so of driving and stopping, especially from higher speeds, the left rear shoes on my 82 C10 start dragging. When I let off the gas to slow down, the brakes seem to lightly pulse – “grab, release, grab, release” with each revolution. Acts like a high spot on the shoes and a high spot on the drum are lining up once per revolution. I know it’s the left rear because the wheel center on that side is 40-50 degrees hotter than the right side.


However, when I get the truck up on jack stands the wheel spins freely. And if I drive the truck a few hours later, there is only a slight hint of the problem. Drums shoes, and wheel cylinders have less than 2K mile miles on them. Shoes fit the drum curvature perfectly. Rear hose is new, and the right rear is fine. I don’t know if axle bearings have ever been changed, but there is no seal leak. Pulling the drum shows nothing strange. If I back off the adjustment, the problem goes away for a while, but self-adjustment brings the shoes closer and the problem returns. I’m wondering if the brake drum is going out of round when hot. I'm very close to replacing drum, shoes, wheel cylinder and axle bearing on that side.

Any suggestions?

 

[Blue Ox]

The beauty of twin engines in a boat, and R & L interchangeable brake parts, is that you can swap pieces from side to side, using a "known good" part to diagnose a problem.

 

[MikeB]

Just occurred to me that maybe the axle bearing is spinning in the tube. I once saw this problem with a 8.2" 10-bolt when I went to pull the bearing and it almost fell out! Don't know what the symptoms might have been, because I bought it from a guy had who bought it from a guy a few years before. But I'll bet there was a lot of heat being generated!

 

[1987 GMC Jimmy]

Maybe the drum’s severely out of balance, and that’s why it spins fine, but you can’t replicate the speed necessary to make it show up. Are the weights still on there?

 

[Bennyt]

The temp may be warmer because its actually working and heating up and not necessarily a bad drum/ bearing. I would try swapping drums side to side to see what happens. A drum and or bearing is cheap enough and easy enough to replace that I would just do it if you have any doubts. If you are thinking out of round or out of balance at extended load; you can find a shop that does on car wheel balancing to check it. Haven't seen that done in 20 years though but VW shops used to balance a lot of the wheels and hubs on the car.

 

[MikeB]

Thanks, guys. Got that recommendation to swap the drums from a friend and MP Brakes as well, so it sounds like a plan.

Took the truck for a 3-4 mile drive this morning and didn't get the "grab, release, grab, release" that I got yesterday after freeway driving. Also, measured the temp of the drum edges near the backing plates. Are you ready for this? 104-113 on the passenger side, but 185-223 on the driver's side! So definitely dragging a little after a bunch of self-adjustments. Must have been 250 or more yesterday on the freeway.

 

[MikeB]

Swapped the drums from left to right and the problem followed the drum. Only thing I can think of is the drum gets out of round due to the heat generated by driving and braking. When at ambient temperature, it slides off and on the shoes easily, just like the other one. No sign of dragging on the drum or shoes.

Interesting that the "bad" drum had a lot more surface rust than the other one, even though both were the same store brand installed at the same time. Must have been from a different batch or a different Chinese communist supplier.

Just ordered a Raybestos drum from Rock Auto instead of the store brand drums at my local auto parts stores. I've always had good luck with Raybestos and Wagner, no matter where they are made.

 

[1987 GMC Jimmy]

Only thing I’ve used of theirs is a Raybestos new production master cylinder, and it’s been GTG!

 

[Blue Ox]

Swapped the drums from left to right and the problem followed the drum. Only thing I can think of is the drum gets out of round due to the heat generated by driving and braking. When at ambient temperature, it slides off and on the shoes easily, just like the other one. No sign of dragging on the drum or shoes.

Interesting that the "bad" drum had a lot more surface rust than the other one, even though both were the same store brand installed at the same time. Must have been from a different batch or a different Chinese communist supplier.

Just ordered a Raybestos drum from Rock Auto instead of the store brand drums at my local auto parts stores. I've always had good luck with Raybestos and Wagner, no matter where they are made.

The phrase "bad casting" comes to mind, and I'm not talking about fishing.

All kinds of things happen to castings. Not just metallurgy. There's a reason they don't use castings on aircraft.

Good that you found the problem. Thanks for the update.

 

[Rusty Nail]

Combi kits cost seven bucks. You didn't mention new springs...

*edit*
Still pondering this.
I think that argument is valid. It may be out of round / warped or whatever you wanna call it BUT!
I would not have replaced it.
I do NOT believe it is very likely to be from "a different batch" .
That said - without new information , if the brake springs ARE oe, sure your new drum will magically solve the problem - until it reappears in the same manner at the cost of a new drum because the seven dollar problem remains.

If it were ME , I would buy a combi kit and ensure the new springs are installed correctly and turn that old drum and try again.

You might end up ahead!

Did I miss information re:brake cylinders?
Do you verify their correct action? (Extension)

Better yet @MikeB , is there any, or did YOU, grease the backing plate?
There has got to be what, three or four spots for brake caliper grease there AND , especially with that localized HEAT, if you used the wrong grease, it may no longer be present having actually melted and joined to the braking surface of the drum.
I see a potential issue.

Maybe Mike, you could fix it for FREE providing you turn the drum again.

I know. I know.... PITA but It is super easy to install brake springs wrong. They get weak and cause mystery compounding brake problems but people skip them because its hard and called a combi kit haha.

Dont forget the backing plate needs grease.

Hope this helps!

 

[AuroraGirl]

Also, make sure a emergency brake cable isnt causing some issue? My f150 had a driver side kink in the cable to apply some pressure but not lock up the wheel. Overtime caused some serious inbalance. I mean, you did say it seemed to follow the drum but doesnt hurt to check everything.

 

[olnick]

Check out live and learn Brakes. Posting
I just went through the exact same problem as you! It ended up being Made in CHINA wheel cyl!

Olnick.

 

[MikeB]

Thanks for the tips guys. But I don't think I have a problem with springs, parking brake, or not enough grease on the backing plate nubs.

Yes, springs were new when I did the brake job. Wheel cylinders, too, but probably made in a ChiCom plant. When I first noticed the problem, I backed-off parking brake pre-load, but all that did was cause the truck to roll down hill if not in Park.

Old electronics technician adage: "If the problem moves with the part, then it's probably the part." But if my left rear brakes ruin another drum, I'll let you all know.

 

[Rusty Nail]

Electronics technician...

 

[AuroraGirl]

Electronics technician...

OH Lorde, you done messed up now, Mike. RUN.