Need some help - rear brake overheating? 1967 C10

[Knanthrup]

I'm having a frustrating time diagnosing some issues. What I thought was one problem appears to have turned in to two separate problems. I started hearing a squealing sound coming from mid or rear of truck, related to drivetrain not engine. I thought it must be the drum brake hanging up or potentially a wheel bearing. My suspicion was further convincing when I felt the rear wheels and the drivers rear wheel was extremely hot to the touch. I dug into the brakes and sure enough the left rear shoe lining was smoked, looked like it got baked at high temp. The passenger side looked totally fine. I cleaned up the parts and put new shoes on and test drove it. Noise is still there.

Further investigation and it seems like the squealing noise is coming from the center driveshaft carrier bearing rather than the brakes or axles. Ok so at least the noise seems to be identified, but now I can't figure out what is cooking the brakes!?

After my test drive I felt the drivers rear wheel and again it was wayyy too hot.

So I'm having a hard time figuring out whether the brake is hanging up or if the heat is coming from a failing wheel bearing or something else. There is no noticeable vibration or sound coming from the axle itself, but there was also no noticeable issues with the brake hardware that would cause the shoes to drag.

Any thoughts?

Below are pictures of the fried brake shoes (please note that the cracking may have been caused by me using a heavy hammer on the drum to get it unfrozen - not sure either way, but clearly it had taken a lot of heat). Also photo of the brake hardware assembled before I replaced the shoes, just in case anyone can spot something wrong with the hardware or setup.

[Molberg]

Are your ebrake cables seized?

[Molberg]

Could be wheel cylinders sticking as well...

[Knanthrup]

I don't think so but it might be worth inspecting on that wheel. Come to think of it the ebrake does work but not very well so that might be a sign. The handle feels fine when I pull it but I suppose that doesn't mean anything. I did back the adjuster off when I had the drum off, but I suppose if the cable was frozen it could have adjusted its way tight again?

If just that one rear drum brake was getting stuck, would it be noticeably resistant to letting the truck roll? I'd imagine a single rear drum might not do much?

[Knanthrup]

I'm also wondering if a bad wheel bearing could really produce enough heat to make a brake shoe look like that, or if that kind of damage would only be caused by the shoes making excessive contact with the drums?

[Daner]

Try jacking up that wheel and spinning it. You should be able to feel if there is resistance.

[Molberg]

I think you'd notice it. You could try working your e brake with the tires off and drums on.... Release it.. And note how much slop is in your cables under the truck. And if your drums are still stuck. I had to free up mine with some penetrating oil for the same problem you have. Took them off... Sprayed in one end worked it back and forth. Final spray with some lithium grease.

[Molberg]

Grab the axle and try to lift it up and down... Side to side. Should be minimal play. (Wheel bearing)

[truckdude239]

When ever i have rear drums hanging up its time fore a full rebuild new drums hardware shoes and wheel cylinders i found as an ase mechanic that if its got hot enough to smoke the shoes that the ruber in the cylinders is going to be shot as is the temperment on the drums

[evan396]

2x on wheel cylinder, the push rod on the wheel cylinder might not be retracting, and leaving pressure on the brakes.

[Knanthrup]

Originally Posted by truckdude239

When ever i have rear drums hanging up its time fore a full rebuild new drums hardware shoes and wheel cylinders i found as an ase mechanic that if its got hot enough to smoke the shoes that the ruber in the cylinders is going to be shot as is the temperment on the drums

Agreed, but is still like to diagnose the cause because I'd really hate to replace all that hardware and then smoke it again because it was a wheel bearing or stuck ebrake cable. Chances are ill have to replace other components but I want to pinpoint the cause first.

[Knanthrup]

Originally Posted by evan396

2x on wheel cylinder, the push rod on the wheel cylinder might not be retracting, and leaving pressure on the brakes.

Right but aren't the springs responsible for retracting the shoes and the cylinder, or are you thinking the cylinder is seized and the springs can't push the pistons back in? Seemed to me that the top of the shoes were all the way to the round stop when I had the drum off, but I guess it's possible.

[evan396]

Yes I believe the cylinder might be stuck and the springs will not return the shoes.

[WIDESIDE72]

Chock the front wheels, Jack up the rear, place on stands remove both rear wheels and have someone apply the brakes. See if they apply and release. Of this works ok, place the truck in gear. They should spin up enough at idle, no ned to rev engine. Have helper apply brakes and see what happens.


Rear wheel cylinders are cheap and should be replaced when doing brakes. Most times i have found they are usually stuck and not going out when you press the brake.

[WIDESIDE72]

From experience i have found that it is worth the time to bleed your brakes at least every couple of years, if not every year. You will be amazed at how much better pedal you will have. Brake fluid is hygroscopic meaning it absorbs moisture, which means the insid eof your system will rust up.

I had an uncle who was a mechanic for Schlumberger from the 60's to 80's. He would get 200-300k miles out of his vehicles due to a strenuous maintenance schedule. He said he very rarely ever replaced more than pads/ rotors/ drums due to bleeding brakes anually. He also changed auto trans fluid/ filters every 30k miles. He swore by Wix filters. I do too now!

Unfortunately he is no longer with us. He was a wizard at setting up third members. He could take most of, if not all of the "howl" out of most junk i took him!

[WIDESIDE72]

Something else non related i wanted to share was as a kid in the 70's/ 80's i noticed all his cars always had the headlights on. He said researchers found it prevented accidents and since he did it to all of the company vehicles, he did his pov's as well. 30 yrs later we have factory daylight running lamps!

[Knanthrup]

Ok quick update...

I've confirmed that it's a brake problem and not a wheel bearing. I did end up replacing the brake cylinder and the hardware. I had a hard time getting the rear brakes bled - the brake pedal was firm but nothing was coming out of the bleeder in the rear. After some research I concluded that it must have been due to the "check valve" in the brake distribution block that must have taken the rear brake circuit out of function.

Anyhow i decided to take it for a short drive that way, knowing that the rear brakes would not be functioning and therefore if the wheel did not get hot this time then that proves that it was a hanging brake. The wheel was cool when I got back so I was happy to at least know it wasn't a wheel bearing.

Now, the frustrating part is that I did finally get the rear brakes bled and functioning and went for a drive and that same wheel is getting extremely hot again meaning the brake is hanging again now that it's been bled.

So what else could be going on now? New wheel cylinder, new hardware, freshly bled. Confirmed that the ebrake cable was not hanging. The lines back there are metal hard lines not rubber so can't imagine it's a line issue? I suppose it must come down to either the hydraulic cylinder is not retracting or maybe the ebrake click adjuster is tightening the brake too much? Anyone have other ideas?

[nds1968]

There is one rubber line for the rear brakes. It should be hooked to a T-fitting coming from the frame crossmember.

[WIDESIDE72]

Originally Posted by nds1968

there is one rubber line for the rear brakes. It should be hooked to a t-fitting coming from the frame crossmember.

x2

[Molberg]

When you installed the new shoes and bled the system... How tight did you set the brakes up? If it was dragging the drum at all it will produce heat.

[Knanthrup]

I think I set it fairly loose to start with, and intended on letting it tighten itself with the drive in reverse/brake method. I set it loose enough so that I could put the drum on and did not tighten it any more after. Perhaps I should try loosening it more?

[Knanthrup]

Originally Posted by nds1968

There is one rubber line for the rear brakes. It should be hooked to a T-fitting coming from the frame crossmember.

I will look for that, although logic tells me that if it's before the T-fitting then it's probably not the issue, otherwise it would be hanging up both brakes.

[luvbowties]

Originally Posted by Knanthrup

Ok quick update...

I've confirmed that it's a brake problem and not a wheel bearing. I did end up replacing the brake cylinder and the hardware. I had a hard time getting the rear brakes bled - the brake pedal was firm but nothing was coming out of the bleeder in the rear. After some research I concluded that it must have been due to the "check valve" in the brake distribution block that must have taken the rear brake circuit out of function.

Anyhow i decided to take it for a short drive that way, knowing that the rear brakes would not be functioning and therefore if the wheel did not get hot this time then that proves that it was a hanging brake. The wheel was cool when I got back so I was happy to at least know it wasn't a wheel bearing.

Now, the frustrating part is that I did finally get the rear brakes bled and functioning and went for a drive and that same wheel is getting extremely hot again meaning the brake is hanging again now that it's been bled.

So what else could be going on now? New wheel cylinder, new hardware, freshly bled. Confirmed that the ebrake cable was not hanging. The lines back there are metal hard lines not rubber so can't imagine it's a line issue? I suppose it must come down to either the hydraulic cylinder is not retracting or maybe the ebrake click adjuster is tightening the brake too much? Anyone have other ideas?

"...have other ideas?" Examine the hard line in rear, esp. going from the TEE to the suspect brake. Check closely for a partly flattened section/spot on the line that could cause restriction and possibly act as a 1-way valve, letting fluid TO whl-cyl but not FROM the cylinder. Also look for rust: it could flake off inside and end up in a wheel cylinder and cause pistons to refuse to retract. A line does not have to be rubber to possibly fail internally and cause symptoms such as yours. Replacing your rear steel lines, tee, and rubber connector line should not cost that much.

Also, you said you wanted to diagnose 1st and then repair. Well, not being disrespectful, but let your pride go, finish the job, and then enjoy driving it while you have the remainder of your life to diagnose which one "fixed it". Who knows, while replacing these 50-60 year old parts, you may very well uncover/discover the problem.

In the meantime, take a look here:>> http://www.pbase.com/nufsed/drumbrake <<. It should put some anxiety at ease re: proper assembly of hardware.

HTH,
Sam

[Knanthrup]

Ok update time, hopefully this will help someone down the line...

I went through a lot over the last few days with this thing. One thing that I discovered was that I didn't have the smaller shoe on the facing the front, I fixed it but that didn't make any material difference at that stage.

The next test method I used was to pump up the brakes, confirmed that they were sticking the drum, then cracked the bleeder open to see if it was hydraulic pressure still holding the brake. If there was hydraulic pressure then it must be a problem in the lines, if no pressure then I figured it would be a brake hardware or mechanical issue.

There was pressure to be relieved and when I did, the brake unstuck. So at this point the next thing to check was the lines. First suspect was the flex hose since it was the only rubber piece. Pulled it off and in the process I managed to crack the hard line that runs along the frame rail, found out just hor brittle those 45 year old lines were, plus the ends fitting threads were damn near frozen.

So, several trips to and from the parts store and I put together a line that could replace the front to rear frame rail hard line and replaced the flex hose with it.

Alas, the system seems to be working again! The rear drum no longer hangs up! Now I still have to bleed the system a bit more but the rear brake appear to be functioning and releasing.

One other thing that is pretty funny... When I got the truck recently, I always thought the brake pedal felt wayyy too stiff and required too much effort but I wrote it off because I figured that's how an old non power drum brake system felt not having anything to compare. As it turns out, the line must have been clogged both directions and I was having to push the pedal against that blocked force far enough to actuate the front brakes to actually stop me. Now the pedal actually has a softer feel to it and requires much less effort.

Thanks for everyone for their contributions and suggestions, looks like some of you were spot on.

[elf w/capital T]

Originally Posted by WIDESIDE72

Something else non related i wanted to share was as a kid in the 70's/ 80's i noticed all his cars always had the headlights on. He said researchers found it prevented accidents and since he did it to all of the company vehicles, he did his pov's as well. 30 yrs later we have factory daylight running lamps!

Both posts are great. Thank you for refreshing our mnds.

I recently did a rear end swap and told my girl almost the same things you mentioned

Brake fluid doea hold moisture hence why the discoloration and obvious FEEL when flushed