Drum Brake Issues

[Janz99]

Hey guys, I have a 68' that has all four drum brakes and a relatively new booster/master cylinder (previous owner installed).

I have been daily driving this truck for the past couple of summers and have never had brake issues. A few weekends ago my son and I took the truck out camping and on our way I noticed the brakes were dragging slightly.

By the time we got to our camp site the brakes had basically seized on and two of the four drums were smoking. I couldn't tell if all four of the drums were seized or just the two smoking drums as I didn't have a jack with me at the time.

I let the truck cool down for about an hour and was ready to call a flat bed to tow it home. Decided to start the truck and see if I could move it and luckily the brakes had let go.Drove the truck around for the rest of the weekend and for the following 3 weeks without it happening again.

Last night on my way home just as I was about to pull into my garage, I noticed the brakes were starting to drag again. I was able to park the truck but again I was short on time and wasn't able to confirm what wheels were locking up.

My question is, since its a drum/drum setup, is there any sort of valving inside the distribution block that could cause this, or is this strictly a master issue? I think I can rule out wheel cylinders due to the fact that it happens to more than one wheel at a time? Any suggestions on where to start the trouble shooting the issue would be greatly appreciated.

[68Gold/white]

I'm assuming the 2 drums dragging were either both front or both back???

How old are the brake hoses??? Both fronts and the lone rear...

Brake hoses can be a problem, especially older hoses, not likely the valve...

[Janz99]

Originally Posted by 68Gold/white

I'm assuming the 2 drums dragging were either both front or both back???

How old are the brake hoses??? Both fronts and the lone rear...

Brake hoses can be a problem, especially older hoses, not likely the valve...

I can't confirm exactly which drums were dragging, it could have been all four, however, one rear and one front were smoking so those two were definitely dragging hard.

I've owned the truck for the past 4 years and have not replaced the flexible brake hoses, they do "look" and feel solid though, no cracking or indication of collapsing.

[Happy_dan]

My brake hoses looked good from the outside. I decided to replace them anyway. They looked bad inside and possibly collapsed. Not sure that is you issue by any means but I would not trust old rubber brake lines.

I think if the master has problems, you are more likely to have a low or soft pedal but I am no expert. That is what happened with mine.

[gmc684x4]

Is there any bulging of the hoses that could also pinch of the line and keep brakes locked I would suspect back brakes more the culprit since you where driving and didnt notice a real heavy drag

Front brakes are primary stopping power if they dragged you would notice it

Anouther item to check are emergency brake cables they can stick as well

[Janz99]

Originally Posted by gmc684x4

Is there any bulging of the hoses that could also pinch of the line and keep brakes locked I would suspect back brakes more the culprit since you where driving and didnt notice a real heavy drag

Front brakes are primary stopping power if they dragged you would notice it

Anouther item to check are emergency brake cables they can stick as well

I have checked the hoses and haven't seen any bulging, I haven't ruled out hoses but they don't look all that old to me. By the time we had gotten to the camp site, yes there was very heavy drag and I needed to stay on the gas to keep the truck rolling. Once we stopped they were literally on so hard that I could not move the truck anymore and why I had considered having it towed.

[gmc684x4]

Pull drums off ones dragging should have a more burnt smell and may show heat discoloration

[Steeveedee]

If you had front and rear brakes smoking that makes me suspect the brake free pedal adjustment. If it's just tight enough, as the brakes heat up they will begin to drag. After the first time, did you drive it any kind of distance? Driving some amount of distance gives the brakes more of a chance to get hot, and to start dragging again.

While the hoses may be bad inside, I'd think that all three being bad and causing the brakes to drag at the same is pretty low probability. Not saying it can't happen. Recent...ish replacement of the master and booster is the clue that maybe the brake free pedal is insufficient.

[gmc684x4]

I would think that would have shown up sooner as Jan'z has had his truck several years

Parking Emergency brake cables are suspect too i have had them lock up both, one side stick been a passenger in a van that the owner left the parking brake on and start his van on fire luckily it was winter and lots of snow to put on the back brakes

[68Gold/white]

Anything is possible, I wouldn't waste any time trying to look at the outside of the brake hoses, trying to make a diagnosis. Not trying to sound like a "Beavis", here. Hoses can look new, for 10-40 years. Hoses typically collapse internally, not allowing brake fluid to go back and forth inside the hose, creating a clog, potentially putting the "Smoke" to the brake shoes OR pads.

I replaced the front hoses, Saturday on my buddies, newly acquired 71 C-10. His hoses didn't look any where new, BUT got replaced to make sure the 71 is reliable, for a long time to come.

Make sure the adjusters are adjusted properly, if one gets stuck, it will do, what you are experiencing.

In the process of repairing this, I'd get all 3 brake hoses, and replace them some time soon, even if they are not the problem...Drum brakes stop many vehicles, it's the emergency stops that can eat your shorts. You want your brakes at the very best, all the time, and there's no way one should take a chance with drum brakes...

[Janz99]

Replacing the brake lines is definitely on the list of things I would like to replace during this repair. I just want to nail down what the actual problem is first before starting to throw parts at it. This is my first experience working on a drum brake vehicle so my inexperience is showing through here

The e-brake has not been hooked up for the past few years as the dual exhaust is in the way of the stock cable. Since I know at least one front and one rear brake were locked up, I can rule this out as being the issue.

I have easily put 8-10000km on this truck over the past 3 years. I literally daily drive the truck and have taken it on multiple 5-600km round trips.

At this point I'm leaning towards either the master being bad or the distribution block. Since I have no clue what is internal to the dist. block its hard for me to rule it out. I will say that the dist. block is very close to the exhaust manifolds (LS swapped) on this truck. Its in the stock location but with stock LS manifolds it puts it within a few inches of the manifold.

[gmc684x4]

On a v8 install the block would still be about the same distance away

No ebrakes the cable can still be pulled and possibly stuck in brake apply postions

I would be looking at how to reconfigure ebrakes as they are a safety device

I agree a faulty master would more likley to be more mushy

Change your brake hoses first as there most likely the main issue
There cheap to replace

Wheel cylinders are cheap to

Nothing like driving through friday traffic and have a brake hose fail is a experiance i do not wish to repeate

[Janz99]

Originally Posted by gmc684x4

On a v8 install the block would still be about the same distance away

No ebrakes the cable can still be pulled and possibly stuck in brake apply postions

I would be looking at how to reconfigure ebrakes as they are a safety device

I agree a faulty master would more likley to be more mushy

Change your brake hoses first as there most likely the main issue
There cheap to replace

Wheel cylinders are cheap to

Nothing like driving through friday traffic and have a brake hose fail is a experiance i do not wish to repeate

I agree, having a working e-brake is also on my list. Id really like to upgrade this truck to discs at some point and was hoping to do both at the same time.

Maybe I am over thinking this and a few brake lines will be an easy solution.

[gmc684x4]

Front Disk Drum Upgrades are easy and can be cheap to do if you can scrounge parts from pick a parts craigslist etc

I am using parts of a 95 G20 Van it has new rotors and brake job going to use them on my 72 spindles I am going to install on my 69 C20 Chassis and make it into a C10 and use the rear drums as well in the swap as they are the 2 3/4 shoes on them checking parts on rock auto same as 79 c10 front and rear calipers rotors drums wheel cylinders

I am planing on hydro boost as well since i have a setup out of a 99 van

you can get 6 bolt aftermarket rotors for your truck

whether you use a kit or build your own disc upgrade you have to insure all the pieces will work together

A mix matched master cylinder to a universal brake booster with wrong proportioning valve can cause a lots of issues

http://67-72chevytrucks.com/vboard/s...d.php?t=444823

http://67-72chevytrucks.com/vboard/s...d.php?t=456889

[gmc684x4]

If your keeping it 6 bolt wheels you can also look at late model trucks to donate there rear disc brakes
Need longer wheel studs

I was planning this route until i got a complete rolling 5 bolt chassis

[Janz99]

Originally Posted by gmc684x4

If your keeping it 6 bolt wheels you can also look at late model trucks to donate there rear disc brakes
Need longer wheel studs

I was planning this route until i got a complete rolling 5 bolt chassis

Is there a conversion bracket available to make the late model discs work or is it a custom install?



Here is the latest update on my brake saga. I noticed on my way home from work today that the pedal feel was getting stiffer and stiffer the longer I drove. The brakes weren't dragging, yet, but the pedal was very stiff and had almost no free stroke.

I stopped to pick up the kids, as soon as I started to back the truck out of my parking stall I could feel them dragging. By the time I got home they were almost completely locked again. I managed to get a jack under it and check, all four wheels were completely locked up.

To me this would indicate a master issue, no? I don't see any other way that all four wheels could lock up like this if it wasn't. It would be one hell of a coincidence if all 3 brake lines were collapsing at the same time, or if all four wheel cylinders failed at the same time.

Id love to here what everyone else thinks.....

[LockDoc]

-
Is there a return spring on the brake pedal? It sounds like the pedal may not be coming back up far enough to release the pressure on the system. Next time it builds up pressure and the brakes start dragging put your left foot under the brake pedal and pull up on it. If that is the problem that should release it.

Another thing you can try is when the brakes are locked up open one bleeder on the front and one bleeder on the back and see if it releases the lock up.

Just some easy things to try.

LockDoc

[RichardJ]

Could be the booster pin adjustment. I always check pin adjustment, but I had a problem a couple of years ago. 6 months after changing a booster, I could feel a slight drag coming to a stop at traffic lights. Manual trans and I could feel it stopping itself the last couple of feet and when on a slight grade the car wouldn't roll.

I pulled the MC out and sure enough the pin adjustment had changed and was a little long,

Try loosening the two MC nuts and place a washer/spacer under each side.

If that stops the dragging, then you'll have to pull the MC out far enough to get the measurements and make the adjustment.

[gmc684x4]

Here is a pic of the brake pedal spring

Binding up can be an issue as well
you can see there is a white set of bushings on the brake pedal and is you have a vacuum booster there are pivot points there too that cab bind up

[Janz99]

Thanks for all the suggestions guys! I do have a return spring on the pedal and will check to see if its returning back to its starting position.

The booster pin is an interesting one. I didn't realize that pin was adjustable (ive never had it apart on this truck), I plan to redo some of the brake lines if I have to replace the master so measure and adjust when its apart.

-Ryan

[SJLenz1340]

I still have 4 drums, adjusted all and then had a similar problem. Given the age I replaced everything on the rear, springs, shoes, drums, adjusters, hose, wheel cylinders, and e brake parts. After all that my rear brakes work great, and with such a grand success I have all the same parts ready for the front.
It is my opinion that I had perhaps several issues, 1) worn out adjusters 2) failing wheel cylinders, the muck that came out of there was bad 3) I also suspected the brake hose, seen that fail before.

[68Gold/white]

The crazy thing about this problem, is that it just cropped up, and it's not a normal "brake" problem. This problem DOES happen, but this seems strange.

Any chance someone (or a shop) added brake fluid to the master cylinder, AND that it may not have been brake fluid??? I know of an instance where this happened at one of those "Quick Lube" places.

Just make sure you purchase a New master cylinder, Don't fiddle around with a reman, you WILL regret tat!!!

[gmc684x4]

Gold has a good point i never experienced it i have heard of it happining

Most petrol based fluids will also have made the master cylinder cover rubber to expand
Say power steering fluid accidentally added will also expand master cylinder seals which can block fluid return as it warms up

[Janz99]

Picked up a new master cylinder today on my way home from work. Got everything apart and I THINK i found the issue.

The brake booster I have has a piston/push rod that is removable. It sits inside a little rubber bore that the pedal linkage pushes on. That push rod was stuck inside the the back of the master cylinder. It took some WD40 and persuasion to get it out.

So what I think was happened is that the piston portion came out of the bore (maybe even at the last brake bleed) and got wedged inside the booster. That's probably why the pedal always felt pumped up.

Im going to replace this master just in case but I think that stuck pushrod/piston contraption was the issue. Going to redo a few hard lines to clean things up a bit and then hopefully get it back together this weekend.

[RichardJ]

If I understand what you are saying, it sounds to me that you need a new booster and not the MC.
Pictures of what you have would be useful.
If you do use that new MC make sure the MC bore diameter, is the same as the one you had. Don't listen to any crap about disc or drum MC. Just make sure it has the same bore.

A manual brake MC will have a deep hole in the rear of the piston. A MC for a vacuum booster setup will have very shallow hole.

Some MC are sold with an adapter plug so the MC could be used for manual or power.