Drum Brakes pull left when hot only

[demian5]

I have a 70 c15 with coil rear.

New front linings and drums. Adjusted to duplicate drag on both (touching, then backed off just enough not to touch). Bearings are good, lubed and adjusted properly.
Front tires both at 35 PSI and rears at 32.
Had front alignment performed about 2 months ago. He did what he could and recommended upper ball joints soon.
Front suspension pretty solid. I greased all the fittings well when I did the brakes a month ago.

Rear not too old and adjusted properly about 6 months ago.

When cold, stops straight and perfect.

When hot (driven and stopped a few times) pulls to left. If a panic stop, locks up left front and will jerk wheel out of hand if not ready.

Left front wheel feels way warmer than right front after driving.

Replaced leaking booster when I first got the truck, but still has little feel of power assist.

All brake components were pretty new when I got the truck. I'm almost thinking a failing brake hose on left front.

My plan is scarebird disc brake conversion, but till then, I know I can remedy this, however I am hoping someone else out there has some insight.

I know drum brakes you need to be "prepared" when stopping, but for it to go from "man this stops great" to "@#$@$#%@# %#$@%!"... not fun...

Thanks in advance!

[skinnan]

did you replace the brake hoses? That would be the first thing I'd do

[leftybass209]

Originally Posted by demian5

I have a 70 c15 with coil rear.

New front linings and drums. Adjusted to duplicate drag on both (touching, then backed off just enough not to touch).
Had front alignment performed about 2 months ago.
When cold, stops straight and perfect.

When hot (driven and stopped a few times) pulls to left. If a panic stop, locks up left front and will jerk wheel out of hand if not ready.

Left front wheel feels way warmer than right front after driving.

Replaced leaking booster when I first got the truck, but still has little feel of power assist.

All brake components were pretty new when I got the truck. I'm almost thinking a failing brake hose on left front.

There's already too many factors to narrow it down, as any of them can cause brake pull. When you suggest something like a brake hose, I assume they weren't replaced within the last 5 years? Were all the shoes and drums matching components? Were they clean when installed? Did you clean the drums of all the anti-corrosive crap before installing? Did you get any lube or brake fluid on the linings then tried to clean it off with brake cleaner? Ball joints can cause a brake pull as well but usually it's accompanied by other symptoms like wandering or a thumping sound in the front end.

Did the lines bleed okay and evenly? Did you try backing off the left adjustment until it evens out? Did you verify any temp measurements with an IR gun?

[leftybass209]

Also, a failing hose will most likely swell under braking, causing LESS pressure getting to the wheel cylinder. Less pressure would mean those brakes wouldn't work as efficiently as the opposite side, so I can't see a failing hose causing an increase in pressure or heat at the drum.

[demian5]

Shoes clean when installing.
Drums cleaned of cosmoline when installing.
Have never bled the brakes on this vehicle since owning (it all looked fairly new when I adjusted them the first time before I replaced the shoes).

No IR gun temps (but I can), just feel.

Hoses - My thoughts...
If driver was bad and passenger was good, it would pull on the passenger side as fluid would flow better, but if driver bad, it could cause dragging brake (or if part of hose only flapping and blocked when fluid coming out, like a valve...)

I am almost thinking I have them adjusted too tight and the left is dragging after getting hot a few times... I read where people say to back them off to not touch, then back off another 8-12 "clicks". And of course the new drums nor the backing plates have adjustment holes.

If i'm going to pull the wheels again, ill replace the hoses.

[garyd1961]

Try bleeding the brakes and then backing up and applying the brakes several times.

[HO455]

My advice is to pull the drums and inspect the brakes. You may find one of the slaves is now leaking or notice an odd wear pattern on the shoes. Check to make sure every thing is assembled correctly. I have learned that the last thing I messed with is usually the first thing that screws up.
My AD truck will do this for the first 20 to 30 miles after adjustments to the front brakes, but it slowly goes away the more you drive it as the shoes wear to equal gaps.

[palallin]

Originally Posted by leftybass209

Also, a failing hose will most likely swell under braking, causing LESS pressure getting to the wheel cylinder. Less pressure would mean those brakes wouldn't work as efficiently as the opposite side, so I can't see a failing hose causing an increase in pressure or heat at the drum.

It's not that simple: it could be that the hose on the OTHER side is toast, which won't let the brakes equalize, allowing the left to lock up.

[HO455]

The problem with hose failures is when they fail internally different things may result. In one type of failure they may block or restrict flow to the cylinder or caliper so the other side does most of the work. And in another case they may let the fluid pass but not release the pressure causing that brake to drag. And then when you apply the brakes that side may grab first. This is why it is always recommended to replace both hoses at the same time.

[old51sedan]

Originally Posted by demian5

I have a 70 c15 with coil rear.

New front linings and drums. Adjusted to duplicate drag on both (touching, then backed off just enough not to touch). Bearings are good, lubed and adjusted properly.
Front tires both at 35 PSI and rears at 32.
Had front alignment performed about 2 months ago. He did what he could and recommended upper ball joints soon.
Front suspension pretty solid. I greased all the fittings well when I did the brakes a month ago.

Rear not too old and adjusted properly about 6 months ago.

When cold, stops straight and perfect.

When hot (driven and stopped a few times) pulls to left. If a panic stop, locks up left front and will jerk wheel out of hand if not ready.

Left front wheel feels way warmer than right front after driving.

Replaced leaking booster when I first got the truck, but still has little feel of power assist.

All brake components were pretty new when I got the truck. I'm almost thinking a failing brake hose on left front.

My plan is scarebird disc brake conversion, but till then, I know I can remedy this, however I am hoping someone else out there has some insight.

I know drum brakes you need to be "prepared" when stopping, but for it to go from "man this stops great" to "@#$@$#%@# %#$@%!"... not fun...

Thanks in advance!

Had the same problem with mine, pulled to the left. The right wheel cyc was froze up.

[demian5]

Originally Posted by old51sedan

Had the same problem with mine, pulled to the left. The right wheel cyc was froze up.

I ordered hoses and will check that before I replace. The curious thing is it is fine and stops dead straight when cold or it has been sitting.

[mike16]

I'm also going to bet that a wheel cylinder is leaking or maybe stuck wheel cylinder pistones. dont just bleed the brakes but flush the system.

[demian5]

Originally Posted by mike16

I'm also going to bet that a wheel cylinder is leaking or maybe stuck wheel cylinder pistones. dont just bleed the brakes but flush the system.

I had the drums off a week ago and nothing was showing signs of leaking. I may just get two new ones when I do the hoses.

[garyd1961]

Bleeding the brakes is easy and simple, it may just fix your problem. I put new drums shoes and master cylinder on my 1970 not long ago. I rebuilt the two rear wheel cylinders because one was leaking. I have new wheel cylinders and hoses for all around but couldn't get the lines loose so I left them for when I have more time. Anyway I thought I had everything good to go but kept having problems like you are having until I went back a bled the system again. I also got in the road in front of my house and backed up several times applying the brakes firmly but not stomping on them. They work like a brand new truck now.

[demian5]

Originally Posted by garyd1961

Bleeding the brakes is easy and simple, it may just fix your problem. I put new drums shoes and master cylinder on my 1970 not long ago. I rebuilt the two rear wheel cylinders because one was leaking. I have new wheel cylinders and hoses for all around but couldn't get the lines loose so I left them for when I have more time. Anyway I thought I had everything good to go but kept having problems like you are having until I went back a bled the system again. I also got in the road in front of my house and backed up several times applying the brakes firmly but not stomping on them. They work like a brand new truck now.

Great info. I'll try it!

[AnotherWs6]

My truck does the same thing, doesn't seem to care if brakes are hot or cold. It's like they have a mind of their own. My professional mechanic friend and I went over them and adjusted them, all seems well. But if I need to panic stop the driver front wheel locks and tries to rip the steering wheel out of my hand. SOMETIMES. I don't get it.

[skinnan]

Originally Posted by palallin

It's not that simple: it could be that the hose on the OTHER side is toast, which won't let the brakes equalize, allowing the left to lock up.

that was my thought....besides, brake hoses are cheap

[demian5]

Originally Posted by skinnan

that was my thought....besides, brake hoses are cheap

Already bought them...

[sleepertruck72]

From my experience brake pull in one direction is usually an opposite side brake component that is defective... caliper, wheel cylinder, hose etc...You can drive it a short distance and then jack the front end up. Apply the brake pedal and attempt spinning the wheels... to check for dragging brakes.. seized calipers, wheel cylinders, etc... hope this helps..Im curious to find out the issue

[demian5]

So I was thinking "well its only after driving a bit and they pull, and I know the brake line on the passenger side is really close to the header on every truck this era I have seen.

So here are the picture of my brake lines. On the driver side for the front and rear was too hot to touch... I feel the one under the truck on the right will get better airflow (fuzzy in this picture)but is still close. I may wrap in heat reflective material until I can do my disc brake conversion...

I may just wrap in an aluminum can to see if it makes a difference before doing anything else.

Thoughts?

[rockyrivermark]

Here's but I just went through with a similar problem and what my solution was. I have front disc though
I had dragging brakes after resto of truck that sat for a few years. both front and back but front way worse.
Replace rear wheel cylinders and front calipers.
Problem seemed gone but once driving around a bit brakes would drag. Not as bad though.
Changed master cylinder but problem ended up being the rod that comes out of the booster and pushes into the master cylinder.
I took come measurements and found the adjustable rod coming out of the booster was 5/16" too long so there was always hydrolic pressure. Not sure why it for worse when hot though.
Screwed on the adjuster and prob solved.
For you wheel cylinders at $12 so I would change that either way.
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[demian5]

Update on condition:

When truck is first driven, brakes are fine. After driving a bit it starts pulling left hard still. I got on them and locked them up last night to see what it would do and the rear wheels locked up and the truck pulled hard left.

All adjusted good, all working fine. Could that rear brake line be getting heated up where it curls under the frame by the headers enough to cause a drag on the rear?

[TCLARK]

Originally Posted by demian5

Update on condition:

When truck is first driven, brakes are fine. After driving a bit it starts pulling left hard still. I got on them and locked them up last night to see what it would do and the rear wheels locked up and the truck pulled hard left.

All adjusted good, all working fine. Could that rear brake line be getting heated up where it curls under the frame by the headers enough to cause a drag on the rear?

just for S#$%* and giggles switch the hubs from left to right. I had one side on the rear locking up and switched them and it stopped ????

[hamjet]

I think rear wheels are locking up on hard braking because all weight is shifting to the front and the rear is lifting, putting less weight over the rear tires. I believe its common with these old trucks. I had an 85 dodge caravan that had a sensing system at the rearend that would change the amount of braking pressure depending on if it was loaded or empty. Did you wrap the lines near the exhaust when you tried it?

[demian5]

Update: Been driving and dealing with pull. Decides to check all fluids, front reservoir on master was full, rear empty = needs a master.

Replaced, braking better, still pulls.
Checked rears, look fine, braking evenly when applied.
Checked fronts, drivers trailing shoe worn to the metal almost, front shoe worn too. Passenger side fine.
Even application of braking in front (when cold).

I am going to replace the front shoes, wheel cyls and hoses (even through no leaking and they all look recently replaced). All i can think is that when the front brakes get hot, the front left wheel cylinder sticks.

That's all I can think of (unless there is a MAJOR groove in the backing plate but that would cause other issues as well.