Dirt Driver

I have noticed nothing unusual about the front brakes until yesterday when they made some brake noise while on the highway while not applying the brakes. I stopped and checked the passenger front hub shortly after at about 15mi total driving and it was pretty hot. Not sizzling hot, but hot enough that I can't touch it for more than a few seconds. The wheel dusts more than the driver's side and it seems to have a little drag when off the ground. I pulled the passenger side caliper/hub off and the bearings were fine with actually too little preload. The pins have grease and moved freely. Pads have about ~0.20" of lining. I was able to collapse the caliper with a c-clamp and it didn't seem abnormally hard to do. I regreased, reassembled, and set bearing preload per the FSM.

The passenger hub still gets kind of hot after highway driving. The driver's side gets pretty warm too, but to a lesser extent. The original grease wasn't burnt or melted although it looked old and like it had spent some time at elevated temps. Now it sometimes makes mild brake squeal while driving and not applying the brakes. It doesn't pull to either side and there is no noticeable drag when releasing the brakes at a stop(the truck rolls readily on the slightest incline). I bought the truck four years ago and haven't had the brakes apart or checked hub temp until now.

I'm wondering if a caliper is sticking, both are sticking, if the master cylinder is maintaining too much residual pressure, or if this is perhaps normal. I'm leaning toward calipers. What say you all?

2ToyGuy

From what I've seen, for whatever it's worth, the calipers are known to have "sticky" problems as they age.
A quick thing to verify, first, though, is the pedal adjustment. Make sure the MC isn't retaining pressure, due to pedal maladjustment. It sounds to me, though, like you've got a sticky caliper.

They're fairly easy to check for residual pressure, too. When it seems to be dragging, open the bleed valve for a second. If it frees it up, yep, something's holding pressure. It could be a rubber hose is collapsing inside when the pedal is released. Wiggle the rubber lines around, and see if it frees up. Or, it could be the MC is misadjusted, or the pedal.

Whatever the problem, check the thickness of the pads in that caliper. If it IS dragging a little, whatever the reason, likely it's worn the pad faster than the other side. You don't want to damage the rotor by dragging any metal across it due to worn down pads.

From what I've seen, the calipers aren't all that expensive to replace. Not difficult either. Just make certain you bleed the system after replacing the caliper!

Keep us up to date on what you find!
Pat☺

Dirt Driver

Thanks for the input. I'd have replied sooner, but don't think I got any email notifications.

The pads are still well within wear limits. Calipers look original and will be about $110 to replace, which is what I plan to do. The "problem" seems to be intermittent at this point (although inconclusive without more data); the last time I checked hub temp, I made a point to gradually stop without using the front brakes and the hub was only tepid. Other times I used the brakes normally from highway speed to a stop and they got damn hot. Perhaps I've mistaken heat generated from braking for a dragging caliper?

fierohink

Normal temps after braking will make the rotor and hub assembly too hot to touch with bare hands. A hallmark to a sticking caliper is one side versus the other will be different temps. So the drivers will be hot and the passenger will be so hot it’s clanking and pinging.

KZN185W

iTrader: (1)

When you brake, does it pull to one side? That is one symptom of a stuck piston(s)
Having more brake dust on one side means that side is doing more braking than the other side. I would take a look at the calipers if some pistons are stuck. it's pretty common after decades of use, especially if the calipers get immersed in water due to stream crossings or flood crossings.
If you're planning to replace the calipers instead of doing a caliper rebuild by using the Toyota caliper rebuild kit, then why go the Tundra Brake Upgrade instead?

wyoming9

iTrader: (1)

During the summer temperatures disc brakes are going to get warm.

Are you smelling the fine aroma of burning brake pads if something was hung up you would be if not seeing smoke coming off the pads.

Now if it was below freezing and your brakes are burning you have a problem

Rusty Bob

Deleted - wrong forum. Apologies.

millball

Trucks and 4Runners with automatic differential disconnect and solid drive axle flanges instead of lockout hubs, run the front drive axles 100 percent of the time, even in 2wd, and never get hot.
My 4Runners can run a hundred miles and more at 70+ MPH and the hubs and rear drums remain cool enough to lay a hand on. Hubs in, or hubs out, makes no difference.
Something is not permitting your calipers to release completely.
Do your rear drums get hot too???

Rusty Bob

My bad - this is about ‘79 R20 Pickup with solid axle and manual hubs… I’ll move it