'99 F150 4x4. This past weekend the right front tire seemed to lock up on quick firm (not panic stop) brake application. Gentle application no problem. No brake pad squeal when this happened... only tire squeal on the road. What might suddenly cause this? Is there maybe a pressure balance valve in the hydraulics? Any thoughts?

 

Check the rubber hoses from the front brake lines to the calipers, they get weak and either collapse or bulge.

 

Rear drum made sense since the front didn't pull left or right when this happened. Found the rear's needed to be totally rebuilt, a saga that began when the 'helpful' technician at Kauffman Tire decided the rear's needed adjusted. Ran fine for the first 10 miles of a 90 mile early morning trip.... truck started vibrating like mad. Severely overheated the right rear until I could find an open shop to remove the tire and drum and back off on the adjuster.

 

I fail to see how collapsed or bulging flex lines would cause a brake to lock up???



Did the 99 still use a proportioning valve?
(A prop valve was used before ABS to reduce pressure to the rear brakes to prevent locking them up)
Perhaps your prop valve is failing, causing more pressure than desired in the rear brakes and locking them up at lower pedal efforts.

 

A collapsed line can cause lockup because when it collapses the fluid can't return back into the system, causing the brake to stay applied. I was referring primarily to the FRONT brakes here.

99's all had rear ABS standard with 4 wheel ABS optional.

 

The front end geometry on the 97 and up I think is such that if a front wheel is dragging you don't feel it pulling the vehicle to the side like what we used to experience. My new 2000 front tire picked up a nail or something and driving on a long trip on the interstate, it slowly went almost flat and overheated and was destroyed. i never felt it in the steering. I finally noticed the noise it was making and pulled into a gas station. i had owned the new truck two days when this happened.

 

Took it back to the shop for inspection of the rear brakes, checked everything to be correct and backed off on the adjusters. In a short trip less than 10 miles this dropped the drum temps by 100 deg but it still seems there is a problem, maybe just on the right rear.

After a second test run the right rear temp was between 30 and 50 degrees hotter than the left, don't know if this would continue to rise on a longer trip or not. Is it possible that a partial blockage in the hydraulic line to the right rear, weak return spring, or sticking wheel brake cylinder would cause the brake to get tighter as it gets hotter?

Gotta find another shop with a mechanic that knows how to trouble shoot drum brakes!

 

I wouldn't just back off the adjusters. I'd adjust them correctly. The difference in temps could be a difference in adjustment.

 

How are drum brakes adjusted now days? Back when I was doing this myself it seemed the rule of thumb was back off the adjuster until there was just barely any drag as the wheel was rotated, but this seems to make them run to hot as they warm up a little.

 

There should be no drag these days.

 

Have a 99 F150 Lariat, 4x4, 5.4L
Took to shop for rear brake service, replaced drums and shoes, overheated (300+ deg) on short drive home. Back to shop the next day, installation re-inspected, re-adjusted. Still overheated on the short drive home.

Took to a different shop. Replaced the brake springs and adjusters, test drive.. still overheated, re-examined and determined incorrect drums or shoes or both. My truck has a build date in Nov '98, was told there are 3 different rear brake specs for the '99 model years and they'd have to find the correct ones for this vehicle.

Is this true? Has anyone encountered this situation? How do you find the correct parts when these parts suppliers only tell you it will fit a 99 both nothing about the specific model build date.

 

The saga continues, the rear drum, shoes, springs, and adjusters were all replaced and continue to overheat. Looks like incorrect drums or shoes or both were installed. Apparently different specs for different build dates exist for drum brakes in this model year. Currently waiting for correct? parts to be installed... Hopefully that resolves the issue.

 

Might be worth doing a thorough brake fluid flush. Contaminated (moisture) fluid will expand with head and can apply the brakes on its own

 

Seems both the drums and shoes weren't the proper ones, apparently the supplier didn't take the time to verify the correct parts for the build date of my truck (Nov 98) and they changed sometime in 99.

Long story short. New springs, shoes and drums worked much better but the rears seemed to be doing to much work on gentle stops (drums much hotter than rotors doing a quick temp check after stopping) and left drum 50 deg hotter than right. Ask mechanic to back off the left a little but he just gave it a spin. Tested 'em out on a long drive and the right was now hotter than the left by 100 deg, actually the temp on the left seemed about right in my mind... just a few degrees hotter the front rotors. Now debating whether to back off on the right a little or tighten the left back up a couple clicks to better balance the amount of work the rears are doing.

Would really like more balance in the breaking for slick road conditions.

Anyone ever done this??