I've never experienced anything quite like this before, but then again, this is my first F150. Maybe there's nothing wrong.

With most normal driving, everything's fine. Rolling stops, no matter how slow the truck gets, there's no issue accelerating. But when you come to a complete stop, then hit the gas, there is a little hesitation while a small amount of suspension windup occurs before the truck starts moving again. Never really noticed it until I spent some time in stop-and-go traffic. Now it seems like I'm towing something heavy and have to overcome that inertia every time the truck stops.

It's almost as if the calipers are hanging, but there's no side-to-side pull, no smell from the brakes, no squeaking or squealing, etc. The system was flushed with Pentosin synthetic DOT4 about 2,000 miles ago.

Anyone else experience this issue?

 

Check the temperature of the center of the wheels after driving in the city to see if the brakes are overheating.

 

Sounds like the flex lines are collapsing on the inside. I had that happen on one side of my 2012 when I did the brakes. Seems the lines collapse on the inside and will not let the pressure release completely on let off. Mine was the passenger side front, the residual pressure cooked a new rotor and pad set. Luckily, the shop that did the work warrantied the pads and rotor, i just had to replace the hoses. Next time I will change the lines when i do the brakes, just another maintenance part.

BJ

 

The spring in the master cylinder pulls the MC piston back when you release the brake pedal. This causes a negative pressure in the brake system which pulls the caliper pistons back. The brake hoses collapsing on the inside would keep the caliper pistons from being pulled back and seems to be a common problem with Fords.

 

Not correct.

Yes, the springs in the MC will push the pistons back.
But they do not pull back the caliper pistons.

The seals in the MC are specially designed to prevent pulling high vacuum in the brake lines, because the OEM does not want the MC to pull the caliper pistons back too far, causing large dead stroke on the next apply.

The caliper piston seals are designed to pull back the piston when the pressure is released.


For this issue - perhaps there is an issue with your hill start control? It is designed to hold pressure in the brakes when on a hill so you have time to get the the gas pedal. If it were holding on every stop you might feel it on flat ground.

 

Whether it's correct or not, I just had an issue on my 03 with the front brakes dragging and it WAS the hoses collapsing.

 

I've experienced the collapsed brake line issue in my 85 camaro and seen it in other vehicles as well. You can't really tell by looking at the lines either, but the wheel, or wheels, will be extremely hot after even a short drive. If you don't have a ir temp gauge splashing some water on the wheel should produce some steam or sizzle if they're hot pointing you to the likely culprit

 

Brake fluid is incompressible. Therefore the caliper pistons can only be pulled back the same distance they were pushed out with the mc piston moving the same distance in both directions. Just trying to look at it logically.

 

"... this is my first F150."

Just my first thought: could this be the drive shaft splines needing lubrication?

 

That has nothing to do with dragging brakes.

 

It feels the same as a dragging brake coming off a complete stop. Since the OP has no other dragging brake symptoms(heat, dust, etc,) why not try the shaft first.

 

I agree. It's debatable as to whether that's causing the OP's problem but it's something that needs to be done anyway so just do it and see if it helps.

As anyone tried using one if the IR thermometers to check each of the brakes after driving? I think it would be more reliable and accurate than just trying to feel the brakes. I think I'll buy one and use it occasionally. It might be a good way to spot problems before they become A Problem!

 

Thanks for all the input, guys.

I'm pretty sure it's not the hill start control or the drive shaft splines, because it's a 4x2 XL.

I do have an IR thermometer and that's a great idea. Personally I didn't think dragging brakes were the culprit, just that it has a similar feel. But who knows? It's worth a try!

 

it may be logical, but its still not correct.

due to the length of the brake lines and the fluid dynamics you will actually replenish brake fluid in the MC (master cylinder) on every brake pedal release, and then compensate it back into the reservoir after the system returns to atmospheric pressure.

In layman's terms - the MC will return fast enough to pull vacuum before the pressure returns to zero in the calipers. At this point the vacuum in the MC pulls fluid over the MC seals (replenishes) to prevent pulling high vacuum levels. Once the MC fully returns there is an open passage to the brake fluid reservoir. At this point (milliseconds later) the fluid returns from the brake lines and pushes back into the reservoir (compensates).

As the pressure in the wheel caliper returns to zero, the seals pull the caliper piston back into the retracted state. (when you apply the brake pedal the fluid pressure pushes the seal forward with the piston)

This all happens very quickly, but it happens every time you release the pedal.

This is why if you do a very quick double-pump of the brake pedal it will feel harder - you are re-applying the brakes before the fluid fully returns.