88' F350 front brake issue

[Olds64]

You've never told us if it pulls only while braking. If it pulls driving down the road without the brakes on, it's suspension related.

You might go ahead and bleed the brakes to make sure each of your slave cylinders is getting good pressure. Rubber brake hoses have been known to fray internally and cause the brakes to grab and not release.

The master cylinder activation rod needs to be set if the vacuum booster or master cylinder is replaced. If it's too long this will cause your brakes to always be engaged. You'd probably see a weeping master cylinder if that was the case though.

 

[u2slow]

Have you ruled out a sloppy upper/lower kingpin? or TRE? If either of those can shift under braking, that wheel is going to steer itself slightly.

 

[clayhwalker]

It only pulls when I’m breaking. All the steering components are in good shape. And I highly doubt it’s the rod on my master cylinder since it’s been running fine for thousands of miles. Since I switched out the Hydro boost system

 

[ROCK HARVEY]

Does the pulling happen the first time you hit the brakes while driving, or does it take a few minutes to develop? I wonder if the left brakes are dragging and heating up to the point the brake fluid is boiling, so you get no braking on that side and the truck will pull to the right since that’s the only side doing the stopping. If it happens immediately when cold though, it must be something else.

What’s the condition of the hard brake lines?

 

[clayhwalker]

It happens immediately when driving. The hard lines are original to the truck but seem to be in good condition.

 

[u2slow]

It only pulls when I’m breaking. All the steering components are in good shape.

We already know the first part.
That doesnt rule out a worn kingpin shifting the steering axis or caster (on brake application) to make the rolling tire want to steer itself. Just saying its plausible... I had a worn balljoint do that kind of thing before.

 

[ihc1470]

So what are you missing? You have told us all the things that you have replaced with no changes which tells me you have over looked something. Sounds like something related to the left side brake. Have you followed the hard lines to see if any damage? Have you driven it a few miles and then stopped with out using the brakes if possible to see what temp the front brakes are at?

 

[Olds64]

What condition are the front brake hoses in? If they are OE it'd be a good idea to replace them and bleed the brakes.

 

[clayhwalker]

I tested the temperature with a temp gun and they were within 30° of each other after stopping. So I don’t think one’s locking up.

 

[scsmith42]

Here is the next step that I would take.

Drive the truck and apply the brakes, then pull it into your shop/garage/driveway and quickly jack up both sides of the front end.

Apply force to both tires with your hands with the goal of comparing the amount of resistance encountered between the two.

Presumably you will discover more resistance on the side that it's pulling to under braking. If this is the case, then I think that your problem could be one of several things.

1 - some debris entered the system when you were replacing the calipers - causing the pistons to stick in the caliper.
2 - faulty calipers
3 - calipers binding on the stainless steel pins.

I would further troubleshoot by removing both front tires, and trying to turn the rotors by hand w/o the wheels for leverage. It this also reveals excessive drag on one side, see the list above.

IF however, the resistance felt between the two sides is the same, then I would have someone help by getting inside the truck and lightly applying brake pressure while you turn the front wheels/tires by hand - again with the goal of comparing from side to side. What you're trying to do is have them apply say 20% braking and then freeze their foot into place so that the force applied to the brake pedal is constant, while you compare ease of rotating the rim/tires on each side. If you notice a delta between the sides, have them apply 40% braking, etc.

What you may discover is that the side that it's not pulling towards is not applying brake force at the same rate as the other side - indicating air in the system on that side or something causing the calipers to retract more extensively than the opposite side.

Bottom line is that it either comes down to a caliper dragging or one that is not engaging as quickly as the opposite side.