I have a '00 X with 50K and had a very scary experience on Friday. A traffic light changed just in front of me and I had to step on the brakes hard from about 50MPH. The truck shot left and starting hopping (enogh to scare those around me too). I checked all pads, calipers, rotors and all looks well. Posts show various suggestions from tie rods to rotors to replacing Calipers.
Can you share your experiences? This only occurs under heavy braking. Thanks

 

Had the same experience on my 04 excursion and they have replaced the front calipers on both sides, I think it has to do with sticking pins in the calipers. It corrected the pull I had but I still think they are suspect under panic stops

 

If you keep the slides lubed you should not have a problem. As long as I've been driving Fords they have had this problem, I guess I have gotten used to tearing into the slides and lubing them every six months or so. It would be nice not to have to do this but I also get a good look at the brakes and the rest of the steering and suspension at the same time. In the long run it has saved money and down time on the trail.

Be safe. Toyman

 

Mine is pulling real bad to the left, is this the only problem it could be.

 

What kind of lube would you use for the sliders? Assume the sliders are the bolts holding the calibers together that allow movement? What about the clips that hold the pads in, would you lube here to. My fear is that lube would cause dirt to stick and actualy do more harm?

Educate me...?

 

I have done the good-o search thing......came up with 207 hits and not a one had anything other than what is here.............bummer.
HELP

 

There can be mechanical issues with the suspension that can lead to pulls, such as worn ball joints or tie rod ends.

The foundation brake can also be at issue. First, one has to realize all friction materials have a variable coefficient of friction or mue based on the temperature and conditioning they experience. Especially semi-metallics. the other is that our vehicles have a large scrub radius, meaning the centerline of the tire to the centerline of the balljoints is large, so just like a cheater bar with a socket wrench, there is a lit of leverage. Small changes make big changes.

There are areas of the caliper to look at. One is the slide pins of dirt and corrosion, which should be looked at every spring due to the design of this vehicle. Another issue is the fitment between the pads and torque brackets. The ends of the pad steelbacks can wear away the paint and form rust, which then keeps the pads from freely retracting. Since cleaning with a wire brush and a light coating of grease helps here.

The caliper pistons can also hang up due to dirt corrosion, or heat deterioration of the O-rings, preventing roll back. This is not that common. Another area is the brake hose which can develop internal tears and act as a one way valve, but this is generally noted during all brake applications.

Any hangup of the pins or pad ends can lead to less then ideal cooling of the pads on one side of the axle. This will turn into a pull due to as little as 100°F differential side to side as demonstrated in this and the next pictures.

Pictures and details of the pins can be found here.

 

This is great stuff, my problem.......the truck only has 6491.2 miles on it. Tires are kept within .2 tenths of psi
Taken care of extremely well, changed oil twice already.
Any more ideas, or help would be greatly appreciated

 

Tim,

If you looked at the graphs of city traffic with the temperature spread and brake pull, that was with new calipers, rotors and pads for a test. The pull started on day 2, which runs 200 to 400 miles for the 10 day test. So it can happen quickly.

Has it done this right from the start, and how often do you drive it?

 

It has never done it! I only drive it when I pull the trailer, see gallery. Bought the truck new in September of 03.
After reading your posts and studying the graph, decided to take the truck out.
It did not do it at all, did some panic stops and absolutely nothing…..ug…
When it did, it was coming back in town from a 590 mile trip. It could only be the heat………..I hope. Funny thing I had climbed a long hill and did not even use the brakes. However, I know the crown of the road will load the left front constantly………………so….

 

You won't have to be using the brakes.

If a slide pin sticks a little, or a pad hangs up in the torque bracket, the pad will not fully retract and stay in partial contact with the rotor, specifically the highest axial runout of the rotor (probably 0.0010"). This is not enough contact to develop a drag, but it keeps that pad at a little higher temperature then the pads on the other wheel. In some situations of long drives it can be generating heat, and therefore hotter. In other situations with some occasional brake applications, it's more of a matter of not cooling as well. The start, 10:30 and 2:30 sections of the referenced graphs are periods when the driver is making brake applications every mile.

You only need about 100°F imbalance between the two wheels for a semi-metallic to develop a pull on many vehicles, especially this one. The coefficient of friction of a pad changes with temperature, more then the edge code on the pad would indicate.

In this situation, you can go out with cold brakes and do several stops in a row and generate up to 1,000°F and never experience a pull. That's because while your generating balanced heat during every stop. Your not duplicating either the dwell cooling periods, or the long drag that can heat up one pad or pads at one wheel.

This situation may go away if there is just a minor hangup and some additional stops clear the issue. The normal dealer response to a pull is to install new pads and turn the rotor to freshen the surface. Not a good move, especially if slide pin is starting to hang. But sometimes just moving them solves the problem!

Go back to the day 3 graph. Pads were switched from left brake to right brake. If the issue was a poorly processed and inconsistent set of pads, the temp would have gone to the right. But it evened out and the vehicle continued the test without any more pulls just by moving the calipers during the pad swap. The test did have slightly higher left brake outer pad wear. If you look closely at day 3, you can see in a few places where the left pad temp slightly exceeded the right, but the right never did the same. There was still some hangup.

Here is the other problem with this. You have one pad that is touching a high spot on the rotor. Over time, this region will wear down develop a thinner region in the rotor. Usually the rotor will have a region on the outer surface that has a high runout, and a different one on the inner rubbing surface. If one or both of these abrade to the point of having 0.0006" wear you will develop pulsation, what mechanics for years have improperly blamed on warpage.

So before you get to that point, it would be a good idea to check for pad and slide pin freedom.

Edit - The crown of the road may be loading the tire, but the brake does not know how much weight is over it. It's just going to disipate energy at whatever clamping force the hydraulics force it to do.

Jack

 

Jack.....

From an engineering point of view and thermodynamics, this is great stuff.
I have learned a ton from you…….and for that my friend a tremendous thank you.
I will pull the front wheels and check for freedom with the pins.

A footnote to all this. Hang around you expertise, and methodology to problem solving is what FTE is all about. Helping…….you defiantly have the skill set and use of the English language to help many.

Again thank you

 

Tim,

Glad to help and share. Brakes are not rocket science, but the attention to detail gets lost in the field.

Having an 03, you are at the transition point where pads were changed from a traditional noise insulator to what is known as double stick. The double stick have a silicone adhesive backing that adheres the pads to the pistons and caliper fingers for additional noise suppression. It's not what I thought should have been done with this caliper since the slides and pads can need maintenance since you have to break the insulator bond to remove the caliper from the wheel.

So if you do have the double stick and the caliper will not slide easily off the pads, you can go though an alternate path to accomplish the same thing.

For the pins, the easiest thing to do is to remove the pin retention bolts (you can do one at a time), then just push the pins in and out between the bracket and caliper , then twist them to get some of the lube to redistribute. But first check the top pin boot for tears or burns, and sometimes displacement off of the retaining grooves. The reason the top boot is more prone to issues if that hot friction material debris get thrown into it during braking. If your dissipating a lot of energy (speed and load), they have been known to have an issue.

With the pin bolts reinstalled and torqued to 42 lb-ft, try to push the caliper away from the vehicle so the pistons are pushed in. This is a pain in the tail and we made up a bracket to facilitate this, but if I remember correctly, the guys were able to pry between the existing torque bracket and caliper being careful. This will give clearance between the pads and rotor so you can slide the caliper and adhered pads back and forth to insure the pads are not stuck and broken free (if they are hanging). Just remember to apply the brake and bring everything back together before you drive off.

If the pads do not have the double stick insulator, it's much easier. First remove the top pin bolt only, then swing the caliper towards the back of the vehicle on the bottom pin. It's bes to have a bungee cord available so the hose does not take the full responsibility for holding the caliper in position. this will give full access to the top pin and pads. The V-Springs on the tops of the pads are there to push the pads away from the rotor to prevent the rotor wear, which will develop into DTV (disc thickness variation or out of parallel surfaces). If the pads are moving freely, when you open the caliper the springs should move the pistons out of place. Vehicles with a lot of corrosion on the ends of the pads can require prying to get the pads out.

With the V-Springs removed, and possibly the pads, I bring the caliper back into place, reinstall the top bolt and remove the lower bolt. Then lift the caliper a little so I can work with the lower pin. When the lower pin is addressed, it gets bolted back together and I go back to where I was, removing the top pin bolt and swinging the caliper pin open. I go through all of this as I try not to remove the caliper entirely and chance it falling and tugging on the brake hose which with the weight of these calipers will cause an internal hose lining tear.

If there is pad hangup, the ends of the steelbacks need to be wire brushed clean and a light amount of grease applied. Sometimes the stainless steel slippers need to be removed and the bracket wire brushed as well. But this is usually only on a high mileage, well exposed vehicle. When it's back together, the re-installation of the V-Springs gets tricky, and here is where they get tossed by some mechanics.

The V-Springs will push the pads out and make it hard to get the caliper back on, although using the swing method is much easier. For the passengers side, I use my right hand to hold the pads together and springs down on the top of the pads while I swing the caliper back down. As you pull your right hand out, the one V-Spring tends to get hung up on the caliper, and you have to reach in one of the holes in the caliper bridge and push the spring down, then the caliper will fully move into place. When installing the pin bolts back in place, make sure that the flat area of the pin fits correctly into the caliper, and make sure that the ends of the boots are still retained in their grooves in the bracket and pin.

Repeat for drivers side.

Torquing the wheel lug nuts. Improperly torquing the wheels in tightness or pattern can cause stress distortions with any vehicle. The best practice is to tighten in increments and following a cross pattern. With a torque wrench, I use steps of 80 lb-ft for all 8, then 120 for all 8, and finally 165 lb-ft. And recheck after about 500 miles to make sure they did not back off. Nothing like having your wheel pass you while driving down the road.

I wrote this much detail for others, as I believe you are just going to have to move things around a little to get something freed and re-greased at your mileage.

 

Your detail is remarkable…………shows……..one who thinks!
What is you advice on grease, best possible; I do not care about cost.
I care about my truck and doing what is best.
I have, over time, created quiet a collection of great info for my own Ford Truck Book. (FTB)
You instructions have earned a front row spot!!

 

Thanks Tim, but it's what I do in life. I probably missed about half of what I should have told you as I'm not in the 99-04 frame of mind anymore. As I looked at the pictures for the response below, I remembered that the guys used to use a large c clamp to pull the pistons in, using it between the end of the slide pin bolts and outside area of the torque bracket for the double stick insulators.

For the slide pins, the Ford silicone caliper grease is a good product and easily available, and what we use in the workshop. It's not the same product that is used by Akebono who manufacturers the calipers, but it is good. considering how many trucks have had pin issues, I'm glad it's not the same. But the boots are the main weak point here.

You need to use silicone because the rubber boots will not tolerate a petroleum based products as shown here.

The pad ends are another story, and I prefer using assembly lube with moly, as the moly works best with sliding surfaces. Any parts source would be good.

Jack