First the bushings for the lower control arm / ball joint and the strut rod should be inspected. If they are deteriorated they will let the alignment shift between braking and accelerating.
You need to understand too that we used to call these and the older Escorts "killer cars" because of the huge number of crashes due to separating ball joints and tie rod ends. I'm not happy you've spent a lot of money on this problem but I AM happy it has been inspected numerous times. I think we can rule out the common safety-related stuff.
There's two other things I can think of to look at. First of all, one of my reasons for being cynical is Ford was too cheap to provide alignment adjustments for "caster" and "camber". Caster is not a big tire wear angle and is no longer adjustable on about 95 percent of front-wheel-drive cars, ... And it doesn't really need to be set as precisely as on older cars. Camber, on the other hand, is a sad story. That is the inward or outward tilt of the wheels as viewed from in front of the car. Perfectly straight up and down is 0.00 degrees. If you can imagine a wheel laying on it's side, that would be 90 degrees. The typical camber specification for any car is commonly around 0.25 to 0.75 degrees. That is done for a compromise of the best tire wear, best ride quality, and to place the vehicle's weight on a certain part of the wheel bearings. With anything over about 1.00 degrees, the tires will start to wear excessively on the outer edges. The earliest Escorts and Tempos called for a camber reading of 2 11/16 degrees! This resulted in front tires lasting about 15,000 miles but the salesmen didn't want you to know that. The cars rode much smoother than competitors' models on a test-drive, so they sold a pile of them.
Ford couldn't be bothered to provide a camber adjustment, and due to the design of the struts, there is no way to correct this design problem. Also, to make up for a constant pull to the right, left camber was made considerably higher than the right side at the factory. (Tires want to roll in the direction they're leaning so camber is normally adjusted so both sides are basically equal). Those two measurements can not be changed by your alignment mechanic. What you got is what you get; tire wear and all. The only thing he can change is "toe" on both wheels. That is the direction the wheels are steering when the steering wheel is perfectly straight. "Total toe" is simply the addition of the toe readings on both wheels. Today all cars call for just a fuzz "toe-in". That means the fronts of the wheels are about 1/16" closer together than the rears. Road forces and braking forces tug the wheels back and make them perfectly parallel. There were a lot of Ford front-wheel-drive cars that called for "toe-out" with the idea that the cars pulled so hard going down the road that the engine would tug the wheels forward and make them parallel. That was the setting that gave the least amount of tire wear. What can happen now, especially since tires are always improving and have less rolling resistance, is your wheels may still be toed out on the highway. That means each one is steering away from the center of the car. The car can only follow one of the tires and that is going to be the one with the most weight on it. That is the right one because roads lean to the right so rain will run off. Braking can aggravate that pull, but it takes a keen observer to determine whether the pull you're experiencing is due to the alignment, SHIFTING alignment, or some other unrelated cause. If you have a printout of the alignment, I would like to know the numbers for both front wheels for camber, toe, and "SAI, (steering axis inclination). With those I can start to make an educated guess if something obvious is wrong. Negative toe numbers means toe out. Negative camber numbers means that wheel is tipped in on top. Positive camber is normal.
Keep in mind too that if the pull is due to an alignment issue, there would be at least a hint of a right-hand pull when you are just cruising at a steady highway speed.
The next thing to look at is brake pad wear. It may be too soon to tell with your new pads, but there is a real common problem on GM front-wheel-drive cars with a pretty easy fix, and after doing brake work for well over 30 years, I have never run into this on any other car brand until about two months ago on this forum while helping someone with another Tempo. I still find it hard to believe I've never run into it before, but what happens on the GM cars is there is a valve inside the master cylinder that trips when there are unequal pressures in the two hydraulic circuits when you press the brake pedal. That tripped valve blocks fluid flow to one front brake AND the opposite rear brake. No matter how hard you try, you will not get any fluid to flow out of one of the front caliper's bleeder screw and one rear wheel cylinder's bleeder screw. There's two clues to look for on GMs. The first is a complaint of the pads wearing out much too quickly on one front brake and the other side looks like new. That's because one side isn't applying at all. By the second or third new set of pads people finally realize there's something wrong that needs further attention.
The second clue is a subtle one. Watch the steering wheel when the brakes are applied lightly. You'll see it wobble just a little to one side, then come back to center while the car steers to the side too. It's not nearly enough to lose control but it is noticeable. Most front-wheel-drive cars use this "split-diagonal" hydraulic system because 80 percent of the vehicle's weight is on the front tires so they have to do the most stopping. To prevent a loss of that 80 percent of your braking ability in the event of a leak, with the split-diagonal system you will always have one front brake working. On older rear-wheel-drive cars if you only had one front brake, it would tear the steering wheel out of your hand when you applied that one brake. I've driven cars that I cobbled like that, and it's no fun.
To address that hard brake pull with the split-diagonal systems the manufacturers have changed the geometry of the suspension system. In particular, "scrub radius" is the angle of importance. It can not be measured or adjusted. The RESULT of scrub radius is the left half of the tire tread wants to tug the whole tire to the left due to road friction, and the right half wants to tug the whole tire to the right. The scrub radius angle is formed by drawing an imaginary line through the lower ball joint and the upper ball joint, or in your case the upper strut mount. Those are the two steering pivots for the wheel. That line intersects the road surface exactly in the center of the tire tread. That point was moved way off-center on rear-wheel-drive cars. Chrysler is the only manufacturer that has that so fine tuned that you will not see that little wobble in the steering wheel, and you may not even know you have a problem if it wouldn't be for the red "Brake" warning light and the low and mushy brake pedal. I've had more than my share of metal brake lines rust out and cause a sudden unexpected leak, and it was impossible to tell which brake was affected by driving the vehicle.
As a side note, altering the ride height of a car or truck, installing tires with a different circumference, and installing wheels with a different offset all change scrub radius and WILL adversely affect braking and handling. Lawyers and insurance investigators love to find those kinds of modifications. They will convince a jury you were partly at fault for the crash when the other guy ran the red light because you were less able to avoid the crash, ... And they will be right.
Sorry for getting so far off track. What you should try is a hard stop on sand or snow to see if both front wheels lock up and skid. You can do this in a driveway. If one wheel doesn't skid, you likely have that valve tripped in the master cylinder. As I mentioned, in all my years as a brake and alignment specialist, I've seen this many times on GM cars but never on any other brand. I ran into it once with one other person on this site and the solution for GM cars worked for him. You need to go to one of the wheels that isn't flowing any brake fluid, open the bleeder screw, and give it a quick, short burst of compressed air, then let it gravity-bleed for a minute. You want to avoid blowing air all the way up the line to the master cylinder because you'll just have to bleed it all out again. It's sufficient to blow the brake fluid back 6" to 10" in the line. That's enough to unseat that valve.
Tripping that valve can be avoided by never pushing the brake pedal more than half way to the floor. That is an important rule for any car with a master cylinder more than about a year old. The lip seals can be torn on the crud and corrosion that build up in the bottoms of the bores where they don't normally travel. Some people will tell you it's important to bleed all four wheels in a specific order but that will not prevent the problem if you push the pedal too far. Besides a leak, that valve can also be tripped by not being aware of what it takes to trip it. When any brake work is done involving new pads and / or calipers, the pistons have to be pumped out until they contact the pads. On one side the piston will always come out first and that circuit will start to build fluid pressure, THEN the other side will start to move. If the pedal is pushed far enough, that can trip the valve. Pedal-bleeding with a helper is another problem. Once the pedal is pumped up and some pressure is developed, opening a bleeder screw causes a loss of pressure in that half of the system, and the valve trips. I only do gravity-bleeding with no helper.
There's a whole bunch of ideas. I suspect your control arm and strut rod bushings have been inspected already. If not, don't overlook them. Check for an inoperative front brake. On the GM cars, you can still turn the wheel by hand while a helper pushes the brake pedal to make the other side lock up. I don't know if it is just as obvious on your car.
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Saturday, February 23rd, 2013 AT 1:29 AM
