Car pulling to left, gets worse when braking, often better when accelerating (especially when warm)

Question

I have a Ford Focus Mk1 (2004) stationcar edition. I've been fixing it up myself as a (very rewarding) learning project (my first), and I've recently changed the clutch after fighting the bell-housing on the clutch for a month or two. :)

I have one final problem with that car now.

It is pulling noticeably to the left and I constantly have to correct the steering wheel. When I brake, it get's slightly worse and spins the steering wheel a little if I let go while braking.

This problem wasn't there before changing the clutch. Note the car has been in a carport for a month on jack-stands so standing still it definitely has...

The weird thing is that it seems to fix itself almost completely when:

• The car has driven for a long period of time (100 km trip e.g.)
• If I accelerate, especially uphill and in a lower gear and high RPM (for max torque).

A quick Google reveals it's probably a stuck piston on the left hand side, and sure enough the pads were worn quite a bit on the inside vs. the outside. I reassembled the piston after compressing the piston (it was a little hard, but it was my first, so I have no reference), and re-lubricating everything to spec.

The problem got a little better but didn't go away. It has now come back somewhat over a week or two.

The thing is I'm running a little low on funds (all them tools for a starting DIY mechanic) and I would like to nail this problem first-try.

Google also tells me it could be everything from a bad balljoint (it fought me a little when re-assembling but has now play in the wheel now), a bad bearing (all wheels seems without clicking and play, very very slight on passenger-front), to the alignment itself being off (I find that plausible after the amount of violence required for the clutch job) and even the engine mounts themselves being damaged as the car straightens itself during pull.

The car has also been bought with 4 different tires and the threads are worn unevenly leading me to believe it had previous problems related to alignment or sticking calipers / dragging. I'm currently waiting for a tire machine to fix these. All tires are inflated equally in pairs to 2.4 front and 2.8 bar rear. I've matched the tires in pairs in relation to thread and rotation, and changing them around doesn't change the problem.

One of the basic checks for sticking calipers however, feeling for excessive heat doesn't really seem to hold true. I find that my calipers / wheel hubs in the front are either equally hot or cold. I hear no substantial noise or smell any weird smells around the car while off or driving.

The symptoms I'm having seem to indicate multiple problems or maybe just the one. I'm vouching for the left-hand caliper myself, but what are your well-educated and experienced opinions?

Answer 1

I've solved it. It was a combination of two problems.

The alignment was off by a few millimeters (don't know in degrees as I was using the string method). . I bought some really thin non-stretchy masonry cord in bright pink and put it up tight, and did it the "DIY Alignment way" as people suggests on Youtube. The left front wheel was toed out ever so slightly to the left when the steering wheel was locked in place straight ahead and the car had been rolled forward/backward a few times. I measured it on my 15" rims to be 2 mm difference from the front of the rim to the back, so 1 mm off on the toe-setting.

A note for this: Make the lines VERY long if you ever do it this way. Parallel them up, by measuring at both ends in front and at the back of the car. Align them around equally to the cars sides by eye. Now parallel them to the rear rims. Paint the places on the rims / cord where you measure from and to. Make sure it's always being measured at the same angles (90 degrees straight on). The sides don't have to be equal distance from rims to cord, but they do have to be absolutely parallel to less than <1mm. Now go check in front of the car and behind the car if the lines are still absolutely parallel to less than <1mm. This takes some time messing around. If you can get them all to match up, you have proven that the rear wheels are parallel to each other, and that you now have a parallel reference box around the car parallel to the rear wheels. This should be quite safe as a reference for a DIY toe-alignment for the frontend. If you can't get them to match up, you probably need a 4-wheel alignment and have to visit a guy with a laser-machine or try some other tricks... This worked for me. The key is patience, I've done this once before (where I apparently messed up) and this time it took me 3 hours. The adjustment of the toe setting is only like 5 minutes. The establishment of the reference points is where it's at. Remember to check the rims after adjusting all the way around, as well as the cord ends, that everything is still perfectly parallel or you can't trust your new adjustments at all.

The alignment bettered the problem a whole lot!!

AND the tires where different I stated so earlier in my question, but even through the thread looked approximately the same, and I've tried rotating the tires around, the different brands, times of being put on, wear and tear, plus sheer bad luck (and lack of experience probably) had me confused. Changing the rear tires to the front AND putting them on opposite sites against their rotational direction moved the problem to pulling to the right.

Putting on new tires and re-balancing them all on a static balancer made the problem go away. My car will now go straight down the highway with 130 km/h (80 mph) with no hands on the steering wheel (no worries, I keep them close).

Thanks for the suggestions. I'm glad I checked the pads though, because they had uneven wear on the left side as stated in my question, and now that I've aligned the car with new tires, I've been able to notice that even though it brakes straight, it shimmers the steering wheel while doing so, leading me to believe I'm dealing with one or two warped rotors.

Thanks again. <3