Control Arms? Anything else?

[relevante]

I've just gotten my new-to-me E93 out for a couple of drives as the weather improves and I've noticed that it tends to pull left under hard braking. Have been considering a sticky caliper as a possible issue, but it also felt possibly suspension related.

Looking closer at the car, the front left wheel has a lot of extra negative camber. It's visible just looking at it, and the camber pins haven't been touched.

Also, I can reach under and twist that left lower control arm pretty easily with one hand. The right one is a little harder but I can move it with one hand too. The car only has 43k miles, but it's still almost 16 years old. Checking the wheels for play, 12 and 6 feels solid but the left one has what feels to me like quite a bit of play grabbing at 9 and 3. The right wheel has some, but less than the left. TBH, I don't know what a brand new one would feel like here either though.

So I'm thinking I'll replace control arms, and while I'm doing it switch to the GAS monoballs (using their preinstalled setup) in the upper. Thoughts on that? Seems like a pretty likely cause for the pulling and/or camber issue, and should tighten up the play I'm feeling, right?

I'll replace all the locking nuts as shown in ISTA. Anything else I should do while I have things apart?

Thanks.

[MineralWhiteF80]

couple of items here to think about.

1. Before changing parts out and spending a lot of money, it might be a good idea to put the car on an alignment rack and see where you stand. It's possible the pulling is just part of needing an alignment. You can also simply swap the front tires left to right and see what happens to rule out a tire issue.

2. The lower control arms are able to twist like you are experiencing. That does not mean they are bad whatsoever. Over time, they can become easier to twist, but still in good working order.

3. Camber is not adjustable at all, so if you are certain both pins are still installed, you should not have a noticeable difference between left and right sides. That immediately makes me think something could be bent. Worn out thrust arm bushings will not change camber but it will change caster ever so slightly when deflected.

4. The thrust arm bushings will typically give you a shimmy in the steering wheel under initial medium to hard braking as the wheel/tire moves back and forth excessively. 43k miles on thrust arm bushings is really not a lot and I'd be very surprised if they are worn out unless you have hit a pot hole hard enough or have been driving the crap out of the car that has accelerated the wear. It is very easy to remove the one bolt/nut and drop the thrust arm down to inspect the bushing closely damage or cracking before buying 450 dollars worth of parts that may not fix it.

4. When is the last time you replaced the brake fluid and properly bled the system? If it has been over two years, it's a great idea to flush the brake fluid, properly bleed the lines and DSC (ABS) unit. You could also swap brake pads and see what happens.

[relevante]

Thanks for the ideas. All makes sense.

New info here though. I just went out for a semi-hard drive and came back to my shop and hit all the calipers with an IR thermometer. The front right was basically at ambient and the others were still over 100F. It appears that I have no front right brakes at the moment.

Am starting to research now, and will likely flush the fluid and take a look at the caliper first, but if anyone has any other ideas, let me know.

Thanks.

[relevante]

Tried flushing some fluid from the bleeder on the front right caliper and basically nothing. Front left was normal. Unhooked lines and have traced the blockage all the way back to the ABS module near the reservoir. Even with the line unhooked there, the pedal is firm and fluid just trickles out. Uh oh.

Going to try the whole flush procedure with INPA and hope for a miracle...

[relevante]

Also, to answer your question about when was the last flush: I just bought the car a couple months ago and have only driven it a few times, so this was going to be my first one. The service records show one at a dealer a bit over 3 years ago (only about 1500 miles since then). The fluid that I've gotten out so far looks pretty dark unfortunately. Kinda makes me wonder if it even got the full flush at that point.

[relevante]

OK, I think the INPA flush may be working that miracle. I'm getting some flow now!

[relevante]

Hmm, it worked for awhile, but after a short while driving, the front right brake stopped working again.

I’ll do more flushing when I get more fluid but any other ideas?

[MineralWhiteF80]

Originally Posted by relevante

Hmm, it worked for awhile, but after a short while driving, the front right brake stopped working again.

I’ll do more flushing when I get more fluid but any other ideas?

this sounds to have become more complicated

Assuming you are properly performing the brake fluid flush (I believe in you), it sounds like you could have a DSC (ABS) pump problem if you are only seeing results or changes in behavior after making INPA do the DSC bleed procedure

I would make sure you are doing the brake flush correctly using a power bleeder or the two person method, and the run the DSC bleed procedure a couple of times, and then see what happens.

and honestly, when I do the DSC bleed per ISTA+ procedure where it tells you to crack the caliper bleeder valve open and then pump the brakes 5 times, then close the bleeder valve, I have never had good pedal results after doing that. I run the DSC bleed, and then use a power bleeder to push the fluid though the lines.

[relevante]

Originally Posted by MineralWhiteF80

this sounds to have become more complicated

No doubt. Fortunately I *think* I have it fixed. I'm pretty sure there was just some junk in the ABS valves that had the path to the right front blocked.

After getting it cleared, I did a drive and it plugged again.

Then I just went nuts and flushed like a gallon of fluid through it, running the DSC routine on that wheel a bunch of times, and also flushed the others a couple times each. It actually plugged again in the middle of this, and then after another really difficult cycle through the procedure (brake pedal hard as a rock with the right front bleeder open) it passed a pretty big flake of debris. After that I didn't see any more particles in the fluid that passed and it kept flowing freely.

And then I did a normal bleed.

Haven't driven it a ton yet, but after a couple of short drives, all seems good.

Not that I didn't believe before, but a great demo of why you keep your brake fluid fresh!