2004 LX470 Suspicious Brakes (1 Viewer)

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May 23, 2021
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Nigeria
So for the past few months (since circa February), the rear right (passenger side) tire has been giving me massive grief. Unbeknownst to me, two of the four clips (the ones that sit between the caliper and the brake pad) that hold the brake pad in place and prevent them from falling out when they wear down enough have been misplaced by mechanics and everytime the brake pads wear down significantly and fall away, the caliper piston pushes out of the caliper significantly and the rubber seal around the caliper piston starts letting fluid leak out.

I can't say I know exactly why this happens, but if someone could clarify what causes that rubber seal to fail, I'd appreciate that. Changing the seal stops the fluid from leaking out.

(just want to preface by saying that all parts bought were bought for both rear tires, but since the rear right tire is giving headache, I'll focus on that for clarity)
Anyway, cut to five days ago, the problem happens again. But this time there's a small twist. We took the car to the dealer to have those missing clips replaced, we also wanted to replace the brake disc (because it was cracked and chipped and really skinny), and put in new pads. Long story short, dealer messed up and bought the wrong disc and claimed that the clips didn't fit into the caliper "so they improvised." Mind you, I provided them with all the appropriate part numbers which I got using the vehicle's chassis number. Well, cut another long story short, dealer didn't do squat. They literally didn't fix anything and we left the dealer with the same problem: car was beeping like crazy and there was almost no braking power.

The next day, we go back to a "roadside" mechanic (the same one we've been going to everytime the problem happens) and he fixed the issue for now (turns out the "improvisation" from the dealer was to stick a piece of cloth between the pad and the caliper). Removed the caliper and its piston, washed them, replaced the seal, added hydraulic fluid and all was kind of well and good (also worth note that the pad hadn't even reached half of its wear and was fully seated so I have no clue why the piston seal failed, maybe the disc is just that skinny now or maybe it in fact fell out and the dealer put it back in place). The main difference here is that previously, when leaving the mechanic's shop, I'd usually have to drive about 1 mile or half a mile and the ABS and VSC and Brake faults on the dash would clear and normal braking pressure would return; however, this didn't happen. Let it also be noted that this time, the mechanic didn't bother spending time bleeding the brakes like we usually do, he also claimed that the dealer mechanics apparently attempted to "block off" the leaking caliper and had failed to properly do so.

Anyways, on account of the lack of braking pressure, I had to limp home and manually clear the codes via Techstream (something I had never done before) and braking pressure returned. The main problem and catalyst for this post is that, everytime I am coming to a stop from anywhere above 10 mph, the car sounds like it's a fricking jet engine shutting down. Literally a medium pitch loud humming that drops in pitch as the car slows, and sometimes, there's even a very loud and noticeable shuddering to boot. Also when accelerating, the humming sound goes from low-pitch to high pitch. I have noticed this humming sound before but it was never EVER this horrid. I have no clue where this humming is coming from, I think it might be from the front left tire but I don not know. I also think the shuddering might be coming from someone in the rear of the car.

My main questions here are:

1) What the hell is causing that humming and shuddering when nearing a complete stop?
2) What causes that caliper piston seal to leak when the piston comes out too far?
3) Why are dealer mechanics such a hassle to deal with?

Sorry for the essay.
 

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