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2012 E550 Coupe Brake Inspect

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Old 08-02-2021, 11:25 AM
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E550 Coupe
2012 E550 Coupe Brake Inspect

New pads and rotors were installed all around by PO last fall. There is a slight squeal that appears from passenger front wheel after about 10 minutes of driving, and only when the car is driving straight, with very slight pressure on the steering wheel to the right (so the steering wheel is not floating, if that makes any sense). If the steering is turned either way, or brakes even slightly applied, makes the squeal disappear. And it also comes and goes on its own. Sure hoping its a loose pad, and not a bearing, but I know from experience all things are pointing to wheel bearing... But this one is wierd since its so random when it comes and goes.

So anyhow, I've only had the car for a few weeks now and thought it would be good to go through the brakes and clean them up. I try to do this in the spring and fall, when swapping winter / summer tires over.

I found the process pretty straightforward, and didnt run into too much trouble. Man the brake hoses are tight when taking the caliper off! They did not leave too much slack to get them off. Pads were in good shape, just needed the contact points cleaned up. Also took the rotors off and cleaned up the back sides, applied a bit of anti-sieze between the rotor and hub.

One thing I also encountered - the bottom caliper pins are very tight in the caliper sleeve! I was able to wrestle the passenger side out by hand, but the drivers side was extremely tight. I had to press it out with a make-shift pin press, excuse my backyard cludginess but it did the trick! After cleaning the sleeve and the pin (lots of dried up lube and gunk on them), and a bit of new lube, they slid in perfectly.



Now to get out for a drive to see if it made any difference with the squeal. I'm not holding my breath lol.
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Siegmann (08-03-2021)
Old 08-10-2021, 09:33 AM
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E550 Coupe
Front end squeal - 8 day followup

Its been a little over a week since I cleaned up the brakes, in effort to fix an intermittent squeal that sounded to be coming from the front passenger wheel. After putting everything together and taking a 10 minute drive with a half dozen stops, no noise. After many trips like this over the last week, in different conditions of hot, cool, wet and dry weather, still no noise! Time will tell if it comes back, but things are looking better each day that its not a bearing.

I suspect the very tight lower caliper pins were preventing the caliper from pulling away from the rotor after applying the brakes under certain conditions. Cleaning them up helped them move freely, allowing the anti-rattle clip to do its job. I'll post an update if it comes back or if there's anything noteworthy.
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Siegmann (08-10-2021)
Old 11-29-2021, 05:48 PM
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Front end squeal - 4 month followup

Over the last few weeks, the squeal came back. All the same symptoms as experienced in August. I got it into the shop this weekend and inspected the brakes. Sure enough, the lower caliper pins were very tight again. I had bought a front pin boot kit to replace the old ones (Carlson 16156). The top pin boots are all rubber, so fairly easy to replace. The lower originals have a plastic bushing molded into the rubber, and they would not budge. I very carefully cut through the inner plastic part of the bushing with a hacksaw blade, then chipped it out with a small punch. The pin bores were cleaned up with a pencil grinder and a wire wheel attachment. Installed the new boots with brake grease on the outer surface to get it to slip into place.

The caliper pins now glide very easily as they should. I'm hoping this is my last update on this issue, but will repost if anything changes.

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