brake caliper and bracket corrosion

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brake caliper and bracket corrosion

Post by ihaveavibe » Sun Apr 15, 2018 2:01 pm

About two weeks ago I replaced the brake caliper and bracket (plus pads and rotors, but that's not important here) with a shiny new remanufactured one. I was under the car the other day and noticed they had already started corroding. Is this normal?
I realize there is brake dust down there... could it be due to leaking brake fluid (I initially had not tightened the banjo bolt enough which i realized while bleeding the system, and that might be the source of the deep orange corrosion in the photo)? My reservoir seems to be topped up. Or perhaps it's just normal? Just wondering...
caliper corrosion - small.jpg
caliper corrosion - small.jpg (171.1 KiB) Viewed 487 times

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Re: brake caliper and bracket corrosion

Post by ColonelPanic » Sun Apr 15, 2018 4:57 pm

Probably "normal," for better or worse. We had a seized caliper on ours several years back and the shop replaced both with re-manufactured... They too ended up looking like that in no time. When it was time for the next brake job, here's what it looked like:
old1.jpg (110.29 KiB) Viewed 482 times
From what I understand, the OEM calipers have a coating that's supposed to prevent corrosion, but re-manufactured calipers may not have the coating. I really don't care for the looks of it, but allegedly the corrosion is "cosmetic."

The piston in the caliper pictured above would not compress when I went to replace the pads, so it was time for new calipers again. I replaced them with a pair of Centric Posi-Quiet loaded calipers which have a nice gold coating on them. 8-)

Before it gets too bad, you could probably clean up what rust has already formed and paint 'em.
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Re: brake caliper and bracket corrosion

Post by jolt » Sun Apr 15, 2018 10:24 pm

Brake fluid can destroy paint, cause it to blister and peel. It looks like the caliper was painted by the marks left from the brake fluid running down the caliper. Read the brake fluid bottle and it will tell you these things. I hope you did not get ant fluid on other painted surfaces. It was going to get rusty eventually. The brake fluid just sped up the process.

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Re: brake caliper and bracket corrosion

Post by ihaveavibe » Mon Apr 16, 2018 8:40 pm

Thanks. The ones I replaced were far more corroded. I realize brake fluid removes paint... but it dripped down, not up, and I wiped it... so I was surprised it was already so rusty. I guess I'll torque that bolt a little more just to be sure, even though I thought I did it to spec.

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Re: brake caliper and bracket corrosion

Post by SeattleJeremy » Tue Apr 17, 2018 3:37 pm

It's possible fluid you wiped up compromised the paints integrity, and it failed, then little by little all of it flaked off, due to the corrosion underneath. If the caliper is in good working order you might want to remove it, clean it up with a wire wheel, and put a good coat of caliper paint on it.
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Re: brake caliper and bracket corrosion

Post by Derf » Sat Apr 21, 2018 5:25 am

A lot of aftermarket replacement parts come with a light corrosion inhibitor, which is easily washed off under normal use (sort of like spraying non stick cooking oil in a pan before cooking an egg). This makes the part cheaper, the downside the part starts rusting almost immediately. If the replacement part is near visible part of the car it can cause its cancer to stain locations you are trying to keep clean. Since most aftermarket parts require a core exchange, their is often no chance to get the part a ahead of time to apply a proper rust preventive coating. In the case of brake calipers it is considered normal, but messy.
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Re: brake caliper and bracket corrosion

Post by ihaveavibe » Thu May 03, 2018 10:52 am

Thanks for all the replies. There was one thing that might have added to the corrosion that I hadn't considered, which is seepage from the bleeder screw.

I've been keeping an eye on this brake job and decided there might be some brake drag and ultimately decided to bite the bullet and changed the hose. This time I really torqued the banjo bolt and still saw some fresh looking liquid from above, so I also extra tightened the bleeder screw. Does anyone know what the torque spec is? I was worried about stripping the thread or rounding it off. Thx

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Re: brake caliper and bracket corrosion

Post by vibrologist » Thu May 03, 2018 12:01 pm

Torque specs of bleeder screws is a topic that arises quite often. I have never come across a number on any brake video I saw.

Here is a something I found on a Miata forum: "I don't know of a spec for it, but based on these bleeder inserts being low hardness steel and the caliper being cast iron, you are talking in the range of 30 ft-oz or so (not ft lbs)

The normal way used to specify a close torque of a seated valve like this is along the lines of "turn until seated and then another 1/8 to 1/4 turn to tighten". That is what I would recommend."

If your bleeder keeps leaking it has been deformed by too much force. In that case I would replace the bleeder with another one from the junk yard.
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