Heated frozen brake pucks -- Uh Oh

WellWell · Dec 10, 2024

Not a newbie to wrenchin stuff, but this is a 1st .

The throttle side brake pucks were frozen and a sonic clean did not free the stuck gunk.

Used a propane torch and penetrant to free things up and eventually this worked to remove the puck.

The removed puck turned super dark brown and does not polish out. Looking for experienced wrenches who can weigh in on what happened here. Here is a pict of the heated frozen throttle side puck next to the caliper just pulled from the sonic cleaner. This doesn't look right.

Experienced wrenches, what can you tell?

Thanks
WW

RossKean · Dec 10, 2024

I think the brown color for one of the two piston pairs on the right side is normal.

EDIT: You should note that the lower piston pair on the right hand caliper is NOT actuated by the front brake lever - it is ONLY connected to the rear brake pedal. (Linked braking system)

Whooshka · Dec 10, 2024

That stuck gunk looks like the piston seals. You're gonna have to do a complete rebuild.

I'd avoid using a sonic cleaner on calipers in the future. It's why they invented brake cleaner.

RossKean · Dec 10, 2024

Whooshka said:
That stuck gunk looks like the piston seals. You're gonna have to do a complete rebuild.

I'd avoid using a sonic cleaner on calipers in the future. It's why they invented brake cleaner.

Yes, the piston seals on the assembled caliper are definitely chewed up. Looks like corrosion on the pistons as well. If not deep, the corrosion may be able to be polished out. Otherwise, they'll chew up your new seals and leak.

Dan Cooper · Dec 10, 2024

You guys do know WellWell is talking about the BLACK piston that is above the caliper in the photo, don't you???

dan

RossKean · Dec 10, 2024

Dan Cooper said:
You guys do know WellWell is talking about the BLACK piston that is above the caliper in the photo, don't you???

dan

Yes. Seems to me that one of the piston pairs in the right caliper normally is a different (darker) color - the piston shown separately. The complete caliper below shows seals that are buggered up and what appears to be corrosion on the side of the piston.

Dan Cooper · Dec 10, 2024

You guys do know WellWell is NOT asking about the complete caliper, don't you??
You do know that avoiding the question being asked is not particularly helpful, don't you??
You do get that he is most likely in the process of disassembling the calipers for service, eh??

dan

Panman · Dec 10, 2024

Dan Cooper said:
You guys do know WellWell is NOT asking about the complete caliper, don't you??
You do know that avoiding the question being asked is not particularly helpful, don't you??
You do get that he is most likely in the process of disassembling the calipers for service, eh??

dan

You seem a bit condescending. Kind of like a wife. Note to myself avoid Dan Cooper!

2GENAE · Dec 11, 2024

Panman said:
You seem a bit condescending. Kind of like a wife. Note to myself avoid Dan Cooper!

That would be a mistake Dan has 20 years experience with FJR1300 maintenance. But you do what you think is best good luck in the future. So far noone has addressed that black piston..

Whooshka · Dec 11, 2024

OK so I'm guessing that black puck was not black until it was hit with penetrant and a propane torch. I don't know what the pucks are made of and I'm no metallurgist, but I do know heat will discolor stainless steel. Not blacken it but give a multicolored/rainbow appearance.

I'm also guessing if the puck was in the caliper when the torch hit it would only the exposed portion turn black? Maybe it's an aftermarket puck?

Next time if you need to remove the pucks do it with the caliper still mounted and use the hydraulic pressure of the brake system or remove the caliper and use compressed air.

Whooshka · Dec 11, 2024

Dan Cooper said:
You guys do know WellWell is NOT asking about the complete caliper, don't you??
You do know that avoiding the question being asked is not particularly helpful, don't you??
You do get that he is most likely in the process of disassembling the calipers for service, eh??

dan

Any related info may be helpful. Chastising us for not directly answering the OP's question isn't particularly helpful either.

2GENAE · Dec 11, 2024

Whooshka said:
Any related info may be helpful. Chastising us for not directly answering the OP's question isn't particularly helpful either.

Ive known Dan for almost 4 decades he was not "Chastising" but pointing out what the OP was asking with no direct answer. You did make a good point removing the pistons with hydraulics while still mounted.

IMHO it was helpful, some of these posts get of topic so fast . No disrespect meant Whooshka.
Louis

metalman · Dec 11, 2024

Most steels will turn a very dark blue when heated to around 575 degrees…..which the original poster did.

RossKean · Dec 11, 2024

I mentioned (twice) that according to my recollection, one of the piston pairs in the right front is a distinctly different color from all the others - from the factory. I believe that this is the black (or dark brown) one that is at the top of the photo. I never had them out but I do extend them for cleaning when I change pads. The discoloration seems far too uniform to be the result of heating with a propane torch or contact with brake cleaner or other chemical. I don't have a supporting photo but clearly remember a different color on my Gen II. (Perhaps I am mistaken???)

My other comments related to the still-assembled caliper where the seals are definitely messed up and at least the top left piston pair is significantly corroded. (I realize that wasn't the original question.)
Also noted that the apparently "stuck" pistons might have been the lower right pair which would not be pushed out using hydraulic pressure from the hand lever as this is the "linked" piston actuated using the rear brake only.

Whooshka · Dec 11, 2024

2GENAE said:
Ive known Dan for almost 4 decades he was not "Chastising" but pointing out what the OP was asking with no direct answer. You did make a good point removing the pistons with hydraulics while still mounted.

IMHO it was helpful, some of these posts get of topic so fast . No disrespect meant Whooshka.
Louis

No offense taken. Dan is incredibly knowledgeable and I've taken his advice often. He doesn't hesitate to help anyone and has my utmost respect. Chastising probably wasn't the right word to use.

I just think his comment wasn't really needed as almost every thread goes off on a tangent at any given point. Maybe he or I just woke a little grumpy that day.

RossKean · Dec 11, 2024

Good video on rebuilding front brake calipers

Note removal of the smaller of the two piston pairs on the right front starting around 15:15. Piston looks quite a bit darker although not cleaned - hard to tell for sure.

Edit: Maybe both piston pairs on the right caliper...

torch · Dec 12, 2024

I would recommend measuring the bores in the caliper for diameter and parallelism very carefully after subjecting them to that kind of heat. It would be a shame to spend a lot of time and money rebuilding them only to find they were warped and/or distorted.

Prosolar · Dec 12, 2024

Where did wellwell go? I think that dark piston is it's natural color. And the other pistons look a little dirty is all probably not corroded... I doubt if he's using penetrating fluid with the torch he got it hot enough to warp anything.

RossKean · Dec 12, 2024

Prosolar said:
Where did wellwell go? I think that dark piston is it's natural color. And the other pistons look a little dirty is all probably not corroded... I doubt if he's using penetrating fluid with the torch he got it hot enough to warp anything.

I agree about the natural color. My comment on the corrosion is based on what I see mostly on the top left piston of the assembled caliper. Could probably be polished out.

torch · Dec 13, 2024

Prosolar said:
I doubt if he's using penetrating fluid with the torch he got it hot enough to warp anything.

I'm not saying he did, but:

WellWell said:
Used a propane torch and penetrant to free things up and eventually this worked to remove the puck.

Compared to using an oxy-acetelyne torch, the propane has overall lower heat and is therefore less likely to cause localized damage directly. However, aluminium dissipates heat throughout the casting rapidly and the uncontrolled nature of hand-held heat application certainly has the potential to act on or introduce internal stresses that could distort the casting.

If it was my braking system, I would be verifying things with precision measurements. Your brakes, your call.

Heated frozen brake pucks -- Uh Oh

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