Rusted caliper piston

cobrasneverdie

cobrasneverdie

el guapo
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Hey guys, just looking for suggestions/opinions on the matter at hand. So I took my front brake apart, it hasn't been used in a long time and this is what I saw.
zlHpHMN.jpg


The thing is quite rusted, I cleaned out some of it and picked out some rust out, however it is not coming out. Any suggestions from here, should I buy new calipers or is there a way to take these out and salvage this? I think I read somewhere you can take an air hose and blow it out?
I'm still new and my bike is at my friends place so I'm limited to tools
 
Use a grease gun on the bleed screw with it open and it should push them out. I'd probably soak them with some penetrating fluid first. Looking pretty crusty.
 
Just warmed up oil same as you use in a diesel car,I dont hold out much hope really. I f that doesnt work I will try welding a bolt onto the piston and get a spanner on it ,thats a last resort as it will ruin the piston.
 
Hey yellowdog:

Ok say I do end up going that route, if it happens to come out... What are the chances that the new piston will fit in there with all that rust in the inner caliper? Will I have problems with a new piston and it's rusted inner part. Just curious to know
 
I have gotten unbelievably rusted and stuck pistons out by using the grease gun method that has been mentioned. Replace the bleed screw with a Zerk fitting. Then I put the stuck caliper in a pot of boiling water for 15 minutes. That's the real secret, getting the metals to expand, and the aluminum body will expand more than the steel piston.
Once out, the piston will probably have to be replaced, but the bore will probably be okay. Just clean the bore with a gray Scotch-Brite pad.
 
bolt the two halves together but flipped to seal the fluid connection that lets you c-clamp whichever piston moves first so they both can be forced out. I agree heat like from a hair dryer and a grease gun. Saw the "bolt together flipped" trick on here, sheer genius.
Grease gun won't send the piston through the wall of your shop like air can.
 
That is pretty damn quick thinking on the bolt together. Never really thought of tossing them in boiling water either. The linear expansion for aluminum at 100 C is greater than that of steel, which is stable to a much higher temp, so the boiling water should work great. I did wonder about Gary's crock pot though! Might be an idea too, if it's not full of carbs!
 
Cant say what state the caliper will be in after or when the pistons come out as I cant get them out.! reading on here it seems a very light sanding will restore them.
Just wondering if it is actually rust thats making them stick as the pistons are stainless and the calipers are aluminium so that equals no rust,or are the calipres cast iron ?
If the boil in oil doesnt work I will try the grease gun.
 
The stock pistons are chromed steel not stainless, Mike's replacement pistons are stainless.
I have a spare M/c that I use to push out the pistons. This way you only put something In there that is supposed to be in there. I don't like the grease gun idea.
Leo
 
I also have spare M/Cs, and I always try a M/C first. When that fails, I go to the grease gun. The grease gun develops more pressure than a M/C or compressed air can. When that fails too, and it has happened, that's when I go to the pot of boiling water for 15 minutes followed by the grease gun.
I am a fan of heat guns, as has been mentioned, but not for this application. This is a case where you have a large chunk of metal that you want to get good and hot. You can set the water with the caliper to a simmer, and then go do something else for 15 minutes till it's ready for the grease gun.
 
The grease is messy for sure but agreed, the pressure developed is unmatched by anything else commonly available.
 
Hey guys thanks for the feed back, coming from a guy with no garage... I know sucks hard. My friends don't have a grease gun either, not sure justifying a grease gun for this will be worth it. I might try the compressed air method. Also visually trying to wrap my head around the flipped method. I'll post pictures when I have time, right now they're soaked in a bucket full of diesel fuel.
 
You can't lube your swing arm pivots without a grease gun.....

$23.00 at Canadian Tire

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The air compressor in my shop produces about 135lbs of line pressure. My hand operated grease gun is rated to 90,000lbs pressure. (I know that sounds nuts) Compared to the air compressor the grease gun is an irresistible force, even if messy.

If you do not own a grease gun you should. It's a very basic maintenance tool.

roy
 
I had some stuck pistons and the compressed air only made them come out a bit and didn't want to deal with messy grease. Since I knew I was going to replace the pistons, I a drilled a hole through the piston. I then tapped the hole for a 10mm bolt. As you thread the bolt, it bottoms out and makes the piston corksrew out. After is was out, I soaked the calipers in Metal Rescue to get all the rust out. No scrubbing required.
 
cobrasneverdie said:
I might try the compressed air method.
Click to expand...

Word of caution. Imagine what direction the piston is going to go when/If it lets go with 150-200psi pushing it. Will you be watching it move from the front? Is it going to hit your eye, the petrol can, ricochea.

Grease may be messier but without thinking air can be very dangerous.
 

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