Author Topic: Brake Seal Expanded - help please  (Read 1144 times)

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Offline kine8282

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Brake Seal Expanded - help please
« on: February 06, 2009, 06:00:59 pm »
I've been rebuilding my front brake caliper and bought a brand new seal for the brake piston. I was using brake cleaner on the caliper and when I was about to install the new seal and used silicone grease. I started to work the seal into the groove and found that the new seal started expanding! I'm assuming its some kind of chemical reaction to either the brake cleaner or the silicone grease.

Has this happend to anyone? does this mean I've gotta buy another seal? will the seal dry and go back to normal?? please help
1975 CB550K aka "Nefertiti"
1978 CB750K aka "Kate"

Offline R. Hykawy

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Re: Brake Seal Expanded - help please
« Reply #1 on: February 06, 2009, 06:30:46 pm »
 the seal has reacted with the silicone grease and has swelled. Unfortunately I don't think it will return to normal get a new seal and clean out the caliper of the silicone grease.
Richard Hykawy

Offline OldSchool_IsCool

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Re: Brake Seal Expanded - help please
« Reply #2 on: February 06, 2009, 06:39:41 pm »
1. Prolly the brake cleaner is the culprit for the swelling
2. your seal is shot
3. don't use silicone grease on you brake piston, it will run when heated, fouling your pads
4. read the brake FAQ for what to use.
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Offline TwoTired

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Re: Brake Seal Expanded - help please
« Reply #3 on: February 06, 2009, 06:43:22 pm »
Unless you are using silicone brake fluid, you do NOT want ANY silicone mixed with it.
No brake fluid wants ANY petroleum grease mixed with it.

If your seal has expanded, it has absorbed what ever you treated it with, and should be discarded.

There is pure silicone grease, and there is grease with silicone in it.  They are not the same thing.  Reading labels can alert you to the difference.

Brake seals are installed with brake parts assembly lube  (preferred, but hard to get these days in some areas), or whatever brake fluid you are going to use in the hydraulic system.

If you rinse your swelled seal in brake parts cleaner solvent, and then let it air dry for a few hot days, it might shrink back to proper size.  (But, I wouldn't use it, unless a dire emergency occurred.)

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Offline kine8282

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Re: Brake Seal Expanded - help please
« Reply #4 on: February 06, 2009, 08:32:33 pm »
thanks for chiming in guys. one more thing: before the seal expanded, i actually installled it into the caliper groove without any problems then applied (mistakenly) the "silicone" grease to lube the piston in place. I put the entire assembly together and then bled the brakes. the reason why i dismantled the front brake again was because the caliper was dragging...do you guys think its because the seal was already expanding while it was in the groove thus binding the caliper?

I ask because I do not want to rebuild the MC if the expanded seal is the reason my brake piston doesnt retract. your thoughts? 
1975 CB550K aka "Nefertiti"
1978 CB750K aka "Kate"

Offline Spanner 1

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Re: Brake Seal Expanded - help please
« Reply #5 on: February 06, 2009, 08:51:13 pm »
Please check-out my post about front brake pads not retracting,,,I can't believe it's all the way back on page 33 !! Is the brake lever 'stiff' and the bike hard to push forward and back ?, if so please go to p.33 for cure.
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Offline kine8282

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Re: Brake Seal Expanded - help please
« Reply #6 on: February 06, 2009, 09:12:43 pm »
the brake lever was super stiff like it was engaged all the time and so the front wheel wouldnt turn. I read your post, did you have to completly tear down the MC to clean the holes or can you just clean them out without doing a complete tear down
1975 CB550K aka "Nefertiti"
1978 CB750K aka "Kate"