Topic: brake caliper not moving

[stay youth]

Hello so I have been hard at work trying to get my disk brake working properly. The caliper moves in the body without the seal installed. When i install the seal it doesn't want to move freely. does the seal swell with the fluid?When i try to bleed the system the fluid is sucking through the lines and come out the bleeder as though its just completely bypassing the piston. I have never worked with a disk brake before so its all new to me. Any suggestions?


thanks so much!

[Sweep]

Hello so I have been hard at work trying to get my disk brake working properly. The caliper moves in the body without the seal installed. When i install the seal it doesn't want to move freely. does the seal swell with the fluid?When i try to bleed the system the fluid is sucking through the lines and come out the bleeder as though its just completely bypassing the piston. I have never worked with a disk brake before so its all new to me. Any suggestions?


thanks so much!

When you take out the old seal you'd have to scrape away the years of gunk before the caliper moves freely.  You might try removing the seal and scraping so the seal can seat properly.

[TwoTired]

does the seal swell with the fluid?

Not if it is a proper seal from Honda.

When i try to bleed the system the fluid is sucking through the lines and come out the bleeder as though its just completely bypassing the piston.

The bleeder open, relieves pressure.  You need pressure to move the piston.  You open the bleeder to release air from the system which is compressible.

Sweep is quite right about the seal groove in the caliper.

Did you read the brake FAQ?
http://forums.sohc4.net/index.php?topic=259.msg207521#msg207521

Cheers,

[stay youth]

thanks for the replies, I did read that FAQ on brakes a few times, but I was unsure if the seal was swelling causing it to be too tight a fit. The seal is a NOS honda part. Should the piston not drop out with gravity with the seal installed?

Thanks again!

[Kevin400F]

The piston will NOT simply fall out of the caliper with the seal installed.....in fact, it is a fairly tight fit.  Keep in mind the piston only moves a tiny fraction of an inch when the brakes are applied.   In fact, the "grip" of the square-edged seal on the piston is what helps retract it back away from the pad when the fluid pressure is released to minimize brake drag.

[TwoTired]

Should the piston not drop out with gravity with the seal installed?

Goodness no.  One reason why it is a square section ring is to actually pull the piston away from the caliper a few thousands when pressure is relieved.  It must be able to grab onto that piston and hold it in place to do that.

Cheers,

P.S. Kevin types faster than I do!

[stay youth]

Ok thank you guys so much, Sorry I know these seem like stupid questions to you but its still new to me. So i can push the piston into the body and the action of the pumping will move it? I should also use some silicone grease correct?


thanks!

[TwoTired]

Pure silicone, yes.  No petroleum blend.  But, this only goes on the parts that don't see brake fluid contact.  Do NOT want silicone in your brake fluid.
For the seal itself, I highly recommend Brake Parts Assembly fluid.  It IS compatible with brake fluid and helps keep moisture at bay to allay future corrosion.  Can be hard to find these days, though. 

Cheers,