Front brake issue: Possible airleak?

[mattd1205]

Ive been trying for days to get my front brakes on my gs850 working properly. I can buildup pressure if I pump the brakes enough times but if i let them sit for a few seconds they will go back to being spongey. The calipers have been rebuilt and there doesnt seem to be any fluid leaking from the calipers I have bled the brakes numerous times and there are no fluid leaks along the lines and joints. I am at wits end here!! Any ideas on what could be going on?

[GSXR7ED]

I have the opposite...I can't get any pressure. I'll have to remove the caliper and double-check the seal that wraps around the piston. I had a bear of a time getting it to fit properly and now I see why it needs to seat correctly.

Good luck figuring it out...maybe you need to EVAL and check all the seals.


Ed

[GSX1000E]

Most likely, one of the seals in the master cylinder has a rupture/tear and the fluid is by-passing internally. Or installed backwards. Has anyone been inside it? Not too difficult to repair.

[jwhelan65]

Can you post a pic of your caliper?

[Nessism]

Did you use OEM caliper seals or K&L? I've seen this with aftermarket seals because they were too tight and wouldn't let the piston adjust to the proper position away from the disc.

[GSXR7ED]

***Informational Only***

While we're waiting for OP to post up pics and since this is relevant, here's my install of OEM parts for my caliper. I think when you look at the last pic you'll notice I don't have a proper seal.













I'll remove the caliper and get a better seal today.


Ed

[jsandidge]

tutorial

There's a tutorial on BassCliff's site showing how to properly install that dust seal. You should be putting it into the caliper groove first, then finagle the piston in. The dust seal will snap into the groove in the piston once you push it down all the way. Check out the tutorial, it has good pics.

[Nessism]

Install the dust boot over the piston and slide it down as far as you can. Then put the boot into the caliper groove before you install the piston into the caliper bore. Brake fluid lube will help the parts slide together. Once the piston is in the bore there is almost no way to get the boot into the caliper groove, it must be installed prior.

[GSXR7ED]

Thanks guys...and OP...look at the tutorial...we both need to learn something here.


Ed