brake master cylinder seals & fluid going off really quick

[downimpact]

Does anyone have the part number for the jap spec brake master cylinder seals?

 

Thanks

 

edited to add I seem to have problems with my brake fluid going off every 6 months, with only one track day and very little usage. Is this likey to be a symptom of needing to change the seals?

Edited August 17, 2011 by downimpact (see edit history)

[downimpact]

anyone please?

[Chris Wilson]

Here you are:

[downimpact]

Thanks Chris,

 

added question above as well, I'm hoping changing the seals will solve this problem as well.

[Chris Wilson]

The only way that brake fluid will "go off" and cause issues is if it absorbs too much moisture (all normal brake fluids are hygroscopic and absorb moisture from the air through the reservoir vent, and through hoses and seals via osmosis). IF the clutch fluid absorbs a LOT of water, and IF, for some reason part of the compressible system with fluid in it is getting mad hot through radiation, conduction or convection, it MIGHT boil. Brake fluid will obviously get hot via heat from the pistons and general brake area generated heat radiation What issues are you having? What type of fluid are you using?

[downimpact]

I recently changed the fluid about 4 months ago using ATE super blue racing fluid. Which has higher boiling temps than previous Motul 5.1 RBF600 I was using before. I've done one track day and less than 300 miles on the road. Now the fluid seems to allow plenty of travel in the pedal with reduced braking capability.

 

The previous fluid change again only lasted circa 7 months and was causing serious stopping issues again little mileage a couple of track days. I've since moved from Jap brakes to UK when the last fluid change was made, not sure how this could make a difference.

 

My only thoughts are somehow air must be getting into the system, maybe a new reservoir cap would help as well. I'm not noticably losing fluid though, through the life of the pads other than as the pads wear down.

 

Reason for changing seals in master cylinder - after a session on track, once the brakes have re-cooled before going out again, the pedal will travel excessively without stopping power and then after a few pumps/corners it is back to normal. This happened when I was running both jap spec and now UK brakes, and through a number of different brake fluid changes.

 

I also get slight vibration under braking but suspect this is due to slightly wapred discs as they are second hand and badly lipped. I'm changing these for brand new as well.

 

Also to note I have do-luck braided lines and a cusco brake stopper.

 

Any advice as I'm losing patience with the braking system, I was hoping changing the master cylinder seals would resolve the last problem, but after driving yesterday and how bad the brakes were responding I wonder if something else could be causing issues.

[Chris Wilson]

If it's fluid boiling issues it would result in the pedal going right to the floor with zero retardation. I doubt it's fluid related at all. Off the top of my head I would suspect pad knock back from a knackered front or probably rear hub bearing, or a stuck caliper piston. If not strip the master cylinder, clean it in brake cleaner and blow out several times with an air line, making sure the TINY bleed return hole in the bore is clear. Rebuild with another seal kit if in any doubt at all, and see what happens. Good luck.

[downimpact]

Thanks Chris, will go with plan and see how it goes.