Clutch fade / fluid boiling at Altitude

[virginiajim]

Bet it doesn't taste very good either.  Seriously, I don't like the look of that.

Lets us know if the seal fixes it. I guess you'll have to go to high altitude to prove its fixed

Assuming he ever gets it bled....the clutch hydraulic system can be a bear to bleed and get right.

[viper]

can someone explain how a leaking seal causes brake fluid to boil at altitude, only one thing makes it boil and that's heat, obviously a little less heat at altitude?

[Charlie747]

can someone explain how a leaking seal causes brake fluid to boil at altitude, only one thing makes it boil and that's heat, obviously a little less heat at altitude?

We've had this problem before and if I remember correctly it was cured by a thorough bleed of the clutch fluid ie bleeding till new fluid is throughout the system................It is very important to use a new freshly sealed supply of fluid due to the hydroscopic nature of the product.  Once contaminated Boyles Law shows its ugly head as you loose atmospheric pressure at altitude and the water contaminated fluids boiling point is reduced thus allowing vapour lock to occur   

[ozzmotor]

Hello there.
  I have had exacly the same issue with my 2007 GTR . Clutch would get worse the higher I when. At top if I pumped the clutch full operation returned sujesting air expanding. Has this issues cause been identifed as I am going the Switzerland in May and would like to rectify.
Cheers ozzmotor

[viper]

ive been over all the high passes on my GTR in the Alps  and never had an issue with either clutch or brake fluid driven systems. However I do replace my hydraulic fluids every 2 years so its in tip top condition. If your fluids are a bit old then id have these changed along with your coolant before the trip and im sure you wont have a problem.

[ozzmotor]

hello all.
As I has said on previous posts I had this issue also on my 2007 GTR.  no problem in the UK but a nightmare in the ALPS .I wanted to cure this before this years trip.I fitted a reconditioned slave cylinder,the old one was actually fine. These units are twats to get off so i ended up tapping the 3 holes out to M8 thread and jacking it out against washers after breaking out the plastic spacer out.!!!!! Be warned and be careful.It would be easy to cause expensive damage removing slave.
  The clutch felt exactly the same. bearing in mind the I was only at 500 feet above sea level in the UK
Next I fitted a reconditioned master cylinder with genuine parts(£39}. This made a massive difference to the clutch feel, even in the UK..a different animal.In all cases I bled the system from the bottom up with a giant syringe.
   I have just returned from the Pyrenees and the clutch was fine up to about 2000m.
  In my opinion, in my case the issue was the master cylinder and seals. Slave was fine and in good condition and the system was always air free. Also I still have the OEM rubber  hoses fitted to the bike. It was like the master was not refreshing the fluid charge on release of lever and got vaguer the higher I went. No fluid boiling, no engine heat.
As I didn't have the liberty of doing one thing at a time and driving up a mountain to prove if the issue' I can't say for sure, but I work as a  mechanical  engineer with hydraulic systems and that's where my money goes.

[Charlie747]

Glad you're sorted