Clutch pedal goes soft under wot?
 

I am trying to track down a problem that appeared the other day, basically when I go under wide open throttle into boost the clutch pedal starts to become soft after 1-2-3 it sinks all the way to the floor. Im running a 6 puck clutch with strong pressure plate. Changed the slave cylinder and bleed the system problem solved.

Now tonight the same thing happened after 2 days trouble free, it feels like there is air in the system but I cant see how. Maybe slave cylinder gone bad?

I was thinking about the brake booster, will check the one way valve make sure when under boost its not letting any air through it.

Anyone had this problem or have any suspision of where this could be comign from?

I will try bleed it again.

How old is your clutch master cylinder? Usually people change both the master and slave cylinders when they're having hydraulic clutch problems, since the system can be tempermental if either one is out of whack. Other than that, are there any possible leaks in the clutch hydraulics? What tranny fluid are you using, and how's its fluid level?

Re: (inspyral)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by inspyral &raquo;</TD></TR><TR><TD CLASS="quote">How old is your clutch master cylinder? Usually people change both the master and slave cylinders when they're having hydraulic clutch problems, since the system can be tempermental if either one is out of whack. Other than that, are there any possible leaks in the clutch hydraulics? What tranny fluid are you using, and how's its fluid level?</TD></TR></TABLE>

They are as old as the car, have around 100k on them, I replaced the slave cylinder bleed the system then it was fine after some hard driving. Same problem occurs, the pedal goes soft, once I bleed it again its fine again, my brakes dont seem to be affected tho.

I have a feeling the heat from the turbo is heating the clutch line and boiling the fluid, making it bubble. This is a vw engine where turbo its at the other side ie on the firewall.

I will double check for leaks but I doubt I have any, i will reflush the whole system, replace it with some higher heat rated fluid and wrap all my clutch lines and master cylinder from turbo heat.

This happens only under numerous wot passes, meaning loads of heat from turbo causing huge increase in temp right next to the clutch lines although they are covered with a aluminium sheet I have a feeling its not enough.

I'm not sure about VW's, but on Hondas, the clutch MC usually leaks near the piston rod that connects to the pedal. As for your fluid boiling, you might want to step up to something like Motul or ATE fluid that has a higher dry boiling point and see if that helps.