I have a 2000 Subaru Outback Wagon with about 80,000 miles and live in the San Francisco area. This car has a manual transmission and when I drive to the mountains over about 8500 ft, the clutch stops working (that is, the shift point goes to the floor). If I park the car for a day, the problem goes away.
My suspicion is that there is a pressure equalization problem here of some sort. The dealer has been useless (and they are at lower altitudes so I cannot demo this problem). Any ideas on what the problem is and what I can do about it?
Either the fluid in the clutch hydraulics has seriously disentegrated or you have a failing clutch master and/or slave cylinder.
You could try bleeding the fluid which is easy and cheap to do. You do not even have to go to the dealer for this; it’s very simple.
It could be that over 9 years the clutch fluid (which tends to absorb moisture) has become diluted and weak with age. This lowers the fluid boiling point and altitude can also lower the boiling point (roughly 2 degrees F for every 1k feet of elevation). You can see where this could be a problem.
It’s also possible that aged fluid could be doing in the clutch master/slave cylinders. If this is the case then both should be replaced because failure of one often is followed by failure of the other. Hope that helps.