We have a 2001 Forester with 90K miles on it. It has gotten hot (not overheated) twice. Both times it blew out water in the overflow. The first time, I filled it with coolant mix and a new radiator cap and it was fine for 20K miles. The second time the upper rad hose was collapsed shut, the cap was holding a vacuum. Anyone else have cap problems?---Jack

The collapsed hose is a sign that the coolant is going somewhere.

 

I hate to say it, but you might take the cap off when its cold and look for bubbles in the coolant, sure sign of a blown head gasket.

 

 

A new Subaru OEM cap is cheap insurance though, throw a new one on and see if that makes a difference.

It has not used any coolant before or after and not overheated going over US 80 from Sac to Reno after I replaced the cap. The original cap had about 60K on it. Do aftermarket caps not work well on Subarus?

aftermarket parts are really hit or miss on these cars, thermostats in particular are generally best to go Subaru only on. I can't imagine you'd save much by going aftermarket on a cap though.