The vehicle referred to here is mine. One of the reasons I think a loose timing belt might be my problem is that the overheating is intermitent. My first mech. replaced the radiator,water pump, thermostat, belt, belt idlers and the belt tensioner. He had to reorder the tensioner 4 times because the first 3 had almost no tension in them. The old belt had a lot of scuff marks on the back of it and he thought it might be slipping on the WP. I took the car to a Subaru dealer because of continued overheating. It did not overheat for them, but did on the way home. They finally diagnosed the blown HG.
If the HG caused the overheating why does the OH come and go? Also what caused the first OH ? The radiator was bad (half clogged, probably from the stop leak Subaru put in it) if that caused the first problem why did a new one not fix it? I don't know the answers to these questions and, so far, no one I have taken the car to knows either. I really want to prevent this from happening again whatever the cause.
PS: If the belt can bounce due to lack of tension/dampenin/cold fluid or whatever, could it not be skipping on the water pump, causing poor flow?