Engine Overheat at Idle, and a few other questions

[ylwjacket]

2005 3.0 X5, 130k miles.

This is similar to my other thread, for which I apologize, but I am wondering if my problem is not the aux fan.

My engine overheats, and a Coolant Temp Warning comes up on the dash at idle. It happens when idling at uphill locations. Doesn't seem to happen (or at least I haven't noticed it) at downhill locations. When moving, the temp returns to normal, and everything is fine. I did have the a/c on when it happened.

I had been thinking it's the aux fan, but I'm not so sure now. It was a little low on coolant, as apparently I didn't bleed it enough. I added more, until the expansion tank was full while cold. I haven't driven the car since then.

I replaced the thermostat, water pump, and upper and lower hoses. Dealer told me the thermostat was stuck open, after replacing the expansion tank after it grenading while driving. When the tank blew, all the coolant leaked out, I pulled over, and got towed to the dealer. They replaced the tank, and told me the thermostat was stuck open. While replacing the thermostat, I went ahead and replaced the water pump and upper and lower hoses.

Also, I am ordering parts for a oil filter housing gasket and valve cover gasket. When I replaced the water pump, the belts looked fine, but I am wondering if I should go ahead and replace them while I'm doing the oil filter gasket. Not sure how long those last. For $35, I figured it might be worth it to do while it's apart anyways. What's the cycle on belt replacement?

Thanks for your help.