Recently my '83 240D has been running far hotter than I like - the needle hovers just below 100 during normal driving and will push slightly past 100 during heavy highway driving (cruising at 75-80 mph).

After driving, the upper radiator hose is very hot to the touch and pressurized, and the lower radiator hose is cool or slightly warm and also pressurized.

I'm guessing it's the thermostat; anyone want to verify this before I get all dirty to replace a part that's not broken?

I have a spare radiator that I pulled off a junker over the weekend (hit the jackpot at the local U-Pull-It), but I don't know that it's in any better condition than the one in my car. It's not an OE part, and it doesn't have the reinforcing band inside the tubes where the hoses attach. I suppose I'll take it to a local radiator shop to have it checked out. I don't want to waste my time with this if it's a thermostat problem though.

Thanks.

- Nathan
'83 240D, 250k miles