overheating update: still stumped

[Mr. BILL]

For some reason, I can't post on my thread already started on the subjuct. So, I thought I'd start another.

Jeff, The t-stat is a whaller. I tested it in a pan of hot water and it works.

I decided Sunday night to start over. So I pulled all the hoses and flushed the daylights out of the block and back flushed the radiator. Some cloudy white water came out at first. I kept at it until the water coming out was clear.

I put it all back together and filled/bled it according to Bentley's proceedure. I started it up and it stayed at normal temp at idle for 5-6 minutes. I took it for a spin and didn't go 200 yds before the temp started going to 3/4. It was late, so I shut it off and went to bed.

This morning, I topped it off and tried again. Same thing, let it idle 6-7 minutes and took it for a drive. This time, I made it twice around the block before it started to get hot. Before I shut it down, I opened th bleeder screw and only a steady stream of coolant came out. I reved the engine for a bit and still no bubbles. So I'm fairly confident I have the air out. BTW, the heater is putting out copius anounts of warm air.

At this point, I think I've eliminated the t-stat and air. I have a new water pump, so I'm ruling that out as well. That should narrow it down to the radiator, fan clutch, aux fan and god forbid, they guy sold me the wrong hedad. Although the two heads are identical from the outside. It's supposed to be off n '89 325 and of course mines a '90 525, both M20's.

Clues that may help are: the hose on the lower passenger side of the radiator, never gets hot, or even warm.Same with the crossover tube. When I removed the hoses from the radiator, it took almost 10 minutes for the radiator to drain. Just a steady stream like someone taking a whiz. I don't know if it getting hot is a result of actually driving, or because after 8-9 minutes it gets hot, which it does.

I was all set to but a new radiator, but then someone suggested it could be the fan clutch, which I'll check in the morning. I'm about to give up and let my indy figure it out. However, I hate to admit defeat. So, I'm asking one last time (for this project) for any ideas.

Finally, a big thanks to all who have helped. Especially winfred and Regal. I can't thank you all enough.