On Oct 6, 2011, at 9:19 AM, Ed McLean wrote:

> However, when following any vehicle, and more so if
> that vehicle was a large truck, the return coolant temperature would climb
> although the feed temperature initially remained the same.  As the return
> temperature climbed above 195� the feed temperature began also to rise,
> indicating the radiator was no longer able to control the cooling demands of
> the engine.  If I then moved out from behind the truck, the return
> temperature would drop, followed quickly by the feed temperature dropping.
> I was surprised that this effect was present even up to ~200' behind a truck.

I noticed the same thing this last spring, coming up 191/6 toward Price, UT fro Moab. Also, there
was a fairly strong following-wind/tail wind, blowing S to N. The combination of those 2 things
contributed to the coolant running at 10 degrees hotter. Whenever I would move out from
behind the vehicle in front of me, within about a minute the coolant temp would drop 5-10 degrees.

By the time I got to I-15 the wind was from the N and I could easily change lanes to avoid being 
behind larger vehicles and the temp was again, 10 degrees cooler.
My radiator was replaced 4 years ago and is in very good condition.

Bob