fan troubles pt 2

[Delorean17@xxxx]

Hi,
This fan problem is really driving me crazy. I have found that if I keep 
a steady speed at around 55 the fans will come on and not shut off for a few 
minutes. If I decrease my speed down to about 40-45 the fans will shut right 
off and everything is fine. I cannot figure it out. that makes absolutely 
NO sense to me or anyone else. heres a recap on whats been done, new 
otterstat, new hoses under manifold,new fan & fan fail fix, Grady thermostat, 
System pressure tested great, and the auto bleeder from DMC Joe.
The water pump is not leaking at all and the pulley has no movement at 
all. I checked it out good when I replaced the hoses under the manifold. 
The only other thing I can think of is something is restricting flow through 
the radiator.(even though It only has 18k miles) I will probably remove myne 
and have it cleaned sometime next week. Before I go ahead and do this can 
anyone think of any other possibilities.

Thanks
david