Op is there a reason you didn't go with the fail safe, I'm thinking of moving to the 180.

 

Too many times fail safe thermos put themselves into fail safe mode where they are open all the time....so...I just replace the thermo while I replace my coolant every where


Savanna:

Just because its Severe, its not going to roar all the time...it will roar (cool) at faster speeds compared to your standard use one. I am going to use a Hayden unit i think i put the part number here somewhere in this thread

 

Hayden (owns Imperial) tech department confirmed by email that it is a smooth transition when the unit warms up. So all things being equal, both the $49 Chevy 4.3 liter model (no air) and this $58 S10 4.3 liter model have the same drain at normal operating temperature, as temp rises the severe duty one will move more air. So hopefuully MPG will not be impacted on the highway. However, tech support said it is not a factory advised unit - they actually claim not to make units exactly for our trucks. That unit is listed for Chevy and GM from 4.3 to 8 liter (honkin'). They say "The style, weight, pitch, length, etc of the fan blade determines which clutch to use. Hayden does not supply a fan clutch for your vehicle"

 

Exactly..since it moves at close to shaft speed instead of 60-70%