Towing

[TonyN]

The elec fan comes on when you turn the A/C on, and also is comes on if engine temps rise about a set temp (about 100-105deg, but only on 2.4's, on 3.0's its A/C only.)

Its just an extra back up fan to help out the main fan.

[steved]

What was the cfm rating of the fan and did it have a shroud around it?

16" Profan 2260 cfm, a puller type with shroud.

[BUSHWHACKER]

And it was definitely pulling?
They are reversible by swapping the wires over.
I use the same fan as a pusher or puller to keep the 4.0 V8s cool no problem.

[steved]

It was defiantly pulling don,t forget the thermal dynamics of a diesel are different from petrol so while what is fitted to your V8 might be sufficient it did not work on my 3.0.

[TonyN]

Tis true, diesels just get hotter and hotter the higher the RPM's get. Vastly more than petrol motors.

Just air flow through the rad isn't sufficent, you need a properly working fan as well. Have fixed lots of trucks that start to get hot at 80mph under load just by fixing the viscous fan.

I'd try and sort the stock setup first, the viscous coupling is infinatly variable in load compared to coolant temps so is the most efficient setup if working properly and should keep engine temp more stable than a simple on and off elec fan.

Elec fans work, the stock fan works, for the average truck it dosn't make a lot of difference, is only when you start to push the limits you need to fiddle with it.

I'm sure elec fans are far cheaper to manufacturer, most petrol cars have elec fans, most deisel motors have viscous driven fans, I'm sure manufacturers know far more about it and have done far more reseach than any of us.

[Hawaii]

I had exactly the same problem on my 3rd gen - head, rad etc. were all fine (in fact head repaced the year before).

I fitted an additional transmission oil cooler (13 row) as a kit from e-bay. totally sorted it. Afterwards she towed the twin axle caravan up hill & down dale with no overheating

As tony said it's the gearbox fluid going through the bottom of the rad (assume yours is an auto) that overheats the rad coolant

Kit was less than £40.00, included the cooler, piping, clips & mounting straps