View Full Version : Radiator cooling

11-17-2009, 03:59 PM
98 tourmaster 400 cummins side rad has hydraulic fan. i think its running all the time and would like comments on this subject. having run cummins engines in highway and off road trucks i'm sure it is running to cool feeling cummins needs its heat. an thoughts. thanks Jack

11-17-2009, 08:05 PM
Doesn't the coolant thermostat control the engine temperature and not the running of the fan?

In other words, it is true that the fan will cool the coolant and lower the temperature IF the coolant thermosat opens when the engine temperature is up to the level that coolant can flow thru the engine and radiator. If the temperature is to low, then the coolant thermostat will close not permitting the coolant to flow or to restrict the flow to keep the temperature at a constant.

So it really doesn't matter if the side radiator fan is running all the time, the coolant thermostat controls the temperature of the engine.

The only reason that they have a fan clutch on a rear radiator diesel, is to save horsepower that is used when the fan is not needed, NOT because to keep the temperature of the engine up. It is also controlled by the coolant thermostat.

It is also the same on a front engine diesel or gas motorhome or vehicle of any type.


11-17-2009, 11:19 PM
Thanks Ron for the come back. I think the fan maybe run by a sending unit on the engine and that maybe the problem. By rights the fan should not come on until coolant temp reaches 180-220 in an engine this size, so when you spoke of the thermostat that maybe the problem but the fan should not come on until temps are reached. The coach came from the south USA and may not have a high temp thermostat so does not get to temperature. I was just curious as to why the fan ran all the time and if others had experienced the same situation. I will take all info and try to get temps up in the engine. Thanks again for your help Jack