Viscous Fan on from cold start
I have a 230GE (460), the viscous fan turns quite freely when the engine is cold but still operates all the time, even when the engine is cold. I thought the fan was supposed to engage when the hub heated up?
Could someone explain how it should work?
Hi Andy the coupling has limited drag when cold but will turn by hand with very little resistance.the common failure is when the blades continue to "idle" at temperature as this can cause the engine to overheat. if your temp' guage is pointing around the twelve o'clock position after 10 miles normal driving with an ambient temp' of + 10 degrees all is working as it should. rev the engine within one minute of starting and the fan will turn but with minimal airflow.....
Hi Andy until the thermostat opens there is no circulation of the water through the engine from the radiator...only after the stat opens fully (at about 65 degrees C) allowing hot water from the engine to pass through the radiator does the coupling tighten up and the fan go into cooling mode.....even with a hot engine you can still move the fan blades a bit...but you will notice much more resistance. fuel economy can be affected when the fan is permanently engaged.
OK, that's the problem the fan is working from cold start with the thermostat closed, so the thermostat opens when the engine heats up but the fan is working (quite a bit) so the water in the rad cools more than it should, hence the temp never rises much above the white line.
Is that possible that the fan fails in a way that makes it work when it's cold, instead of the usual failure when it's hot. I mentioned the fact that I can turn it easily by hand with the engine off / cold because I guess that means it's not locked by the tabs. I assumed if the tabs were locking it I couldn't turn it when the engine is off.
Hi andy,
I would check your thermostat first if your engine is not reaching its right temperture, even if your fan was locked solid it wouldn't be able to keep it that cool as its only effective at cooling water in the radiator and if water is running through the rad at low temps then the thermostat needs replacing. which a far chearper option.
I thing the thermostatic coupling on the fan just uses a fluid inside that when heats up gets thicker to create more resistance to make the fan turn more rather than tabs engaging.
I think you're right, I will order a replacement thermostat just in case.
Still wondering whether the fan should even be operating at very low temperatures, it's certainly not so loose that it would stop easily by hand when ticking over cold.
Hi Andy the ambient temperature is not low enough yet to allow the fan blade rotation to reach minima at startup..you will notice that your automatic cold start enrichment is almost non existent at + 12c ambient as it works on the temperature of the water circulating around the engine.if your water temp indicator does not point to around twelve o'clock after ten/fifteen minutes driving in the current climate then look to the thermostat as being the problem...to test the indicator remove the wire from the sender and touch the metal end against the side of the engine..you should get full deflection of the pointer on the guage ......
The temperature gauge is working, I have had some overheating because I forgot to top the rad up so I've seen the gauge at full range. I will look for normal temp. next time I'm driving any distance. I was just about to call the dealer for a new thermostat but maybe I can lay off that to begin with.
Thanks for answering my question, the temperature is not low enough for the fan to not operate.
JOIN THE GWOA
This website and forum are provided for the benefit of enthusiasts and owners of all Mercedes Benz off road vehicles, in particular the G Wagen. The costs of development, upkeep and provision of the site are met entirely by the annual subscriptions of club members. If you are using the site and are not a member of the G Wagen Owners Association please consider joining. You will have access to areas on the site that are not open to non members, to club trips and meetings and to technical assistance. In addition your contribution (only £25 annually) will help us maintain and develop our website for future users.
Who's new
- Jaffa_JIM_23
- Wrabstar
- GG
- KTMSCANIA22
- 280ge
Thanks for that, the fan is quite easy to turn with the engine stopped and cold, I can feel some fluid resistance. There is lots of airflow and the temp gauge is staying low after a few minutes idling still only just out of the white section.
I would not describe the airflow from my fan as minimal when reving after a few minutes idling.