Viscous fan

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mikeateves

New Member
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124
Hi,
I think my P38A diesel is running a bit cool (temp gauge never gets much off the blue zone). Before going down the route of replacing the stat I wondered if it is the viscous fan. How easily should the fan turn when the engine is cold? I expected it to rotate pretty freely but even giving it a firm push on the fins it only turns a few degrees before stopping. Is this normal?
If the fan is faulty is it worth swapping it for an electric one? If so any recommendation as to make?
Thanks,
mikeateves
 
mikeateves said:
Hi,
I think my P38A diesel is running a bit cool (temp gauge never gets much off the blue zone). Before going down the route of replacing the stat I wondered if it is the viscous fan. How easily should the fan turn when the engine is cold? I expected it to rotate pretty freely but even giving it a firm push on the fins it only turns a few degrees before stopping. Is this normal?
If the fan is faulty is it worth swapping it for an electric one? If so any recommendation as to make?
Thanks,
mikeateves
Click to expand...

Mine's the same : watching out for the advice you get !
 
When cold the fan will still be sticky due to cold thick Fluid...on turning for the first few seconds the fan will spin quickly until the fluid warms slightly and thins out....

As the engine warms, the fluid then thickens until such time as the engine has gone to a certain point when the fan will start turning faster to aid cooling....

Wammers has detailed the Viscous fan operation and testing (Usually using a rolled up newspaper).....
 
If unsure remove fan , its ok too and see if there is a
Dramatic change if so there is your answer if not looks like a removed or stuck stat.
 
I now run with the Datatek mod, no fan and removed the fan cover so easy access to stat, wtaer pump and belts.

I would suggest dointh just the same and use a new LR stat if you change it.
 
Just a warning to all you youngsters out there.
When testing your fan please use an old-fashioned newspaper.
Using a Kindle or iPad is not recommended.
If you wish to attempt this please supply photographs.
 
mikeateves said:
Hi,
I think my P38A diesel is running a bit cool (temp gauge never gets much off the blue zone). Before going down the route of replacing the stat I wondered if it is the viscous fan. How easily should the fan turn when the engine is cold? I expected it to rotate pretty freely but even giving it a firm push on the fins it only turns a few degrees before stopping. Is this normal?
If the fan is faulty is it worth swapping it for an electric one? If so any recommendation as to make?
Thanks,
mikeateves
Click to expand...
The Fan is normal when cold, you need to test it when hot.
The most likely reason for it running cool is a duff stat, even if the viscous is locked solid the stat should still maintain near normal temperature. The only other reason would be a duff gauge sender giving an incorrect reading.:)

Don't waste your cash on an aftermarket electric fan, the aircon fans do the job just fine with my mod.
 
Datatek said:
The Fan is normal when cold, you need to test it when hot.
The most likely reason for it running cool is a duff stat, even if the viscous is locked solid the stat should still maintain near normal temperature. The only other reason would be a duff gauge sender giving an incorrect reading.:)

Don't waste your cash on an aftermarket electric fan, the aircon fans do the job just fine with my mod.
Click to expand...

One small snag, mine doesn't have air con. I'll try taking the viscous fan off and see if that makes a difference, shouldn't need it anyway with this weather.:rolleyes:
 
mikeateves said:
One small snag, mine doesn't have air con. I'll try taking the viscous fan off and see if that makes a difference, shouldn't need it anyway with this weather.:rolleyes:
Click to expand...

Just follow the instructions of how to test fan by hand in my "How to" at top of page. Wax stats very rarely stick open unless the spring has failed
 
Last edited:
Datatek said:
Exactly so. He proposes to remove the fan to cure it. That will be fine unless he gets stuck in traffic. To get it up to temperature he needs a stat that's not stuck open.
Click to expand...

I think he it taking it off to see if the temputre rises if so he knows its not the fan , if stuck open in this weather hardly going to get hot with stat stuck open might warm up a bit more in traffic then he will know temp senders working and that a stat is in order
 
defender300td1 said:
I think he it taking it off to see if the temputre rises if so he knows its not the fan , if stuck open in this weather hardly going to get hot with stat stuck open might warm up a bit more in traffic then he will know temp senders working and that a stat is in order
Click to expand...
I will guarantee that it will overheat in a slow traffic queue of any length and risks cooking the head.
 
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