viscous fan good?

[tater]

i'm going to be checking out my son's overheating problems on his '91

How do you check for proper operation of the fan?

thanks tfrane

 

[1stgen4evr]

fan

I see you have some lookers but no takers on the question. I will hazzard a guess and someone else can shoot me down or agree, whatever. If the fan turns when the engine is running while stopped with the hood up, it probably isn't the fan. Stop the engine and feel the 'connection' of the fan. You should feel some drag.



Now they do fail so you can not rule out the fan clutch completely. You need to know how long the engine runs before overheating. Is the coolant clean looking. I don't mean clear water but rather not rusty crapy with any contamination. (Always be careful about removing the cap on the radiator. ) Is the radiator crossflow or vertical flow. The later ones cool better. More times than not, if I have a cooling problem, it is the radiator getting clogged. Draw the coolant down so you can see the tops of the flues and see if they are getting plugged with 'plaque'.



There is a product at NAPA made by CRC called Enginkool that actually does some good with cooling.



OK, someone else jump in here.



James

 

[cerberusiam]

The first thing I would do, if you haven't already, is put a manual gauge on it and make sure it is actually getting too warm. The early trucks had weird problems with the gauges and electrical that reported warm temps when they actually weren't, but, some were and switching to the cross flow radiator was needed.



If it is actually warm then James is dead on correct on where to start. The updated fans and clutches seem to move a lot more air so you may want to look into them also.

 

[BHiggins]

I replaced several fan clutches on my 1990 but the problem (as 1stgen4ever already stated) was a clogged radiator. Upon inspection, it looked good, clean anti-freeze and no apparent fouling. The way I figured it out was to get the truck warmed up and then shut it off. I felt the radiator with my hand and found a large cold spot in the middle right where the spring for the fan clutch is... several rows were clogged and not allowing hot air to get to the spring and actuate the fan. A new radiator fixed it once and for all. The whole time I thought it was a non-functioning fan clutch (as I said, I went through several (three) fan clutches before I figured it out), but the fan not functioning was CAUSED by the bad radiator. This may not be what you are experiencing, but it's a good place to start and easy to check.

 

[tfrane]

Thanks

Sounds like good info. I'll start my trouble shooting as you guys described.

tater

 

[RWWinslow]

I just went through this on my non-intercooled 1991. The newer fan clutches are a lot stiffer than a worn out fan clutch - on the early 91's this is a dealer part so go to the dealer and check to see if the new part is stiffer to turn than the clutch installed in the truck. If so, then the fan clutch may need replaced.



I also changed my radiator at 380,000 miles - it was 'plaqueing up'. Since I had the early 1991 (non-intercooled) mine is a vertical flow model. When I changed the radiator I cleaned out the A/C condenser of bugs and mud and debris - it was probably 15 to 20% plugged - this also had a positive impact. OEM new radiators for these rigs can still be purchased through Dodge or radiator dealers.



I also installed a new fan clutch and it made a significant difference - especially at idle!



Hope this helps . . . . . .

 

[EZeis]

If your 91 truck is a early model, maybe this TSB on the t-stat may help.



http://dodgeram.info/tsb/1991/07-01-91.htm





Earl