Couple questions as the heat here in Texas starts to climb.

The mechanical clutch based fan in the 240's (1991 240 wagon in my case)

1. how do you tell if the clutch is bad?
2. how much of a difference "Tropical" clutches make, both on cooling and on MPG?

 

1) with the engine warmed up stick a rolled up magazine in the fan. If the fan slows/stops it's bad. If it tears the magazine apart it's good. ( not based upon actual experience but from what I've seen on YouTube )

2) I have no idea

 

Well I checked that, I guess the issue is not that it fails to spin, but it seems almost seized.

it’s much tighter than other 240's I have had, but it might just be the Tropical clutch...idk

Do you know if this clutch is thermally dynamic, in that it tightens up as it gets warm, listens up as it cools? It is AISIN brand, but idk if its original or not (27 years old at this point if it is OE)

 

It depends on how hot it is. A couple things...
Start up your car from cold and let it idle for no more than 5 minutes. You don't want your thermostat to open. Turn off your car, and spin the fan- it should spin quite freely.


If it doesn't, then your fan will be running full speed all the time, which is not bad for cooling mind you, but not great for fuel economy. A properly operating clutch will "loosen" on typical highway driving. In colder climates, with an always-on clutch, your car will take longer to heat up, especially problematic up north. Considering your climate, you may not need to worry about anything.


If you feel like addressing the issue, you can easily DIY the fix, as long as the external thermal spring hasn't rusted through and/or the internal valve still operates. You basically take apart the clutch with an impact wrench, drain the fluid, replace said fluid with new fluid (I used RC-car differential fluid) and put it all back together.

 

they have a bimetal strip that works a valve, and are filled with a hydraulic fluid... idea is when the engine is cold, the fan doesn't spin very fast, when the engine gets hot, the clutch engages and the fan spins faster, but its still kept from spinning TOO fast as its not needed so much when you're moving at speed.

I'm not sure ATF is the right thing to put in these. They are filled with a pure silicone oil, and you can get this from Toyota (note that Aisin is a primary Toyota supplier, the AW transmissions in 240/740/940 are Aisin-Warner). See Here are the instructions: for the refilling procedures. The Mercedes folks who have similar viscous fan clutches like to use the thicker 10000 CST oil.

 

I "tested" the fans in my 4 Volvo's. They all "passed" the magazine test. They all fail to spin freely with the engine off.

This 8th post in this thread from turbobricks has some good info I believe...

http://forums.turbobricks.com/showthread.php?t=264636

 

heh. Mercedes guys use a large carrot (the mess hoses off nicely), or a rolled up newspaper to test the fan when the engine is hot. never heard of a mercedes fan locking up, just not engaging. The Mercedes OEM for the fan clutches is Behr, and most of the MBZ guys I know think anything else is unreliable junk.

 

Thanks for the help everyone! As it turns out this is one of the "Tropical" clutches, so it is a bit different than the other Volvos I've seen. If passes all the tests however so I am happy with that.