Viscous Fan Drive
 

Does anyone have recommendations for a Viscous Fan Drive?

I think mine finally took a dump. Yesterday it was fairly hot out and when I let the Heep idle for some time the electric radiator fan kicked on and I noticed the coolant temp gauge was above 210*F. I never did hear the blade fan roar. Temp indication stayed high while driving in stop & Go traffic.

This morning I inserted a digital thermometer between the fan shroud and the radiator support frame to measure the air temp exiting the radiator, blocked the grill side of the radiator with a sheet of cardboard, and let the engine idle up to temp. The themometer got to about 177*F and the blade fan never did kick in and the temp gauge read 217*F on my scanner. The electric radiator fan didn't kick in because it held 217* for a long time.

The viscous fan drive is supposed to drive the blade fan starting around 165*F. It was only 71*F OAT this morning so I think I will repeat the test this afternoon when it gets up to around 89* OAT.

I have used the GBD and Four seasons brand with good results. Both are available from rock auto.

Thanks, I'll check it out.

Hey Ken, in the name of science....while it's hot see how long it freewheels when the engine stops. (from idle). It might be nice to know what a bad one does.

Just took it on a 20 mile drive to heat soak the engine. The coolant temp stayed around 208*-210* indicated during the drive.

When I got home I left it idle in the driveway and inserted my digital thermometer in the fan shroud like this morning. It indicated 175*F. Then temp gauge started to creep up to over 210*, then the electric fan cut in (218*F). It cut out after the coolnt temp dropped to below 210*.

The blade fan didn't seem to be engaged the whole time.

After shutting the engine down I spun the blade fan. It free-wheeled maybe three blades. The same as this morning when engine was cold.

My conclusion is that the blade fan can free-wheel less than the five blades (Max) but the thermostatic bimetallic spring coil on the face of the fan drive could be defective - not engaging the silicone coupling at between 165*F and 180*F, as designed.

Now for one of my Unfavorite jobs on the HEEP - knuckle scraping R&R of the blade fan to change the bloody viscous fan drive.

Knuckle Buster
 

I got tired of knuckle scraping when removing the fan clutch. Now I wrap with tape a strong dowel rod to the wrench and can safely loosen and tighten while keeping hands beyond the blades and shroud.
Still have to get my hands in there some, but the extension sure helps and is quicker because it allows more movement in each turn.

IIRC, we got a Hayden fan clutch at O'Reily Auto Parts 4 years ago.....no issues so far and if there r, lifetime warranty.

Sounds like it's not spinning up at all.

Actually the idea had been, how long does it continue to spin right after the engine stops. I guess if it's not spinning, that test doesn't mean much! I'd seen posted that was a way to get an idea of how viscous/engaged, the fan is.

I think my PO put in some heavy duty thing. Been in there since I got the Jeep in 02. It's always the same, firm. It stops immediately, can "flick" it, to turn one blade only, (barely.

When replacing mine , I ended up getting the HD version (Omix-Ada > USMotorWorks sourced, as turned out)delivered, which I didn't know. Was quite a bit beefier, but it reduced the clearance towards the HB to less than what I was comfortable with...so took it out and now have a 4 Seasons in there. Works fine and brought temp back from above to under midline on the scale.

For what it's worth: my old VFC passed all the " is my viscous fan clutch still good?" tests that we talked about in the past....but turned out to be under par after all, when I finally replaced it.

I think if someone wanted to use the free-wheel test to determine how many blades turn (when the engine is cold) the best thing to do is start the engine, let it run for 15 seconds to one minute to reditribute the silicone fluid to its normal disengaged position* then do the spin test.

* ref. FSM Section 7-8.

Similar problems on my jeep. I hear the electric fan kick in but the engine-run fan I can only recall one time it kicked it. I had a new fan clutch on hand but the one in the jeep "felt" fine. Off to knuckle busting!

Yep.

Fixed
 

Well, it's fixed now. Went with a Hayden clutch from O'Reilly's.

When I pulled the new clutch from the box I turned the shaft to get a reference.

Installed the blade fan/clutch assembly. Turned the fan blades and the resistance was about the same as prior to install. Ran the engine for 60 seconds and turned the fan, it turned more freely now.

Started engine and let idle. The clutch was hunting, engaged/not engaged.

Took it for an 8.4 mile drive to heat soak the engine. While driving the indicated temp was around 208*. Got home and left it idle. Inserted my meat thermometer and the radiator output air temp was 164*F. The fan clutch was fully engaged.

Let it idle for around 10 minutes. Scanner temp held at 213*F. Indicated looked like 210*. OAT was 71*F.

Pic of my meat thermometer installed. The FSM has you drilling a hole in the shroud to install the thermometer. LOL.

Attachment 320777

Also went ahead and changed mine with a hayden. Was running the ac at a dead stop in 90 degree weather and the in dash temp gauge showed about 215 tops, 210 on average. Before the fan clutch I had one incident where the motor went up to 240 and I have the infamous 0331 head, that was stressful.