Blue fan clutch question (1 Viewer)

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Nov 18, 2019
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I did the RavenTai temp gauge mod and have been noticing temperatures creeping up towards the bottom of the red (about 210 to 215 deg) when sitting in traffic or going up hills, either at freeway speed or crawling. Outside temperature is around 80 deg so nothing very hot.

I checked my fan clutch and the PO had installed an aftermarket unit, so I bought a new Aisin blue hub fan clutch and replaced the fluid with 15k cst silicone oil (I put in a little over 40 mL). I didn't mod the turn-on temperature, but did verify the thermal spring was opening and closing at around 105-110 deg. I also replaced my radiator cap with a new OEM.

With the old fan clutch, I heard a distinct "roar" at startup. The blue fan clutch has no roar on startup, and I can't hear it turning on and off. It also doesn't seem to be cooling any better (maybe even a little worse) than the aftermarket, and it doesn't seem to be pushing a ton of air. But on the other hand, the new clutch doesn't freewheel, and seems to have plenty of resistance when I turn it by hand. However, today my engine temperature still climbed up to just under the "red" when crawling up a steep hill. When I turn off the A/C and turn on the heater then the temp drops back down quickly.

Does the lack of roar on startup, and the fact that I can't hear the fan clutch turn on and off, mean that the new blue fan clutch is not functioning properly? Could my belts be too loose, or what would be the next step after replacing fan clutch and rad cap, a new radiator? I'd like to get the cooling system rock solid for off roading. Thanks
 
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flintknapper

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Mine doesn't 'roar' at start up...but I can hear it for sure. Mine took 48ml to fill...so you might be a bit shy there. Don't know how much difference that would make however.

How old is your radiator and what type is it?
 
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My radiator appears to be aftermarket and not super old--the aluminum fins facing the fan are still clean and shiny. I don't see any markings or stickers on it though. Coolant is bright green. The PO said he replaced the thermostat, not sure what brand was used though.
 
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When you're draining the old fluid out, i found that it takes about 24 hours for all the old fluid to drain out before you'll want to try refilling it. I checked the amount of fluid mine would need by draining all the old fluid into a large syringe. Then i refilled mine with 50 ML of 20000k fluid, the exact same amount collected in that syringe.
 
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Is that at room temp or heating in the oven at 170 deg?
I live in Arizona and did mine in the summer time with a room temp inside my garage of 108. Even with it being that warm i still let is drain for 24 hours just to make sure i got as much of the old fluid out as possible.
 
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I got out about 30 ML of old fluid, plus there was a little more left on the surface on the pan. Is it possible I overfilled the clutch and it and now is always on? You can hear it go on and off right? I can't, it seems to always be on, but it doesn't "roar" or seem like it is pushing that much air. But it doesn't freewheel either, so I'm a little confused.

P. S. I just bought a new radiator off Amazon, but do want to make sure the fan clutch is working too.
 
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What i found when i did my fan clutch, in order to get as much fluid out a possible you can't get in a hurry.

Another thing i did to help get as much fluid out as possible. I stood both half's of my fan clutch on end inside a funnel that drained all the old fluid into a syringe, that way i could measure just how much fluid i was able to recover.

When i start my truck first thing in the morning the fan clutch will "roar" for about 1 or 2 minutes. After that the RPM's will drop down to about 650, to 700 and the roar goes away.
 
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georgia
My modified(wits-end)blue hub fan clutch does not roar on start up,but is definitely pulling more air through the radiator when parked@650rpm engine speed based on temps and the aux fan blades moving faster than before.my engine is running 10 degrees cooler
 

77mustard40

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Not to hijack but I installed a new blue on my 80 a couple of months ago when I did the oil pump cover seal, the old one was dead. It’s not modified but I’m wondering if I should before summer sets in. Years ago I did the clutch on my 40 chasing overheating issues and replaced the fluid with 15K, overheating solved. My 80‘s fan is audible on cold starts for a minute or so and can also be heard can be heard on occasion when driving. I haven’t had any temp issues with it yet and we’ve had a couple days in the high 90’s. What do you guys think?
 

landtank

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The roar on startup comes from the oil inside the clutch settling at the lowest point with in the clutch. This oil is split between the control side and drive side of the clutch and as such will be sheared and moved to the control side of the clutch where it will then be metered back to the drive side as needed based on the air temperature influencing the temp spring on the front of the clutch assembly.

All viscous clutches should roar on startup. The amount of roar depends on the CST of the oil and the duration of the roar depends on the volume of the oil and the engine RPMs.

Before the first startup of the day check the resistance of the clutch by turning the fan by hand. There should be a good amount of resistance.
 

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