viscous fan test

psychoboy

05&06 Dodge Longs & Talls
I've searched the threads, and I'm not totally sure what should be happening when, but this is what I've gleaned:

When the van is cold, the blade should turn with just a hint of drag (it won't freewheel, but it won't really fight you, either), smoothly and with no noise.

When the van is warm, the fan should be harder to turn, but it should still turn.

When the van is hot, the fan should be nearly impossible to turn, since the clutch is fully locked up.


Basically, the hotter the motor, the more engaged the clutch is, and the more locked to the motor the fan is.


Since my expansion tank failed, and I replaced the radiator, I've never seen the gauge get past really warm, even pulling loads in the heat. The van has always felt like it was dragging an anchor, just a bit. like it had more to give, but something was keeping it from reaching full potential. I'm wondering if it might be the fan, dragging the motor and keeping it cooler than it would otherwise register.

Are my test assumptions correct? I can't just go "listen for the fan to engage" since I've never heard it engage (even back when the dirty radiator would let it get warmer), and if it's failed and locked up, it won't audibly change state, anyway.
 

obie

'04 long & tall passenger
When driving, it's quite obvious when it engages and disengages. Loud fan noise, or silent and only sound of diesel.
 

psychoboy

05&06 Dodge Longs & Talls
When driving, it's quite obvious when it engages and disengages. Loud fan noise, or silent and only sound of diesel.
Agreed, when it's engaged you hear it like a Semi transport truck starting from a stop on a hot day, whoosh
as noted above, if the clutch has failed and is partially or totally locked up, there will be no change, no difference in sounds, no "disengaged" to compare "engaged" to. My van is always loud, has always been loud. Surely there is some way of testing the action of the fan OTHER than listening for a change that will not occur if the tested item has already failed.

If you think the van has more to give, and you have not gotten the Green Diesel Engineering Tune, then you are right, it can give much more power with the Eco Tune or Hot tune https://sprinter-source.com/forums/showthread.php?t=30548
I have the tune, and while it has made a difference, it still feels like it's being hampered. When our 06 was new, and to this day (434,000 miles with no tune), it does not have the same "dragging a weight" feel to it.
 
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obie

'04 long & tall passenger
It will hamper mileage, and power some, sure, but when mine disengages, it's not like I feel a sudden unleashing of power. You are correct, if it never kicks off, it's locked. Have you ever had it off and laid it down? That's a big no-no.
 

psychoboy

05&06 Dodge Longs & Talls
it's not been off the van in the three years I've owned it. god only knows about the first seven.

is there a fairly reliable test for operation, short of trading it for a known good one?
 

obie

'04 long & tall passenger
Not that I know of, without removing it. Heat it up or cool it down, easier off of vehicle.
 

220629

Well-known member
I'm certain I have done this to mine, and my van does seem to run a bit hot. Is laying the fan/clutch "down" a certain way to wreck it?
Can you describe "a bit hot" better? Even under "normal" operation the Sprinter will not maintain the rock solid engine temperatures you may expect based upon Detroit iron gauges.

The mechanical cooling fan uses a fluid coupling with a bi-metal temperature sensor. The bi-metal controls where the fluid is allowed to distribute.

What I think that I know.

If the clutch/fan assembly is removed and laid flat the fluid can go where it isn't wanted which can affect the operation. That is not a problem with new clutch unit in the package. The fluid is trapped in the proper places until it is in service and comes up to operating temperature. Laying a used fan down may affect performance. It is best to keep the assembly in the same basic orientation as when installed (vertical).

You may notice that your engine driven fan roars when first started on cold mornings. Overnight the fluid pools in the clutch assembly. Until the fluid distributes from the fan turning, that pooled fluid will lock in the fan even when the temperatures are below the normal activation setting.

:2cents: vic
 

jackbombay

2003 158" shc
Can you describe "a bit hot" better? Even under "normal" operation the Sprinter will not maintain the rock solid engine temperatures you may expect based upon Detroit iron gauges.
On a 50* day climbing a pass by my house the temp raises to the midpoint between normal operating temp and the orange portion of the gauge, this is driving it somewhat gentle with a total van weight of ~7,000 pounds (there is a scale at the bottom of the pass).

Given the partial/light load and cool weather it just seems the temp shouldn't come up so easily, also, I have never heard the roar people are talking about when the fan does kick in.

I'll check it by trying to stop it with a rolled up newspaper at the top of the pass next time I head over the pass.

Thanks for the info!
 

Skippy

New member
Hi all,

On my 2005 T1N 2500, I've never heard the roar of the fan, and have occasionally gone into the red zone on hot days on a climb. Testing always showed that I could stop the fan even when engine was quite hot.

So I recently got a new fan clutch and installed, but so far I'm seeing same behavior as before. On a recent drive, the dash showed temperature around 240F, nearing the 'red zone'. I pulled over and tried stopping the fan with a piece of soft foam, and it easily stopped. Does this mean I received a non-functional viscous fan clutch ?
 

Midwestdrifter

Engineer In Residence
You could also have crap blocking the exterior or overthrow of the radiator. The clutch is warmed by the air through the radiator. A lack of air or coolant flow will prevent the clutch from getting warm enough to engage. An infrared camera might help.
 

Skippy

New member
You could also have crap blocking the exterior or overthrow of the radiator. The clutch is warmed by the air through the radiator. A lack of air or coolant flow will prevent the clutch from getting warm enough to engage. An infrared camera might help.
Good call. I was womdering about that. Radiator is only a year old so was thinking probably not too gummed up yet. I do have an infrared cam. Will be fun to look. Europarts is sending a different clutch so my fingers are crossed.
 

220629

Well-known member
Good call. I was wondering about that. Radiator is only a year old so was thinking probably not too gummed up yet. I do have an infrared cam. Will be fun to look. Europarts is sending a different clutch so my fingers are crossed.
If the radiator is that new, assuming the cooling stack was cleaned during the change, it's unlikely to be plugged with debris. A Europarts SD clutch I installed some time ago has been working fine. There have been reports of viscous fan units being bad out of the box (not necessarily Europarts).

Not that you asked...
Avoid the red zone in the temperature gauge. Some here believe, I'm one of them, that frequent excursions into the red zone can reduce the engine service life. Don't believe the myth that anything up to the 250F red zone is ok. A properly cooling Sprinter will not approach those temperatures except during extreme conditions. And I mean EXTREME, like fully loaded in desert temperatures while climbing a steep mountain. Just an opinion. My action point would be 235F. I have never seen that temperature in 12 years of Sprinter operation which includes towing.

:2cents: vic
 

jrod5150

Well-known member
Good call. I was womdering about that. Radiator is only a year old so was thinking probably not too gummed up yet. I do have an infrared cam. Will be fun to look. Europarts is sending a different clutch so my fingers are crossed.
What brand was the one they sent you? Myle? Vemo?
 

marklg

Well-known member
If the radiator is that new, assuming the cooling stack was cleaned during the change, it's unlikely to be plugged with debris. A Europarts SD clutch I installed some time ago has been working fine. There have been reports of viscous fan units being bad out of the box (not necessarily Europarts).

Not that you asked...
Avoid the red zone in the temperature gauge. Some here believe, I'm one of them, that frequent excursions into the red zone can reduce the engine service life. Don't believe the myth that anything up to the 250F red zone is ok. A properly cooling Sprinter will not approach those temperatures except during extreme conditions. And I mean EXTREME, like fully loaded in desert temperatures while climbing a steep mountain. Just an opinion. My action point would be 235F. I have never seen that temperature in 12 years of Sprinter operation which includes towing.

:2cents: vic
On a recent trip, fully loaded RV, through the desert, bright sunny 108F, up hill as fast as it could go (70ish) I got uncomfortable at 225 and slowed down before it hit 230. Fairly new viscous fan from Europarts SD, but a little concerned about it as it does not sound as noisy as expected.

Regards,

Mark
 

jrod5150

Well-known member
On a recent trip, fully loaded RV, through the desert, bright sunny 108F, up hill as fast as it could go (70ish) I got uncomfortable at 225 and slowed down before it hit 230. Fairly new viscous fan from Europarts SD, but a little concerned about it as it does not sound as noisy as expected.

Regards,

Mark
Brand?
 

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