New fan clutch - break in or broken?

[JHZR2]

I knew my fan clutch on my 1991 350sd was not working right because when I would run the air conditioner in hot weather and traffic, the engine temperature will keep up past where it should be.

It was the original made in 1989. 208k miles.

Sometime back, I bought a replacement fan clutch, it was not OEM, but was a brand (that I don’t currently recall) that I found had gotten good reviews on a dodge Cummins forum, and was potentially US-made. All of the standard aftermarket name brands looks to be Chinese knock, offs anymore, and the fan clutch design for the original aluminum fan was supposedly NLA.

Unfortunately, the clutch that I ultimately received was a Chinese made one, and return shipping wasn’t worth it. So I just installed it.

It is slightly thicker than the original one, but it bolted right up to the fan and onto the engine. I’ve driven it around 40 miles, and it sure seems to me like it is just constantly on. I know what the fan clutch sounds like on my dodge ram Cummins when it cycles on and off. The original Mercedes fan clutches, when working properly, seem to be silent. This one sure sounds to me like it is always permanently on.

Maybe that’s not such a bad thing, since the temperature gauge stays rocksolid stable And the air conditioning is blowing beautifully for being relatively warm and very humid.

But I am generally curious, since my understanding is that fan clutches have two chambers and oil that migrates between them, if there is some sort of a break-in or cycle that is required before it actually runs properly and cycles itself.

Or maybe it’s just Chinese junk, and I should replace it with the upgraded plastic blade fan and OEM fan clutch like my W124 Pats.

Any experience??

 

[spasm3]

When i replaced the fan on my previous avalanche, i went GM oem. I read several reviews online about another brand clutch keeping the fan on constantly, while that did keep the air moving over the rad, it wasted fuel at speed instead of clutching. IIRC Hayden was the brand that reviews claimed didn't clutch as it should.

 

[blufeb95]

Is the new clutch a standard duty or a heavy duty clutch?

 

[spasm3]

Rock Auto shows a Vemo fan clutch, that claims to be German made.

 

[Dino01]

For the older diesels (went through the same debacle with my old 95 E300 diesel) I’ve found only the Mercedes dealer-sourced clutches made by Horton work correctly.

I tried Sachs, Behr, and even Febi-Bilstein; none worked properly until I paid the piper for the MB/Horton. Some were always engaged and others not enough so temps would rise rapidly and ac performance suffered in temps above 90-95f.

 

[2strokeNorthstar]

For the older diesels (went through the same debacle with my old 95 E300 diesel) I’ve found only the Mercedes dealer-sourced clutches made by Horton work correctly.

I tried Sachs, Behr, and even Febi-Bilstein; none worked properly until I paid the piper for the MB/Horton. Some were always engaged and others not enough so temps would rise rapidly and ac performance suffered in temps above 90-95f.

Same experience on my 90s BMWs. OEM is the way to go. Something as simple as the oil being too thick will make them engage much more often and be noisy. That's actually a "fix" on old Landcruisers. Drain the oil and fill with a higher CST silicone fluid. Supposedly places like Australia use thicker fluid.

 

[RoadDukie]

I would certainly give it some more miles before chucking it. Especially if your understanding is true about the break-in period. All you have to lose may be a little diesel fuel if it doesn't settle down.
As mentioned, it sure won't hurt the cooling system.

 

[SwampSurvivor]

Is it a replacement for your car or a Dodge truck with a diesel?

If it sat for a while, it could take some time for the viscous fluid to distribute. Nothing too wrong with a roaring fan, though. I swapped in the wrong fan clutch on my cherokee and it's always roaring. But it's good for temperature.

 

[Trav]

I would not be in a hurry to replace it, it sounds like it is working as it should. This is a simple bimetallic viscous fan with no solenoid so there is no on/off it is just a gradual increase as the metallic spring or strip expands, the new one seems to have a larger fluid chamber so it may have more residual torque and is a stronger fan. If it turns freely (not spin around like a pin wheel just not too stiff) when cold and is harder to turn when warm it is working properly.

Easy to test, put it in the fridge and turn it then warm it with a hair dryer not a heat gun in the front of the fan and it should stiffen up.

 

[dumkid]

Give it a few weeks and see if it ever stops roaring. My dad used to drill a few holes and put a bolt through his fan clutch, so it was always 100% engaged on his off road vehicle.

 

[SwampSurvivor]

Give it a few weeks and see if it ever stops roaring. My dad used to drill a few holes and put a bolt through his fan clutch, so it was always 100% engaged on his off road vehicle.

That's a great modification for offroad vehicles. I enjoy watching on facebook groups where someone gets an older, unmaintained Jeep and has overheating issues. Then immediately converts it to electric fans and has the overheating issue get worse. Ultimately, the fix is always convert back to mechanical and fix the original cause of the overheating problem.

If you're doing anything above idle, you just can't beat the CFM of a locked up fan clutch.

 

[wrcsixeight]

I'd laid my fan clutch on its back one time for a few days, and then when reinstalled it roared, seemingly locked up.
Took a few hot cold cycles until it behaved normally.

I am of the opinion that many electric fans are installed way too close to the radiator fins, when not moving.
The restriction of the fins /tubes causes stalled blades when there is not airflow from a moving vehicle assisting the airflow.
More fan rpm makes it worse.

 

[camrydriver111]

Does it at least disengage at high rpm?

 

[JHZR2]

I'd laid my fan clutch on its back one time for a few days, and then when reinstalled it roared, seemingly locked up.
Took a few hot cold cycles until it behaved normally.

I am of the opinion that many electric fans are installed way too close to the radiator fins, when not moving.
The restriction of the fins /tubes causes stalled blades when there is not airflow from a moving vehicle assisting the airflow.
More fan rpm makes it worse.

Yeah this clutch sat flat for a very long time. I have about 300 miles on it.

In 90 degree humid weather temperatures are rock solid stable and ac is cold enough to need to turn it down.

 

[JHZR2]

Update to this. Fan clutch failed and the bearing is seized. Caused the bolt to back out and fan to fly off. Destroyed radiator.

Attempting to use a $50 Chinese clutch has turned into a $500+ error…

 

[Marcozi]

The installation of aftermarket cooling system parts is strictly verboten!