Viscous fan- how free is too free?

FlyingPete · Jun 30, 2015

I'm suspecting that the viscous fan coupling on my 19J is on its way out. The temperature gauge has been reading hot for some time, but I believe this to be inaccurate. The needle is normally fairly stable there so the thermostat appears to be doing its job.

With the engine off and cold, the fan can be turned by hand with a bit of resistance, and after a couple of rotations it frees up completely. When the engine is switched off after a run, the fan freewheels for about 2-3 complete turns before coming to a stop. My understanding is that this is normally a bit too loose, but of course the Landy fan could be different. The valve pin attached to the bimetallic coil on the front of the fan can be rotated back and forth with a screwdriver so it's appears to function.

Does this sound like the clutch is failing? If so, where's the best source of a replacement? I'd like to retain the belt-driven fan rather than messing around with an electric one.

Cheers

freelance · Jun 30, 2015

They don' t last indefinitely so probably time for a change

discool · Jun 30, 2015

With the engine cold the fan will only move one blade at a time, on start up it will sound like a turbine for the first 50 yards down the road because it's still locked-up, then it will go quiet until u get stuck in traffic on a hot day, then the fan will lock-up and sound like a turbine again.

Based on my disco as it has a viscous fan which has behaved as above from day one and still uses the original coupling so they can last a few years. Other normal cars I own or use seen to favour electric fans now.

Turboman · Jun 30, 2015

FlyingPete said:
I'm suspecting that the viscous fan coupling on my 19J is on its way out. The temperature gauge has been reading hot for some time, but I believe this to be inaccurate. The needle is normally fairly stable there so the thermostat appears to be doing its job.

With the engine off and cold, the fan can be turned by hand with a bit of resistance, and after a couple of rotations it frees up completely. When the engine is switched off after a run, the fan freewheels for about 2-3 complete turns before coming to a stop. My understanding is that this is normally a bit too loose, but of course the Landy fan could be different. The valve pin attached to the bimetallic coil on the front of the fan can be rotated back and forth with a screwdriver so it's appears to function.

Does this sound like the clutch is failing? If so, where's the best source of a replacement? I'd like to retain the belt-driven fan rather than messing around with an electric one.

Cheers

Bit hard to say without feeling the fan myself, but that doesnt sound right. The couplings are widely available, paddock will have them and all usual suspects. I wouldn't fit electric, viscous is better. And get an accurate temperature gauge, overheating can be a serious issue on these

discool said:
With the engine cold the fan will only move one blade at a time, on start up it will sound like a turbine for the first 50 yards down the road because it's still locked-up, then it will go quiet until u get stuck in traffic on a hot day, then the fan will lock-up and sound like a turbine again.

Based on my disco as it has a viscous fan which has behaved as above from day one and still uses the original coupling so they can last a few years. Other normal cars I own or use seen to favour electric fans now.

I don't know about your disco, but the viscous fan on my 19j doesn't make any noise that is noticeable above the engine sound. None, under any conditions.

And I really wouldn't recommend fitting electric fans on 19j, most who have end up taking them off again!

Datatek · Jun 30, 2015

FlyingPete said:
I'm suspecting that the viscous fan coupling on my 19J is on its way out. The temperature gauge has been reading hot for some time, but I believe this to be inaccurate. The needle is normally fairly stable there so the thermostat appears to be doing its job.

With the engine off and cold, the fan can be turned by hand with a bit of resistance, and after a couple of rotations it frees up completely. When the engine is switched off after a run, the fan freewheels for about 2-3 complete turns before coming to a stop. My understanding is that this is normally a bit too loose, but of course the Landy fan could be different. The valve pin attached to the bimetallic coil on the front of the fan can be rotated back and forth with a screwdriver so it's appears to function.

Does this sound like the clutch is failing? If so, where's the best source of a replacement? I'd like to retain the belt-driven fan rather than messing around with an electric one.

Cheers

It should be hard to stop the fan when the engine is hot, standard test is a tightly rolled newspaper thrust into the blades with engine hot an idling (mind your fingers). If the fan stops, it's fecked. A duff RAD not getting hot in the centre can also cause the viscous to fail to lock up.
If you car has the supplementary electric aircon fans, these can be modified to provide back up engine cooling, I say this having no idea what a 19J is

FlyingPete · Jun 30, 2015

Looks like a new viscous coupling will be added to the shopping list then! Sounds like the fan isn't really locking up at all. The radiator is nearly a year old so that should be fine. I'm assuming that given the gauge needle is relatively stable (at the top of the scale) it's the gauge that's wrong rather than overheating- in normal driving there's enough ram air that the broken fan shouldn't be having an effect.

Datatek · Jun 30, 2015

FlyingPete said:
Looks like a new viscous coupling will be added to the shopping list then! Sounds like the fan isn't really locking up at all. The radiator is nearly a year old so that should be fine. I'm assuming that given the gauge needle is relatively stable (at the top of the scale) it's the gauge that's wrong rather than overheating- in normal driving there's enough ram air that the broken fan shouldn't be having an effect.

Most diesels will run without a fan as long as they keep moving. I binned the viscous on my P38 diesel a while back, just the aircon fans are enough even when it's 35c as it was today going to town.

FlyingPete · Jun 30, 2015

That's the reason why even a fixed fan will work acceptably- at speed the torque required to drive the fan drops right down, even though it's still being driven at engine speed. That's why electric fans look great on a dyno. I expect a (working) viscous fan will just be spinning in the breeze a lot of the time.

Turboman · Jun 30, 2015

Datatek said:
It should be hard to stop the fan when the engine is hot, standard test is a tightly rolled newspaper thrust into the blades with engine hot an idling (mind your fingers). If the fan stops, it's fecked. A duff RAD not getting hot in the centre can also cause the viscous to fail to lock up.
If you car has the supplementary electric aircon fans, these can be modified to provide back up engine cooling, I say this having no idea what a 19J is

I agree that the fan is knacked!

I have only ever seen one vehicle with 19j and aircon, and that was pics posted by some crazy Indian that had built it himself!

Maybe there are others but that is the only one I have seen.

19j (2.5td), is an indirect injection 2.5na, with a turbocharger just bolted on the manifold. Gives a power increase from c.65 horse to c.85 horse.
Unfortunately it can also seriously compromise reliability, a number have self destructed!

Datatek said:
Most diesels will run without a fan as long as they keep moving. I binned the viscous on my P38 diesel a while back, just the aircon fans are enough even when it's 35c as it was today going to town.

Sorry mate, you know a lot about rangies and electronics, but not much about 2.5td. No fan would be a recipe for disaster.

With no intercooler the compression heat from the turbo has nowhere to go but into the engine and the oil, which can lead to the hotspots that can crack heads and blocks, or melt pistons.
The fan and cowl will have plenty of work to do!

FlyingPete · Jul 1, 2015

So I took the coupling off to do some fairly crude testing. The bimetallic coil that controls the thing only shows any sign of movement when directly heated over a gas hob. In boiling water (the air coming off the radiator will never be any hotter than the coolant) no movement at all. So basically it's stuck in the cold position. New viscous coupling on its way, and going to do the water pump while I'm at it as well

Datatek · Jul 1, 2015

Turboman said:
I agree that the fan is knacked!

Sorry mate, you know a lot about rangies and electronics, but not much about 2.5td. No fan would be a recipe for disaster.

With no intercooler the compression heat from the turbo has nowhere to go but into the engine and the oil, which can lead to the hotspots that can crack heads and blocks, or melt pistons.
The fan and cowl will have plenty of work to do!

I stand corrected, had a lot of turbo diesels, removed the viscous on all of them and used electric without problems

Turboman · Jul 1, 2015

Datatek said:
I stand corrected, had a lot of turbo diesels, removed the viscous on all of them and used electric without problems

Tdi will run all day without a fan.

19j are a different kettle of fish, cooling and lubrication systems need to be 100% for the thing to have a chance of survival!

OP, I think changing the coupling and water pump is a good plan, doubt if you will regret doing that!

FlyingPete · Jul 21, 2015

So the new fan clutch came and has been fitted for a couple of weeks now. Big difference- you can now hear the fan for the first minute or so after a cold start, then it settles down. Sat at traffic lights etc you can hear it slowly pick up speed, and switching off after a motorway run, it might as well be a fixed fan- very little movement.

Water pump is still to do, but that can be a job for when it's time for a service.

Viscous fan- how free is too free?

FlyingPete

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