940 LPT Idle Woes... Help!

[Dirty Rooster]

Originally Posted by TonyS9

The viscous coupled fan will always 'run', but it doesn't push hard. In fact it rarely does except maybe after stilling at idle on a really hot day, then when you rev you can hear it sounds like a bus, but only for about 30s or so until the air flow cools it down.

I have a normal viscous coupled fan,
but this is the old fan from my previous engine and works great : i.e. good warmup, no temperature issues winter or summer.

The fan that was on this (replacement) engine was 'jammed' fully-on at all times and killed a radiator and an oil cooler when it dramatically died, bits of blades scattering like shrapnel from a grenade.

I have an electric fan in the workshop but don't want the hassle of fitting it ...

I too doubt Scooby's 15% figure, however since ALL modern eco-obsessed engines use an electric fan I'm sure the advantage is non-negligible.

[Laird Scooby]

Originally Posted by Dirty Rooster

I too doubt Scooby's 15% figure, however since ALL modern eco-obsessed engines use an electric fan I'm sure the advantage is non-negligible.

This isn't worded very well so don't take it the wrong way but you can doubt what you like, that's the economy i'm getting from it and much improved since removing the viscous fan.

I can't afford to throw money at the petrol tank and guess what i'm getting to the gallon and also can't afford to run out because i've miscalculated.

I think Tony hit the nail on the head because most of my runs are short, however as stated i have had some seriously good figures from mine. That said i've had some even better figures from my 827s, up to 43mpg on one occasion.
I've also had my 760 down to 8mpg on a good day when it had a hidden fuel leak.

Sorry if that comes across as slightly aggressive, it's not meant that way, just having amental block at the moment where my usual way of explaining something with a bit more diplomacy is.

[LPTJoe]

Originally Posted by Dirty Rooster

I have a normal viscous coupled fan,
but this is the old fan from my previous engine and works great : i.e. good warmup, no temperature issues winter or summer.

The fan that was on this (replacement) engine was 'jammed' fully-on at all times and killed a radiator and an oil cooler when it dramatically died, bits of blades scattering like shrapnel from a grenade.

I have an electric fan in the workshop but don't want the hassle of fitting it ...

I too doubt Scooby's 15% figure, however since ALL modern eco-obsessed engines use an electric fan I'm sure the advantage is non-negligible.

Right, given this is now a fan centric topic, I suspect my fan may well be jammed permanently on too... How would I go about checking if that's the case?

[Laird Scooby]

Originally Posted by LPTJoe

Right, given this is now a fan centric topic, I suspect my fan may well be jammed permanently on too... How would I go about checking if that's the case?

First, there's the way of checking if it's completely jammed, try turning the fan by hand (engine off!) and if it is extremely hard/impossible to move then it's most definitely jammed.

Next is temporarily remove it - 4 nuts/bolts on the pulley, you should be able to wriggle it out past the cowling on most models, if you can't, depending on the model of radiator, it's either 2 nuts/bolts at the top and 2 locating lugs at the bottom or 4 nuts/bolts, two top, two bottom.
Once the fan is off, take it for a drive and if you think you've gone deaf, it's almost certainly jammed.

Like Tony described earlier, at first start up it should roar for the first 30 seconds or so then go quiet. It's difficult to know if it is quiet while you're driving normally as it mixes with other noise, the acid test is removal. If you think you've gone deaf then it's making noise that you don't realise until it's gone.

There are other test methods, those are the ones i use.

[TonyS9]

I can stop my fan with my hand with the engine running, protecting my hand with a rag and slowing it down gradually, but it does vary between vehicles and some are nearly impossiblem or maybe its just different weather.

This is why I think it does have a drag and cooling effect at cold idle.

Certainly it should move freelyish by hand with the engine off.

[LPTJoe]

Right, checked it last night when cold (8 hours since the car had ran) and the fan moves freely in either direction, albeit with an amount of resistance as the clutch fluid is clearly viscous/thick when cold.

Looks like all is well, it seems the fan is just noisier than any other cars I've owned and will take some getting used to...

[TonyS9]

Originally Posted by LPTJoe

I did try to politely bring things back on topic, see post #32



I no longer have the problem, I kindly refer you once again to post #32. Clearly you were so caught-up in the 'whilrlwind' of Fan-gate that you completely missed the fact that my issue is now resolved....

All I'm saying is maybe, just maybe, it's time to start a fan-centric thread of your own chaps? That way you can both debate this to your hearts content whilst remaining on topic and ending the de-railing of this one, which is, on the whole, intended to be an idle based topic

I must admit I did get confused with the number of threads on idle problems, nothing to do with fan gate.

But I am not confused enough to get a room with Laird Scooby, which is what I was subtly referring to as your not so polite suggestion

[Derek UK]

As with the 240, the startup whoosh is due to high-speed air being pushed back through the gap between the fan blade tips and the cowling. If you remove the cowling (experimentally) you won't get the whoosh but it pulls much less air through the rad so you need the cowling. As well as the thermostatic fan becoming fixed if the airflow gets too hot it will slip after about 3k revs to reduce power absorption as well as noise.