Running a TD5 without a viscous fan?

jamesmartin said:

viscous is better imo unless your deep wading

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Why?

Not trying to be an arse, just interested in your rationale.

Balbas said:

Why?

Not trying to be an arse, just interested in your rationale.

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less thermal shock

I removed the visco last winter and that was really great for normal cruising, quicker on temperature and no problem with oerheating.

But then I had to go up on the mountains and was stuck in traffic an the car overheated and went into limp mode.

way to unsecure for me.

jamesmartin said:

less thermal shock

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I'll qualify this by saying that I'm not an engineer, nor am I a mechanic.

If there is a thermostatically controlled fan (be it on a viscous coupling or electrically driven) drawing air through the radiator, and the rest of the cooling system is in good order, then where does the thermal shock come from? As I understand it:-

When engine starts to get hot
1) stat begins to open (doesn't just bang open fully - that would cause thermal shock) allowing water from the rad to be pumped around the block
2) fan starts to draw air through the rad, cooling the coolant.

No fan I've ever seen would cool the coolant sufficiently to refrigerate it.

Or am I missing the obvious?

Thinking about it, it's not just my old series 2 days which make me think it might be a good idea. I also have a Triumph Spitfire with a cooling system best described as 'marginal'. Accepted wisdom is to get rid of the engine driven fan and put a modern electric thermostatically controlled 2 speed fan on instead. And I used to commute on a Ducati with a marginal cooling system (and being Italian the wiring would catch fire if it got too hot!:lol bikes have the added difficulty of tight packaging and small radiators combined with high power outputs for their capacity, co can get hot really quickly. Although it had an electric cooling fan, the fix was to use a different fan switch to get the fan started on the business of cooling things down sooner.

I'm not hard against using a viscous fan, but I'm interested to know why some clearly intelligent and thoughtful posters think a viscous fan is the best answer. And if anyone tells me 'Landrover employed some very clever people and spent a lot of money specifying a viscous fan therefore it is the best' I'll point to the rear chassis rails and ask if the specified steel used to make those was also the best.... I don't think I'm cleverer than an automotive engineer, but I do think that maybe as I am not constrained by cost to the same degree and that as I know more precisely the environmental conditions I am likely to find myself in that perhaps it is possible to rid myself of what could be seen as a compromise.

Further to my last, the switch in a viscous fan isn't controlled by the coolant temp, but by the air temp - as far as I can see it is in effect a bi-metallic strip controlling a simple fluid valve. I'm struggling to see how an electric fan controlled by a thermostatic switch in the coolant could be 'worse' (unless the switching temperature was wrong of course).

Still happy to be convinced by a compelling argument though.

I'm not that knowledgeable, but the viscous fan seems to be spinning all the time, pulling some air through the rad and over the engine even if the coupling is barely engaged (ok wafting might be a better term!). A leccy fan does nothing until the thermostat triggers it, then wham! Full blow

However, suddenly dunking the Landy in cold water would generate thermal shock anyway wouldn't it?

the viscous fan is removed by a lot of off roaders in the td5 model as the fan blades act as a paddle throwing water onto the ecu box under the bonnet
no other reason !!!
stick with the viscous fan. the electric Chinese **** will let you down

Where as the cooling of the rad is infinitely variable with a viscous coupled fan, an electric fan is either off or on but on only when the coolant temperature is higher than the normal running coolant temperature, Kenlowe suggests a setting of 5c above, that makes the engine bay worryingly hot before the fan cuts-in ...

That's my experience of course with a Kenlowe fan fitted to a 2ltr Ford 4 cylinder Pinto engine although so far I haven't had problems with the extra heat, then the fan only cuts in in traffic.

Balbas said:

Oh really? Back when I had a series 2 (almost 20 years ago now) kenlowes were all the rage. Why are they considered 'not good' nowadays? If they're moving air though the rad core, then surely they're doing the biz? Especially if the TD5 cooling system is suitable for crossing desserts and the like?

As a partial aside, I drove a 300tdi powered 110 around Kuwait and Iraq for a bit and it never once missed a beat. I had absolute confidence in that wagon even in near 60 degree centigrade heat. So I know the standard cooling systems are well up to the job and probably vastly over specified for the uk.

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well you know the answer then, so you try it and do it, then put the result up here and ley us all know, but you bought the vehicle with out one, not us, so why no fan??? maybe they forgot to put it back on, maybe it's been up to it's windscreen in mud n water? you asked for peoples opinion and JM told you his, his is good enough for me!

Not just TD5s but applicable to virtually all Tdi with intercoolers.

You need the viscous fan to draw ambient through the intercooler and cool the intake temps, this is double edged, higher intake temps = higher combustion chamber temps, leading to hotter exhaust gasses, hotter exhaust gasses tend to reduce life span of turbos, head gaskets and life of the oil in the engine as the higher temps break it down faster.

discodrivercumbria said:

well you know the answer then, so you try it and do it, then put the result up here and ley us all know, but you bought the vehicle with out one, not us, so why no fan??? maybe they forgot to put it back on, maybe it's been up to it's windscreen in mud n water? you asked for peoples opinion and JM told you his, his is good enough for me!

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Not having a pop, I don't do things just because someone says so. I want to know why they say so.

dieseldog69 said:

Not just TD5s but applicable to virtually all Tdi with intercoolers.

You need the viscous fan to draw ambient through the intercooler and cool the intake temps, this is double edged, higher intake temps = higher combustion chamber temps, leading to hotter exhaust gasses, hotter exhaust gasses tend to reduce life span of turbos, head gaskets and life of the oil in the engine as the higher temps break it down faster.

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That does make some sense. And tilts me back towards putting a viscous fan on.