Disco 2 How stiff should viscous fan be? TD5

When hot

Temperature went over 100c

pipes are all hot, reasonable mixture of coolant

Fan would spin about 1/4 turn with a flick.

The reliable way to check it is to try to stop it wilt a rolled up newspaper when the engine is hot and running... if you can it's fubar

It whacked hard!

Will watch temperatures over the week

If u can spin the fan around when it's cold i.e. after standing over night then it has a problem, from cold it will only move about one blade at a time, you should hear a change in the sound of the fan within a minute or so of starting the engine when the fluid has circulated within the coupling.
That initial sound fan sound will return "if and when" the fan coupling locks up with a hot engine as most of the time it's not locked.

I don't know if the fan is something that u can be hear over with a clatter of a Diesel engine, but it can heard if the engine is petrol as it sounds like a turbine.




Sent from my iPad Air in Malta.

Sometimes when I start off I can hear it, but not always.

Will see how it behaves on a trip to Bath next weekend

MJI said:

Sometimes when I start off I can hear it, but not always.

Will see how it behaves on a trip to Batch next weekend

Click to expand...

Hi
I fitted and engine watchdog to keep a keen eye on the head temp after recently replacing the cylinder head. On a recent trip on a hot day with the caravan on the back the temp on the Watchdog went above 110c. On then return journey things cooled down as the weather was a lot cooler but the coolant was still up in the 90's.
I set about seeing what was amiss. Having already replaced the water pump I next looked at cooling radiator. I knew there was a slight weep so replaced it. The cooling seemed more stable (using Nanocom in Instrument mode). I thought at 120,000 miles it might be a good thing to replace the viscous cooling fan, even though it seemed to be ok. What a difference! The fan can be heard at startup and sounds like the roar of a jet plane until the viscous fluid inside the fan hub settles down after about 2 minutes. It can be heard cutting in and out dependent upon the outside temp. With the caravan on the back today and giving the engine some boot the coolant temp never went above 86c. Normal running is around 84c
In the two years I've had my Disco I've never heard the fan before and so assumed it was working as it should, I've now learned different.
I'd recommend changing the fan if in any doubt, if it's working as it should you should easily hear it above the engine noise of the TD5. I bought a Britpart one which may, or may not be a bit more noisy than the manufacturers one but I'm sure it should still be heard.
Hope this helps others.