Disco 2 TD5 - Fan cutting in at 2000rpm from cold.

Hello fellow LZders. A new development in my Disco 2 TD5 journey.

About a month ago, a routine drive had an interesting turn. A fan (at least that's what I think it is) cut in whilst I was tooling about. I thought it was just the viscous fan cutting in as things got a bit warm. It had never done it before. But, it does it every time I drive since, with the engine cold or up to temperature.

It's really, really noisy. It seems to cut in about 2000rpm and then the pitch just increases, like it's getting faster and faster as the rpm rises. I've checked the coolant and it's fine. The temperature gauge seems to operate normally too and the coolant level is fine too, thought when I checked it after the first few times, it was a bit low - think I may have a leaky core plug.

It only cuts in when I'm actually driving and it I raise the rpm when stationary, it doesn't cut in, so I'm having a hard time actually witnessing it (other than the audible whine as I drive). Everything else seems normal and it doesn't sound like the whistle of the turbo - which is always there in the background, but relatively quiet.

Suffice to say, I don't think it's normal and before I go poking around too much, I thought I would check in and see if anyone has seen this before or any advice on things to check first - such as the right search terms to use to narrow the results on here

Much appreciated!

AFAIK the turbo does cut in at about 2000 revs, and since the noise starts then and increases with engine revs, I would definitely be looking at the problem being turbo related. I'd be checking for leaks in the air pipes between the turbo outlet and the inlet manifold, including around the intercooler first off.

Oh yikes! I was hoping it was just a stuck switch for the fan...I'll be taking the covers off and have a good look at the hoses! It did cross my mind, but as performance didn't seem to be suffering, I mentally ruled that out. Thanks @brian47.

fan has a viscous unit its possible its failed so locking when it shouldnt

jamesmartin said:

fan has a viscous unit its possible its failed so locking when it shouldnt

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Thanks @jamesmartin. That does sound plausible - hadn't thought of that.

The "classic" way of testing is to try to stop the fan with a rolled up newspaper when the engine is cool (but let it run for a minute or two after starting as the silicone fluid needs to spread itself around). This should be easily possible if the viscous unit is freeing up OK.

So, it took me until yesterday to get under the bonnet and have a good look around. Turns out the hose between the turbo and the inter-cooler has two 2" long tears in it. So, I think I've found the source of the problem! Thanks for the advice chaps. I think I'll be replacing all the hoses in one go.