3.9 overheat in Classic

RandyTravers said:

Whilst stationary my 3.9 overheats
It has plastic fan on water pump.

Checked the readings on Rover Gauge and it steadily increases to 100°
Once I pull away it drops back down.
If I put blower on hot it cools down.

When the engine was previously in a Discovery it was fine.

Do I need to fit additional electric fans?

If thermostat was faulty it would get hot whilst driving and if heater matrix blocked that wouldn’t help either.

Any ideas please?

Thank you.

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Datatek said:

If the fan has a viscous coupling, it may that it has failed, a common problem.

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kermit_rr said:

Is the viscous fan working properly? Is the water pump working properly?

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RandyTravers said:

I could only imagine it is.
So perhaps the viscous is slipping?
And fan not spinning at correct speed?

Thank you.

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RandyTravers said:

I could only imagine it is.
So perhaps the viscous is slipping?
And fan not spinning at correct speed?

Thank you.

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Datatek said:

Try the newspaper test. Engine hot & idling, tightly rolled news paper, carefully push the newspaper into the fan blades, if it stops, the viscous coupling is fecked.

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Datatek said:

Try the newspaper test. Engine hot & idling, tightly rolled news paper, carefully push the newspaper into the fan blades, if it stops, the viscous coupling is fecked.

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kermit_rr said:

The viscous fan is filled with a silicone based oil (i think that's what it is) and eventually it leaks out meaning it doesn't lock up at much as it should.. eventually failing all together.
I noticed it on mine when the idle temp started to creep up. When i took it off the thread was damp and smelt

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norseman said:

As Data's advice is good. I had this problem with my old 5 series BM .. viscous fan clutch replaced, job done.
You shouldn't need additional 'lecky fans if your system is working properly. Another possibility is a clogged radiator, but if your temp. cools at speed that's less likely so try the 'rolled paper/mag' test first.

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