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.

Click to expand...

Datatek said:

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

Click to expand...

kermit_rr said:

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

Click to expand...

RandyTravers said:

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

Thank you.

Click to expand...

RandyTravers said:

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

Thank you.

Click to expand...

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.

Click to expand...

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.

Click to expand...

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

Click to expand...

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.

Click to expand...