P38A Viscous fan

Hi all
I think i may have a problem with the viscous fan on my P reg P38 diesel
The engine got hotter than normal yesterday so thought i would investigate
The fan seems pretty stiff to turn by hand when the engine is off
Get the engine up to temp but the fan still spins slowly and i can easily stop the fan with a newspaper
I’ve read on here air con fans can help with cooling but my P38 doesn’t have air con
Any help greatly appreciated

Sounds like you need to replace the viscous coupling!

+1

They are pricey.
should shred the paper when warmed up.

Some choose to use Data’s air con mod that uses an electric fan instead.
Many have done it and works fine even towing etc

I prefer the viscous myself but take a look how much they are first

Main thing you should consider is the water pump and has it been changed. If it’s on the original and It blows will make an ex spensive mess.
Ask me how I know

oakey said:

+1

Click to expand...

+2

This is the V8 one, no idea if the diesel is the same. https://bearmach.com/viscous-fan-coupling-err4996r

PGG101290 is the diesel fan and coupling.

My type below you can take the fins off the coupling so can just change the coupling will save few quid.

If you go to take the coupling off remember it’s a left hand thread. Some are easy some are really stuck on there.

RangeRoller dt said:

PGG101290 is the diesel fan and coupling.

You may be able to get just the coupling and save yourself few quid, few little bolts swaps over

If you go to take the coupling off remember it’s a left hand thread. Some are easy some are really stuck on there.

Click to expand...

Eighty quid ish. I was expecting more, tbh. Of course, you could pay four hundred for a genuine LR one.

Marshall8hp said:

This is the V8 one, no idea if the diesel is the same. https://bearmach.com/viscous-fan-coupling-err4996r

Click to expand...

Got a feeling the v8 has opposite thread. The diesel is reverse thread.

Viscous will start up with a roar as it will be locked, after maybe 30 seconds it will start to quieten down as it slackens off. As the engine starts to get hot (hold it at 2000rpm for a while) and the temperature starts to climb the viscous will start to make more noise as it locks up. At this stage you won't be able to stop it with a rolled up newspaper. Or shouldn't be able to.

Other possibilities are air lock (is it topped up and bled properly?), water pump, thermostat and rarely a cracked head. If you don't have a metal impeller then worth changing that and the stat while you are about it.

You’ll hear it roar like brians a tank when it’s locked

RangeRoller dt said:

Main thing you should consider is the water pump and has it been changed. If it’s on the original and It blows will make an ex spensive mess.
Ask me how I know

Click to expand...

Can I tell if mine has a metal or plastic impeller without disassembly?

No. You pull it out and have a look. Not hard or take too long. Viscous & belt off and you unbolt the whole pump, have to burp system and top up you will lose lil bit. New o ring on refit. Bit of card or something to protect your rad as it’s tight in there and easy to bump.
Try look through receipts if you have them.

There’s metal coloured plastic ones and shyte tin like crap ones with funny edges to be weary of. Il get you the part number if you need proper one

If yours has been renewed with new plastic unit that’s fine, some say they work better.

after 120,000 miles your on borrowed time til it breaks. Mine went at about 128,000m
The old brittle plastic goes to bits and you have to get every piece out, since the pump is spinning about 120,000 rpm the bearings go and it ejects out the front through the rad taking the viscous with it

Good thing about metal pump is only £40 and if it does go (nobody’s has) no shrapnel lost inside the block to doom your engine forever.
See some people now and again with P38 diesels that have strange incurable cooling issues ; now you know why

Grrrrrr said:

Got a feeling the v8 has opposite thread. The diesel is reverse thread.

Viscous will start up with a roar as it will be locked, after maybe 30 seconds it will start to quieten down as it slackens off. As the engine starts to get hot (hold it at 2000rpm for a while) and the temperature starts to climb the viscous will start to make more noise as it locks up. At this stage you won't be able to stop it with a rolled up newspaper. Or shouldn't be able to.

Other possibilities are air lock (is it topped up and bled properly?), water pump, thermostat and rarely a cracked head. If you don't have a metal impeller then worth changing that and the stat while you are about it.

Click to expand...

V8 is left hand thread.

Thanks for all the replies fellas, has anyone got a link for the decent water pump to get as i think i’ll change that whilst i’m changing the fan
Thanks guys

I got mine from Island 4×4 .

tomcat59alan said:

I got mine from Island 4×4 .

Click to expand...

+1 ^^^^^^^^

RangeRoller dt said:

PGG101290 is the diesel fan and coupling.

You may be able to get just the coupling and save yourself few quid, few little bolts swaps over

If you go to take the coupling off remember it’s a left hand thread. Some are easy some are really stuck on there.

Click to expand...

Not with the BMW viscous you can't. Have seen them fitted with Disco fans, then you can indeed fit a new viscous hub to the old fan.

This water pump?
https://www.island-4x4.co.uk/water-pump-stc2192g-stc3342g-metal-impeller-p-1389.html

goreden said:

This water pump?
https://www.island-4x4.co.uk/water-pump-stc2192g-stc3342g-metal-impeller-p-1389.html

Click to expand...

Yup.