Temp gauge not rising

I can sit and idle all day and the temp gauage won't climb but once I'm driving it will start to climb , if I open the hot air on full it will drop down some? Any ideas lads
It's a 300 tdi 97

Normal for a diesel so remove the viscous fan, there are a few threads on the subject already.

It's not normal at all. It indicates a problem in the cooling system.

I suspect that the thermostat is staying open all the time, or has been removed. As a result your engine is being over-cooled, which is not a good thing.

Drain coolant, remove old 'stat and install new one. Then re-fill coolant circuit initially via the radiator top plug, then via the header tank and finally via the 'stat housing.

Allow the engine to tickover for perhaps 20mins to bleed, then re-check the level in the header tank.

Now check the temperature of the top hose and, with the viscous fan removed, check across the whole surface of the rad. to ensure the coolant is passing right through.

On TDi engines it is very common to run them without the viscous fan, particularly in winter. Just leave it in the boot of the car - just in cases.

A properly running Disco TDi should be a very warm place to be during winter, if it's not it needs looking into.

Dave

The thing is the blowers kick out lovely hot air once warm even with the needle on the gauge reading low

Had I think about it and if I'm honest I don't even know what I viscous fan is let alone how to remove it , anybody near cambridge want to get there hands dirty?

Got a new thermostat , going to replace that today and see what happens

Popped a new one in but not seem to make a difference , should the viscous fan be spinning on first start up from cold? Mine is

Bigman685 said:

Popped a new one in but not seem to make a difference , should the viscous fan be spinning on first start up from cold? Mine is

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Well u did say your heater was blowing hot so nothing wrong with the engine/coolant tempreture is there.

With a cold viscous coupling it will be semi locked until the viscous fluid circulates within the coupling, u shouldn't be able to 'spin' the fan by hand but only move it by the distance of one blade at a time, with the engine running u may hear the sound of the fan change after around 30 seconds, but that may depend on how noisy your engine is in the first place.

With V8 is sounds like a turbine but then disappears 100 yards down the road but will return when the viscous fluid thickens ie. with a hot engine, hot engine bay on a hot day.
As stated the Tdi is a cool running engine, designed so in theory it can be left running all day if required with a working vehicle.

Bigman685 said:

Popped a new one in but not seem to make a difference , should the viscous fan be spinning on first start up from cold? Mine is

Click to expand...

I assume its the correct stat?
I was supplied the wrong one by a local motor factor
thermostat - Australian Land Rover Owners

I find it hard to tell if the fan is working correctly or not, I would love to remove it and fit an electric one but just haven't the funds

Well after the new thermostat the heaters are defo getting hotter and the temp needle does seem to sit alittle higher, Iv now removed the viscous fan and ran it about abit today all seems very well hot warm blowing nicely and temp looks good , I'll see in the Morning if it warms up any quicker,
Had to borrow the misses car earlier to nip to b an q for a 1/2 bsp radiator bung as I managed to snap the plastic one on the thermostat housing much better with brass, thought about fitting one with a bleed valve?

Bigman685 said:

Well after the new thermostat the heaters are defo getting hotter and the temp needle does seem to sit alittle higher, Iv now removed the viscous fan and ran it about abit today all seems very well hot warm blowing nicely and temp looks good , I'll see in the Morning if it warms up any quicker,
Had to borrow the misses car earlier to nip to b an q for a 1/2 bsp radiator bung as I managed to snap the plastic one on the thermostat housing much better with brass, thought about fitting one with a bleed valve?

Click to expand...

Why not, saves taking the whole nut off

But then the 300 series is self venting via the valves in the coolant reservoir cap.

Yes would help if you replace the coolent

Mine runs cool with the temp needle near the bottom... Heaters blow out nice and hot so im gonna leave it as it is... Would rather it run cool instead of overheating

Good and bad, engine has a temp band it needs to run in, either side isn't good for it

winchman said:

I find it hard to tell if the fan is working correctly or not, I would love to remove it and fit an electric one but just haven't the funds

Click to expand...

My Viscous fan was removed the day I bought mine. Haven't put it back on since.

Runs all day long at pay and plays at the normal temp with no leccy fan.
Even when the engine bay is caked in mud like this.....





I will be fitting one soon as a precaution when I get round to it. Got one that came off the air con rad so will fit that via a switch.

Been out to the shops this evening and it feels a bit freer revving now without that big ole fan , fingers crossed it can stay off

that engine bay looks great

wow yes that is a very dirty engine lol

Quick update , since removing the viscous and replacing the thermostat the needle sits perfect and the engine gets to temp much quicker , the heaters also kick out some serious heat now , toasty
Thanks to all that replied with helpful advice