P38 2.5DT running cool

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bbjunkie

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Just picked up our first 2.5DT Range Rover (P38) and while driving I have noticed the temperature gauge never gets above the top of the blue section, in actual fact at one stage yesterday it went down from the top of the blue section to about halfway up the blue section.

At first I was worried about a possible head gasket problem, however after getting out and checking the hoses there was no excess pressure, the coolant in the header tank was warm (not hot) to the touch. When I squeezed both hoses together the level in the header tank went up and down, so I assume the thermostat was open (or is it possibly missing?) Today while climbing a large hill the gauge went up to around the middle of the white section, but soon dropped to the top of the blue section again when over the crest.

(The cabin heater is working without fault)

Is this normal?

Cheers
Pete
 
I would say, yes, its normalish - my diesel P38 has always run just above the blue section, just into the white area. It actively moves depending on the load on the engine, so climbing a long hill will get the temp up as will a warm day when the A/C is on. Never past the 12 position on the gauge though.

If its staying right right down in the blue section then you could have a bit of a stuck thermostat possibly but I wouldn't be too worried about it. I would be more worried if it was rock solid at 12 the entire time and possibly creeping past the 12 mark.

You dont have the fan roaring away though do you as though its working hard to cool the engine??

-Wills :)
 
I don't think so, not noticed it anyway. Apart from the once when climbing the hill, it usually sits at the top of the blue - not into the white at all.

I'll read the service manual and see about checking the thermostat 1st I think.

Pete
 
Getting the stat out isnt too much of a bad job, once its out get a bowl of boiling water and put it in, check it opens ok, then put it in a bowl of cold water and see what happens, you should get your answer as to whether you have a buggered stat :)

-Wills :)
 
Good idea!

Something which I've been wondering about, since reading the service manual is, what are the chances it's the viscous fan unit that's overcooling the radiator?

I suppose, check cheap things first - right?

If it does happen to be the viscous fan unit, anyone know somewhere I can get the specialised tools cheap to replace it?
 
bbjunkie said:
Good idea!

Something which I've been wondering about, since reading the service manual is, what are the chances it's the viscous fan unit that's overcooling the radiator?

I suppose, check cheap things first - right?

If it does happen to be the viscous fan unit, anyone know somewhere I can get the specialised tools cheap to replace it?
Click to expand...
hi,scrap the viscous fan and stick a kenlowe fan kit on it,much better and will not use as much fuel.
 
I had the same issue, the gauge was always in the blue section, so I replaced the thermostat and now it sits nicely at 12 o'clock.

Incidently I tested the old thermostat in boiling water and it opened as it should, but for some reason it couldn't have been doing that when in the engine.

Your viscous fan should roar when you start up the engine, but then become silent when you drive off. You can test it by sticking a broom handle in the fan when the engine is cold and it should stop it. Of course if the viscous unit is siezed you will either break the fan and/or the broom handle, so its something I've never tried myself!

On warm days the fan roars when in slow moving traffic, then goes silent after doing its job, just as it should do.
 
gemsdad said:
hi,scrap the viscous fan and stick a kenlowe fan kit on it,much better and will not use as much fuel.
Click to expand...

...but why would you want to do that when the viscous fan is fine and perfectly capable of doing the job it was meant for. The whole 'it will use less fuel' thing is just silly, it may use a tiny bit less fuel but hardly that much. An electrical load is still needed to power the fan which still uses fuel. Stick with the viscous fan.

-Wills :)
 
hello!

a question looking to but a 2.5 dt range rover, do you recommend it. currently looking at one but a problem runs fine when driving but in traffic slow driving heat temp slowly rises and heater goes cold? any ideas rad, water pump replaced
 
wills said:
...but why would you want to do that when the viscous fan is fine and perfectly capable of doing the job it was meant for. The whole 'it will use less fuel' thing is just silly, it may use a tiny bit less fuel but hardly that much. An electrical load is still needed to power the fan which still uses fuel. Stick with the viscous fan.

-Wills :)
Click to expand...

Removing the viscous gives a faster warmup because the viscous fan runs whether needed or not. True it provides lees cooling when cold but it is still forcing cold air through the rad and over the engine. This weather, electric fans rarely run which is why the warm up is quicker. My last 4 X 4 with an electric fan turned in an improvement of 3mpg in winter and 1 to 2 in Summer. A quicker warmup will also prolong the life of the engine.

I plan to get rid of the noisy viscous fan on my DHSE A.S.A.P. I don't plan to buy an expensive Kenlowe though as there are already 2 electric fans for the aircon condensor that rarely operate in our cool climate. It's a simple cheap mod to activate these fans from water temperature as well as aircon pressure. It is a system that worked fine on my last 4 X 4:D
 
Hi, i have recently had to replace the cylinder head on my 2.5DT 1997 R Reg due to it developing a crack in the no1 cylinder exhaust port. I have replaced the head with success but as a result it seems that the temperature gauge has stopped working. It has the same sensors in it as the previous head as i swapped them before rebuilding the engine. I have run it standing for 30-40mins and both of the top rad hoses have heated up but still nothing on the gauge. When i put the ignition on the needle does move to just under the white line before the blue part but no further than that even when the engine seems hot. Do i just need to take it on a longer run or does anyone else have any ideas why this might be happening ?
 
veedubmad said:
Hi, i have recently had to replace the cylinder head on my 2.5DT 1997 R Reg due to it developing a crack in the no1 cylinder exhaust port. I have replaced the head with success but as a result it seems that the temperature gauge has stopped working. It has the same sensors in it as the previous head as i swapped them before rebuilding the engine. I have run it standing for 30-40mins and both of the top rad hoses have heated up but still nothing on the gauge. When i put the ignition on the needle does move to just under the white line before the blue part but no further than that even when the engine seems hot. Do i just need to take it on a longer run or does anyone else have any ideas why this might be happening ?
Click to expand...

Maybe the previous owner removed the stat due to overheating problems?:eek:
 
Datatek said:
Removing the viscous gives a faster warmup because the viscous fan runs whether needed or not. True it provides lees cooling when cold but it is still forcing cold air through the rad and over the engine. This weather, electric fans rarely run which is why the warm up is quicker. My last 4 X 4 with an electric fan turned in an improvement of 3mpg in winter and 1 to 2 in Summer. A quicker warmup will also prolong the life of the engine.

I plan to get rid of the noisy viscous fan on my DHSE A.S.A.P. I don't plan to buy an expensive Kenlowe though as there are already 2 electric fans for the aircon condensor that rarely operate in our cool climate. It's a simple cheap mod to activate these fans from water temperature as well as aircon pressure. It is a system that worked fine on my last 4 X 4:D
Click to expand...

Helloooooooooo, is it easy to do? (convert fan) i thort about it a few times as im sure i thort i heard the elec fans come on a few times, must of been my ears lol, it is something id like to do tho as my viscus is knackerd, sends a vibrtion threw the car, grrrrrr :mad::mad:
 
Mike v.t.s said:
Helloooooooooo, is it easy to do? (convert fan) i thort about it a few times as im sure i thort i heard the elec fans come on a few times, must of been my ears lol, it is something id like to do tho as my viscus is knackerd, sends a vibrtion threw the car, grrrrrr :mad::mad:
Click to expand...

Very easy job, hardest bit is removing the old viscous fan and making a connection to the black/blue wire on the dual pressure switch which is easy to see but hard to get hands to:D Just need a stat, a relay, a supressor diode and a box to put the gubbins in. Total cost less than £20.
 
There was a stat in the engine before i replaced the head so whilst i had it all apart i replaced it with a new one just to be safe!

Any other ideas ?
 
Yes rad gets hot along with both hoses at the top.

Is the sensor for the gauge the one in the head nearest the radiator ?
 
Hi Pete, mine stays pretty cool to as does my mates and an Omega I had years ago also the same, towed a 23 foot boat 500 miles and never went above half way and I was pushing it aswell. I changed my viscous fan, I removed front cover, radiator hoses and side bolts, moved the rad a couple of inches forward, mole grips onto shaft as back up and a 34mm (I think) spanner onto back of fan, quick tap on spanner and off it came (remember make to break, left hand thread) shroud and fan come out together. Simple job. Hope this helps
Davie
 
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