P38 Diesel Overheating again - Free Lager

Hi all,

Ive been trying for months to ascertain why my P38 DSE overheats when under load.

Symptom:
Climbing slight hills (especially with boat & trailer) causes the engine to overheat. ie: the guage continues climbing until light comes on.
If I drop a gear or 2, it slows the rate that the temp increases, but as soon as I hit the crest of the hill, and start going down or straight and level the temp returns to normal within a minute or 2.
Temp's are normal if unloaded and driving around town or on highway with no load.

What Ive done

• Replaced radiator
• Replaced water pump
• Replaced thermostat
• Replaced Viscous fan
• Replaced hoses
• Replaced water temp sensor
• Replaced radiator expansion cap
• Bled radiator properly (the car has run 1000 miles since refill)
• Replaced head gasket (head reconditioned and not cracked)
• Reconditioned turbo

Range Rover

• 1996 DSE
• Jeremy Fearn Chip and intercooler
• 110,000 miles

Help

So I am at a loss as to what is causing the overheating.
I really need help from you guys. I bought the car when I was in the UK and exported it to Australia. They never improrted the diesel here, so no Landrover mechanic has any idea about it.

Im thinking maybe the Viscous fan is the culprit. Even though it is new, it doesnt seem to operate correctly. For example, when I start the car up and drive off, there is a roar from the fan, but after 30 secs it stops. I got a rolled up newspaper and I can stop the fan very easily.
When the car gets hot the fan is still easy to stop with the newspaper. Is that normal?


Free Lager
Im really needing help from you guys.
Who ever can correctly and remotely diagnose the cause, I will sent a case of beer. Promise.

Please help. Any questions ask.

Thanks Karl
ps: Its not my fault if we beat you in the ashes.

If you fan stops that easily, I would think it is not doing the job. Otherwise an easy mod, buy yourself a Kenlowe external thermostat (about £18) and a relay and connect it to the condensor fans.( remove the existing connections to the fans) Set the stat to 85 degrees and I reckon that will cure the problem. you can cheapskate it with just a relay and switch if you want. If it does cure the problem, then I would say you viscous fan is NBG. You could then replace the viscous fan with a big Kenlowe which I'm sure would sort it and save you juice into the bargain.

I reckon the cooling system is marginal at best. with both the the hoses going to the top of the rad, it defies the laws of thermo dynamics!

Agree with Datatek, sounds like the viscous fan coupling is at fault. When hot the fan coupling should be almost locked solid and should shread the rolled up news paper with ease.

It does sound like viscous coupling is not operating right, but thinking on your comments about the angle the car is at when you have particularly high temps it sounds like you might still have some air in the system too, that moves about depending on the angle causing an air lock on the upward slopes, but shifting somewhere 'safe' on the level or downhill.

Datatek said:

If you fan stops that easily, I would think it is not doing the job. Otherwise an easy mod, buy yourself a Kenlowe external thermostat (about £18) and a relay and connect it to the condensor fans.( remove the existing connections to the fans)

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Ive actually jumpered the condensor fans so that they were permanent on, and tried it out. The bloody car still overheats.

By the way, KARLZ = KZROCKY (thats me)

I forgot I had 2 logins somehow and accidently posted it under karlz.
Same person though.

Karlz said:

Ive actually jumpered the condensor fans so that they were permanent on, and tried it out. The bloody car still overheats.

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Have you checked that the aircon condensor is not blocked with all those bloody flies you get down under

Datatek said:

Have you checked that the aircon condensor is not blocked with all those bloody flies you get down under

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No flies on me mate.
or the condensor.

Its winter in Melbourne at the moment, its cold. Was 20 today, heater on full blast.

kzrocky said:

No flies on me mate.
or the condensor.

Its winter in Melbourne at the moment, its cold. Was 20 today, heater on full blast.

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It was 18 in Melbourne at Christmas last time I visited, what do they say, all 4 seasons in a day or something like that?

If it doesn't stay cool with the electric fans going I'm surprised. The temperature rises on mine up steep hills towing the caravan but nothing dangerous. All my 4 X 4's have done that with the van.

The fact that it's better if you drop a gear making the engine work less hard but rev more still points to it being the viscous coupling for the fan. Mine would cut your arm off when it's hot and revved never mind a newspaper

Karlz said:

Ive actually jumpered the condensor fans so that they were permanent on, and tried it out. The bloody car still overheats.

Click to expand...

That could still point to a temporary airlock somewhere forming on inclines, stopping the coolant flow; thus it doesn't matter how much air you force through the rad the water in the block will still overheat, (but the water in the rad will be nice and chilled) My guess :scratching_chin: is that the bubble forms somewhere around the top of the inlet/outlet ports on the rad, these being about the highest point on an incline. This could also explain why it cools so quickly once you level out as the block gets a burst of well chilled water from the rad.

Are you sure its actually overheating?
When I go uphill or kick down, my temp guage shoots up. I simply give the rear wiper a flick and once the wipe is complete, the guage returns to normal !!!
Am fitting a new BECM next week to see if this cures this (and all the other electrical faults).
Oh, I have a '97 2.5 DSE with a tuning box and no back boxes!!!

Hi, p38 diesel owners. My 2001 temp guage sits on half way untill i am in a traffic jam in 30c as we have had this summer,then it was rising to 2 o'clock and was getting a bit high for comfort.However it never went above the high temp white line and as soon as traffic started moving again the guage went back to 12 o'clock. Is this normal.

spidercrab said:

Hi, p38 diesel owners. My 2001 temp guage sits on half way untill i am in a traffic jam in 30c as we have had this summer,then it was rising to 2 o'clock and was getting a bit high for comfort.However it never went above the high temp white line and as soon as traffic started moving again the guage went back to 12 o'clock. Is this normal.

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In a word, no...

Temp should be rock steady at 12 o'clock position.

Check your viscous fan for operation, check the rad gets hot all over and possibly the water pump - impellors have been known to work loose.

Viscous Fan is more often than not the prime cause!

Check all the new parts fan,rad,stat,pump ect..
even new parts can be faulty especially if there britpart

I really need help from you guys. I bought the car when I was in the UK and exported it to Australia. They never improrted the diesel here, so no Landrover mechanic has any idea about it.

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surly they have the 325d bmw? The early ones had the same engine so maybe try a general mecanic

spidercrab said:

Hi, p38 diesel owners. My 2001 temp guage sits on half way untill i am in a traffic jam in 30c as we have had this summer,then it was rising to 2 o'clock and was getting a bit high for comfort.However it never went above the high temp white line and as soon as traffic started moving again the guage went back to 12 o'clock. Is this normal.

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As Saint said, almost certainly the viscous fan, I can give you a mod to use the aircon fans for cooling as long as the rest of the cooling system is OK.

Check your condensor intercooler and oil cooler isn't blocked with crud!

As Dan2082 said, Are you sure it’s overheating?. When you next get into an “overheating situation”, stop the vehicle and measure the block or cylinder head temperature (the coolant temp will be within ~2C of the metal temperature. If you don’t have one buy a $10 infrared thermometer. Above 120C is overheating and 129C is boiling point.!
For info there was a bulletin that came out for pre 97MY P38s for over reading temperature gauges. At 97MY, the temperature gauge calibration was changed, the coolant sensor calibration was changed and a ground wire was added to the sensor. The ground wire was added because the temperature gauge would go up when electrical loads were switched on. This was caused by a ground shift on the engine due to a corrosion of the ground lead connections (at engine, chassis & body points). So when you go up the hill next time with a hot engine switch on the electrical screens and lamps and see if the gauge goes up. If it does this indicates a poor ground on the engine.

The viscous fan is knackered. Change it.

Check your rad. There are Chinese copies doing the rounds that don't have a baffle in them. Island 4x4 said they've seen loads without baffles. I had one (not from them) fitted and it didn't have a baffle. Simple test with a £12 usb endoscope or take the rad out and do the marble test.

I have videos if you want to see the problem.

Apologies if you've already checked...

Nik

P.S. If I was right, how do I claim my free lager?