We changed our manual Discovery 300 TDi (when it simply couldn't be welded any more) to a 2001 Rangey (2.5 DHSE) which we have been very pleased with. We own a vintage boat which we slip & recover twice a year & today was the first time that we had used her to tow our boat (boat & trailer weigh around 2.2t) No problems with pulling capacity, however we had to stop twice on the 25 mile journey home (for around 20 mins each time) due to the engine temp going into the red. This happened once on the flat & once on a hill. Any attempt to travel more than 30 mph or over 2000 revs resulted in the engine overheating.

We have looked at some of the suggestions on here but one we wanted to run past the forum members was the suggestion from a work colleague (who is an ex LR mechanic) that we should have put the air con on whilst towing (& indeed generally run with the climate control on throughout the year towing or not) as this would have prevented the overheat.

Does this make sense or have any credibility? We may well replace the components suggested in other threads but would be interested to hear your comments. I might add, that the truck normally drives perfectly (& still does after the trailering incident), we have no leaks, the viscous fan appears to work fine & at the risk of sounding obvious, there was plenty of coolant.

Any suggestions welcome, as apart from general social & domestic driving, we did buy the Rangey to tow the boat & were reassured by fellow Rangey owners that even the diesel variant would be man enough to do the job & the fact that they were also automatic would not be an issue.

Many thanks

PS - we live in flat Lincolnshire!!

cooling system isnt in perfect condition then ,does rad get hot all over ,does viscous fan lock up when hot

:welcome:your friend sounds like a true l/r mechanic...anyway id just look through the grill & check you havnt got a dead animal or 3 years of leaves clogging up your aircon/radiator first then as jamesmartins post above suggests

Water pump impellers have been known to work loose.

Air Con on will only add to the heat in the engine bay due the Condenser shedding excessive cabin temp.

Air Con Fans will come on to cool condenser - but they also come on due to extreme coolant temp too...

You have a cooling system fault.

My DSE towed faultlessly up hills and down dales all day long....

I suggest you take a look as suggested at the pump, fan and rad - the rad is top flow and as such the bottom gets silted up quickly and easily.

+1 to all above. there are 3 fans, one viscous driven to cool the engine and two electric to increase airflow when the AC is on because of the extra heat load of the AC condenser. In your friend's mind he was thinking it would be a good idea to have all 3 fans running but he didn't consider that the AC will be putting out its own heat (and quite a lot of it). Fortunately LR thought about it too and so when the engine control system thinks the radiator fan is not managing on its own it can send a request to the AC system to turn on the two electric fans WITHOUT turning on the AC.

In your case you may have (in increasing levels of hair-tearing):

1. Low coolant, just needs a top up but heyyy why not a flush.
2. Radiator fins gummed up with dirt and debris (as mentioned above). Garden hose / pressure washer / spot of steam will do the job.
3. That low coolant was due to an ill fitted or ill fitting expansion tank cap which by not allowing the system to pressurise is letting all the coolant boil away.
4. A trapped air bubble. If it was in your arteries it would be called an embolism. System must be bled but heyyy why not a flush.
5. That low coolant was due to a slow leak. Find and fix. Look for greenish stains where coolant has seeped and evaporated leaving a residue. Do also look under the car, there are little tin caps (just like on polish tins and custard), about 6 I think (not sure), along the bottom of the engine. They are designed to pop out if system drastically overheats / over pressurises. I assure you they will all still be there but you may spot seepage.
6. Viscous clutch on radiator fan is weakening. Search this forum for newspaper test. Replace viscous fan OR get in touch with Datatek and he'll show you a trick to get the two electric fans to run all the time.
7. Electric fans aren't coming on at all. Need to troubleshoot with an electrician and you will need diagnostics. Actually you may tear more hair out with this than with the next which will only give you skinned knuckles.
8. Radiator is toast. Check (carefully) for hot and cold spots indicating blocked arteries. If nothing, take it out, drain and weigh. A good one weighs just under 5kg I reckon. But they do silt up so if it weighs significantly more its time to replace.
9. Water pump is toast. No way to know without opening the engine front casing and taking a look.
10. Engine block is cracked. Hot gasses are getting directly into the coolant and overpressurising the system. The most sensible solution at this point requires an empty field, litre of petrol and a box of matches.

It may seem overwhelming but a systematic approach will see you past almost anything the P38 will ever throw at you. Good luck!

Having aircon on would cause overheat quicker as it is loading the engine. Maybe that's why he is an EX land rover mechanic.

Might be a stupid suggestion but, having towed a lot with my Rangie, 4 wheel trailer plus car, the one time it behaved like that was when the brakes binded on one of the trailer wheels. Never the most powerful Lugger but adequate once the brake was fixed.

lets assume your trailer is fine.
Maybe confirm your head is fine also.
then you have a cooling system fault.
good RR stat (checked before you fit)
water pump with metal impeller
radiator with Baffle in top. (checked before you fit)
do data mod for ease and your done.
£500 DIY
Make sure you have hi mix of antifreeze.

..

I to went from a Rangie auto with the 300 TDI, which pulled a 1900kg caravan without any major effort. We changed to a P38 and (although we never suffered any overheating issues) found I needed to keep pushing it to get a reasonable 56 mph when towing. It always appeared to be underpowered.

I now tow with an L322, and no problems except one, I stuggle to keep the speed off

Alan

donp38 said:

lets assume your trailer is fine.
Maybe confirm your head is fine also...

..

Click to expand...

Well we know his head ain't fine or he would't have bought a Rangie!

acc said:

i to went from a rangie auto with the 300 tdi, which pulled a 1900kg caravan without any major effort. We changed to a p38 and (although we never suffered any overheating issues) found i needed to keep pushing it to get a reasonable 56 mph when towing. It always appeared to be underpowered.

I now tow with an l322, and no problems except one, i stuggle to keep the speed off:d

alan

Click to expand...

+1

wammers said:

Having aircon on would cause overheat quicker as it is loading the engine. Maybe that's why he is an EX land rover mechanic.

Click to expand...

Actually Tony that is not always so, if the viscous is shot putting the aircon on will most likely bring on the aircon fans which will bring the temperature under control in most cases on the diesel.

rasheed said:

+1 to all above. there are 3 fans, one viscous driven to cool the engine and two electric to increase airflow when the AC is on because of the extra heat load of the AC condenser. In your friend's mind he was thinking it would be a good idea to have all 3 fans running but he didn't consider that the AC will be putting out its own heat (and quite a lot of it). Fortunately LR thought about it too and so when the engine control system thinks the radiator fan is not managing on its own it can send a request to the AC system to turn on the two electric fans WITHOUT turning on the AC.

Not on the diesel

In your case you may have (in increasing levels of hair-tearing):

1. Low coolant, just needs a top up but heyyy why not a flush.
2. Radiator fins gummed up with dirt and debris (as mentioned above). Garden hose / pressure washer / spot of steam will do the job.
3. That low coolant was due to an ill fitted or ill fitting expansion tank cap which by not allowing the system to pressurise is letting all the coolant boil away.
4. A trapped air bubble. If it was in your arteries it would be called an embolism. System must be bled but heyyy why not a flush.
5. That low coolant was due to a slow leak. Find and fix. Look for greenish stains where coolant has seeped and evaporated leaving a residue. Do also look under the car, there are little tin caps (just like on polish tins and custard), about 6 I think (not sure), along the bottom of the engine. They are designed to pop out if system drastically overheats / over pressurises. I assure you they will all still be there but you may spot seepage.
6. Viscous clutch on radiator fan is weakening. Search this forum for newspaper test. Replace viscous fan OR get in touch with Datatek and he'll show you a trick to get the two electric fans to run all the time.
7. Electric fans aren't coming on at all. Need to troubleshoot with an electrician and you will need diagnostics. Actually you may tear more hair out with this than with the next which will only give you skinned knuckles.
8. Radiator is toast. Check (carefully) for hot and cold spots indicating blocked arteries. If nothing, take it out, drain and weigh. A good one weighs just under 5kg I reckon. But they do silt up so if it weighs significantly more its time to replace.
9. Water pump is toast. No way to know without opening the engine front casing and taking a look.
10. Engine block is cracked. Hot gasses are getting directly into the coolant and overpressurising the system. The most sensible solution at this point requires an empty field, litre of petrol and a box of matches.

It may seem overwhelming but a systematic approach will see you past almost anything the P38 will ever throw at you. Good luck!

Click to expand...

On early diesels there is no call to the aircon fans for an overheat, on late models there is a third sensor in the head that does bring the aircon fans on but only when overheating has already occured.
As others have said check the viscous fan, most likely from the description, then water pump, & RAD.
May also be worth fitting my aircon fans mod.

Datatek said:

Actually Tony that is not always so, if the viscous is shot putting the aircon on will most likely bring on the aircon fans which will bring the temperature under control in most cases on the diesel.

Click to expand...

Maybe i should have said if all is normal. Aircon loads the engine that is why the V8 and the later diesels have a temp sensor to put the aircon fans on in the case of an overheat even if the refrigerant is does not need cooling. Opening the windows and setting heater to high would certainly help engine cooling but not the aircon.

Wammers is correct about putting the heater on to help cool down, except if your matrix o rings are on the way out and allowing air into the system an airlock could be exacerbating the problem and the resultant depressurisation of the cooling system will allow the coolant to boil at a lower temperature.
I had o ring issues on mine (easily spotted with damp drivers footwell) and caught the rise in engine temperature whilst towing before it got too hot, now the o rings are done I've had no further temperature issues....

BOOMER said:

Wammers is correct about putting the heater on to help cool down, except if your matrix o rings are on the way out and allowing air into the system an airlock could be exacerbating the problem and the resultant depressurisation of the cooling system will allow the coolant to boil at a lower temperature.
I had o ring issues on mine (easily spotted with damp drivers footwell) and caught the rise in engine temperature whilst towing before it got too hot, now the o rings are done I've had no further temperature issues....

Click to expand...

You obviously missed the "If all is normal bit."

wammers said:

You obviously missed the "If all is normal bit."

Click to expand...

I don't do normal, nothing is normal in my life!

BOOMER said:

I don't do normal, nothing is normal in my life!

Click to expand...

Of course it isn't with a P38 in it XD

TCubed said:

Of course it isn't with a P38 in it XD

Click to expand...

Correct!! :doh:

acc said:

I to went from a Rangie auto with the 300 TDI, which pulled a 1900kg caravan without any major effort. We changed to a P38 and (although we never suffered any overheating issues) found I needed to keep pushing it to get a reasonable 56 mph when towing. It always appeared to be underpowered.

I now tow with an L322, and no problems except one, I stuggle to keep the speed off

Alan

Click to expand...

Is the L322 diesel a lot more powerful? As I've driven a couple of P38 diesels and found them a bit sluggish. Probably going to get an L322 next year and can't decide between diesel vs petrol!