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1995-2002 Range Rover P38A
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Discussion Starter · #1 ·
Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated !

OK – help much appreciated on this one as it is frying my noodle ! – I’ve waffled on to give as much insight as I can.

She is a 1999 THOR engined 4.6 HSE P38; my pride and joy and almost concourse (man am I spending time and polish, and using daily, well was).

Maintained manically – oil every 3k etc, coolant / all fluids every year etc had new air con rad and dryer a year ago, always runs spot on, 22mpg (yes really! – well ok not in town!) Air con always set to 18 and whispers away; Never gets hot, temp gauge sits just left of vertical whatever the temp outside. Genuine thermostat and pattern water pump about a year ago.

Only tiny fault is a drip (maybe an egg cup a month) from a block under the throttle housing with pipes going into it – no idea what it does but have left well alone as all I need do is clean the left hand rocker box / manifold every month.

So – the problem: two weeks ago I managed to get two guys running for cover as “smoke” started to billow, well ok waft out of the vents under the windscreen – on inspection it looked like maybe the small drip had become a squirt and evaporated on the manifold cover; Note also that the HEVAC unit displayed the dreaded book sign and the air con compressor stopped working. Drove home (temp ok) & did the heinous crime of adding radweld – problem sorted, run her for a week, long journeys no problem at all, apart from HEVAC sign once or twice after air con compressor had stopped – turn off, re-start – all good.

Then a week ago to the day, after a 30 minute average drive the compressor stopped running, 2 minutes later the HEVAC sign came up, another two minutes and the temp gauge shot, literally into the red (took 45 seconds max) – red temp lights up. Pulled over. Swore. Wife took dog out of the car, muttered something and wandered off.

Engine didn’t smell hot at all – but the expansion tank was full to the brim.

Waited for recovery, got bored after two hours, started her – all fine, temp cold, drove to the pub J

Driving back the same scenario – air con cuts out, HEVAC sign, Temp rises. Turn off, wait 5 minutes, turn on – drive ten minutes, repeat.

SO – RR tec reads codes, finds the temp sensor connected to a pipe in the cabin (I guess to the heater matrix) has fallen off (bracket broke) – re-attaches, runs the car up to temp, no fault codes at all, idles for 45 mins – all good. (Nice to see tell tale holes cut away once the paneling is off so assume the blend motors have been fixed! Every cloud…)

I drive out to the pub (I know, re-ocurring theme here) – 25 minutes out; air con compressor cuts out NO HEVAC sign, 2 mins later the temp shoots to red, light comes on. I drive on (5 mins or so), park up, lift the bonnet and a) expansion tank totally full again and b) very strong smell of burning, almost an electrical smell – but assume cooked engine, oh dear…

Two hours later – engine still smells, but starts, no problem, gets us almost home before the same scenario – air con compressor cuts out; NO HEVAC error, temp gauge dances around like a weird thing before going to red.

RR Tech reads codes – not a thing; Checks for mis-fires – not one; no oil in water or water in oil; no expansion of coolant pipes until they are hot. Suggests thermostat as the bottom hose from rad to stat is warm, never hot ? Should it be I wonder ?

SO – new genuine thermostat from RR, re-filled, air locks out – drive for 30 minutes, all great ! yea ha…. And then, air con compressor cuts out, temp gauge dances around like it’s at a rave, so I floor her (well, why not) and the gauge drops… - then climbs a little, then hits red so I turn the heating to max and it drops down again – drive home (5 mins), turn on auto a/c again and set to 18 – compressor works, all is good then just as I reach home temp soars again.

In summary – IF I hadn’t had the smelly engine I would doubt she is overheating at all; It’s odd she goes from normal to red light in around 45 seconds, and can be fine within 3 minutes of shutting down and re-starting, sometimes yet others you have to wait maybe 15 minutes; if you put water in the top of the rad it comes out the bottom hose fine;

Last random note – this weekend I gave up, as she had developed a really loud tappit noise on one bank, so I assumed the worse; parked her up and left alone. Then today I had to move her – note, coolant level perfect at cold, not lost a drop, oil clean as clean, start her up – no tappit noise at all! – dunno about overheating as too worried to take her out; RR tech 100% positive we can’t have a head problem as she runs and idles just too well. Second Random note, in the two weeks this has been going on she has idled 200 rpm above normal (rock steady at 750 normally) – may be coincidence but I mention it all the same.

Well – has any one made it to the end ! ? if you have, and if you can help I am happy to re-imburse, thank lots, lend my wife out as the RR really is my pride and joy – plus took me 4 years to save for, so I’d really like to save her…
 

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1995-2002 Range Rover P38A
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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Hi. As I have a Diesel, I don't know the setup on the petrol engines, i'm sure someone who does will comment though. I'm just wondering, with so many different symptoms, could your belts have come loose or have oil on them? This would explain the burning smell, low oil pressure, no cooling and the aircon causing the book symbol to appear as it may be providing a very limited drive. I know on the diesel I would have a power steering loss and no charge warning as well but as I say, i'm poor and have a diesel :) I'm aware slack belts are usually signalled my a squeal when they slip but I have a personal experience where it didn't make a sound but was slack enough that it couldn't turn some of the more difficult pullies properly but did manage to drive the alternator due to the way the belt was routed.

Otherwise - not got a clue.
 

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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Might be worth checking your a/c clutch and compressor. Sounds like one or the other could be locking up, this would certainly lead to the burning smell as the belt is then dragged over the now stationary pulley, have a look on the underside of the belt for signs of burning or melting.
 

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1995-2002 Range Rover P38A
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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Hi

The aircon cut out can be caused by the engine ecu when it detects that the engine has to work too hard. An other possible cause from the AC cut out is the tri-pressure switch when the pressure gets too high (not enough cooling of the gas in the condensor) or too low (not enough gas in the system).

As for the sympthoms of the engine overheating. Check the dearating pipe from the radiator towards the expansion tank. The expansion tank has a small hole and pipe inside and water should come out of the small hole when the engine rpm is up to 2000 rpm. If the pipe is clogged you might have airlocks in your cooling system that can cause hot spots and disturb the cooling water flow. The sudden shooting up of the temperature could be coolant that has not been circulating enough to pass the sensor. Radweld is known to seal the dearating passage. Air trapped in the system expands and pushes liquid into the expansion tank when the system gets hot explaining the level rise in the expansion tank. You have to run the engine from cold with an open dearating pipe until it becomes hot and keep on filling the coolant when the level goes down until you get a steady stream of liquid in the expansion tank.

This is a short movie of my expansion tank and the liquid that is squirting out of the small hole. The bulk of the liquid escapes through the pipe that is normally submerged.In my expansion tank I have incorporated a level sensor that warns me when the fluid level has gone down.



Regards

Jos
 

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JACK'S GRANDAD
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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

I would be checking all the pulleys that the belt runs across myself.
May well be electrical, but by popping the belt off and checking the pulleys by hand, it would at least rule them out.

Martin
 

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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Wild guess - fuse box.


certainly worth checking.
 

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Discussion Starter · #7 ·
Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Hi All - many thanks for all the help; will go check out every suggestion. The small pipe that returns to the expansion tank btw is free flowing when the thermostat is closed but dribbles at best when open - any one know if that is normal? ask the bottom hose from rad to thermostat, it never gets hot at all, is that normal too?

I'll get there in the end ! - thanks again!
 

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Discussion Starter · #8 ·
Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Hi All - Update :) - ok so narrowing everything down the clever money is now that I do indeed have a flow issue (well, I am middle aged); The engine really is overheating, if you turn the cabin temp up to max it drops down, also at speed the problem is less acute (more air flow). The air con compressor is indeed cutting out as the management system is reading a hot engine but, thankfully only coolant - the motor cools way to fast for a real overheat / head warp panic.

The final clue was the bottom hose never getting hot, we think that the rad is blocked - partially, and or moving an airlock around which makes sense as hot water hits the temp gauge and the temp then registers hot...

New Rad on its way tomorrow, new thermostat already on, water pump a year old and clearly working, return pipe clear and working; I'm going to flush the whole system with rad flush, then water, the re-fill and then assuming the bottom hose gets hot I'll test for exhaust gasses using a bloke leak combustion gas tester - assuming that checks out ok I'll road test and let you all know.

Odd though - the rad looked quite new, and water does eventually make it from top to bottom, but not very quickly !
 

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1995-2002 Range Rover P38A
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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

OP, sounds very much as if Radweld has claimed yet another radiator! BTW the small throttle body heater you referred to quite often leaks. Common to a number of things on the P38, it isn't a great design. There are kits avaliable on eBay and such like to cure this annoying problem. However, the throttle body heater is only needed in severe cold climates - not as severe as you will see in Hertfordshire so you can get away with just connecting the hoses together with a 'U' of copper pipe or similar and bypass the leaking heater unit with no ill effects.
 

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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

As most of the P38 lovers, I also bypassed the throttle body heater and got rid of that tiny but annoying water loss, advise you the same while you are changing the radiator, of course if you are not living in a cold country.
 

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Discussion Starter · #11 ·
Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

Hi All - many thanks for the throttle advice - will certainly bypass that :) - so the update, old rad had limited flow (determined by blowing through it and comparing to the new one !); new rad on, flushed, and guess what - now no water via the return pipe, top hose doesn't pressure up even when temp gauge is at normal, bottom of the rad is cold, top is hot; I'm thinking now the water pump I fitted a year ago (pattern) maybe, as there seems to be no real flow.. so watch this space, new water pump on it's way Friday - I guess at this rate she will be like that only fools and horses broom sketch "I've had the same broom for 14 years. Had ten heads and five handles".
 

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Discussion Starter · #12 ·
Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

The Latest ! - so swapped out the Rad for a new one, new thermostat (genuine), new water pump (quality OEM job), to be honest the water pump looked fine... test driven for an hour now and the temp guage stays just left of centre, car runs better than ever, it's warm (for once!) today at 21 C and the climate control is whispering away at 18 perfectly.... we will take her out on some runs tomorrow and report back, still not sure of the route cause, will investigate the old rad tomorrow..
 

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Re: Really interesting ? P38 Overheating (or not) Mystery - all help much appreciated

DougsP38,
Great post, thanks andI hope the problem on your car is now fixed as I have a Gems 4ltr P38 with the same "mystery" sudden overheat.
Before I read your post I had assumed I had a faulty Viscus fan fitting having changed the water pump last October after it started to squeal!
I changed the viscus unit last week and the "problem" had gone, until today when the gauge zoomed over to the red !
A cool lower hose is a symptom of a stuck thermostat according to the fault finder in the workshop manual BTW.
Looks like I need a new rad and it will be worth changing the stat as well.
Here's hoping!
 
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