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"Overheating" P38


geoffbeaumont

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Deerstalkers and pipes at the ready...

On the way back from work last night, stuck in traffic in the snow the temperature gauge on the P38 (diesel) went up into the red - I put the heater on full blast and it dropped back into the middle of the gauge. Couldn't see anything wrong - radiator looks okay externally, fan seems fine, coolant level is fine.

This morning it went up into the red while on a gentle throttle at 40mph in sub-zero temperatures - put the heater on full blast but there wasn't much heat coming from it... However, needle dropped so I carried on - it kept heading for the red though, and I found that regardless of road speed and load the best way to keep it low was to keep the revs up (caused me some concern when I got stuck in traffic behind an accident - low range to the rescue). Other than the temperature gauge there was no indication of anything amiss and it got me to work (20 miles of mixed driving). Struggling to think what could cause it to behave this way - maybe a failing water pump?

I decided to risk setting off home, expecting to have to drive with the gears locked down again - but the gauge rose to the middle and stolidly stayed where it belonged all the way back, even after the paranoia eased and I turned the heater down.

The only thing I can think of that could behave this erratically is a failing temperature sensor or a fault in it's wiring, but can anyone suggest any other possible causes I need to eliminate?

:huh:

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When it happened did you open the bonnet and did the engine bay appear to be hotter than usual??

Have you considered a faulty/sticking thermostat or having a radiator specialist cleaning out the radiator?

My guess is there maybe a radiator issue because when you turn the heater on which is really just another (Smaller) radiator you can get the temperature down.

I'm not sure about the P38 but in earlier models I've had experience with, the heater is basically on at all times just the flaps/doors into the vehicle are closed and the fan isn't turned on.

Good luck.

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i had a simler prob with my classic ,i put mine down to two things sticking thermo and a build up of sludge is the system.

is there any play in your water pump.

I would change all thermostats and drain then back flush the system just (use hose pipe) do rad first then do your heater matrix (use pipes at back of engine) hope this helps

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When it happened did you open the bonnet and did the engine bay appear to be hotter than usual??

I didn't get a chance - I was already late for work and it didn't overheat on the run home.

Have you considered a faulty/sticking thermostat or having a radiator specialist cleaning out the radiator?

Sticking thermostat might be this intermittent, but would high revs help? I guess maybe if it's sticking part open.

My guess is there maybe a radiator issue because when you turn the heater on which is really just another (Smaller) radiator you can get the temperature down.

I'm not sure about the P38 but in earlier models I've had experience with, the heater is basically on at all times just the flaps/doors into the vehicle are closed and the fan isn't turned on.

Except that when it first went into the red in the morning I put the heater on full blast and got hardly any heat from it, which suggests it wasn't actually that hot...

As far as I'm aware all cars circulate coolant permanently through the heat exchanger, but if you aren't diverting that heat elsewhere it will very quickly cease to have any significant cooling effect.

Think I'll change the thermostat and backflush the radiator though, if only for peace of mind!

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All the suggestions I can think of are of tthe 'can't really believe this' variety.

Lack of heat suggests no coolant in the matrix - but you say the level is fine (checked hot or cold?).

Overheating in cold weather suggests partially frozen coolant - but surely not, if the mix started out as 50/50?

Overheating while stationary / slow moving could be a very slippy fan VC, but people don't report sudden failure of these VCs, it's normally gradual.

Faulty pump impeller would always affect operation, so why the one off happening?

I can't suggest any particular remedial action.

As precautions I can only suggest you double check the coolant level while cold, confirming if possible it's anti-freeze strength.

Then it's just whatever you feel happiest doing.

If you are buying parts for a thermostat change, don't forget you might want new O rings, a large one for the housing, a smaller one for the heater pipe. From memory I don't think there is anything else.

Good Luck.

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I didn't get a chance - I was already late for work and it didn't overheat on the run home.

Sticking thermostat might be this intermittent, but would high revs help? I guess maybe if it's sticking part open.

Except that when it first went into the red in the morning I put the heater on full blast and got hardly any heat from it, which suggests it wasn't actually that hot...

As far as I'm aware all cars circulate coolant permanently through the heat exchanger, but if you aren't diverting that heat elsewhere it will very quickly cease to have any significant cooling effect.

Think I'll change the thermostat and backflush the radiator though, if only for peace of mind!

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My only experience other than radiator and thermostat was a failing engine temperature sensor which used to cause the engine to think it was still cold and supplied extra fuel to the injectors, resulting in over fueling, took some time to isolate it but when I did it was a $30AU$ part and problem was solved.

I would definitely do the cheap easy things first like the Thermostat, flush radiator as best you can, double check coolant level, check oil in sump to ensure there is no coolant loss to the sump because of head gasket/cracked head/slipped liner etc. also check no other leaks from hoses and water pump seal.

No heat from heater could also mean that the door wasn't opening or that there was lack of coolant in the system.

I hope you track it down before it becomes a money pit....Good luck, let us know how you get on.

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Coolant level was checked cold - I haven't changed the coolant since I bought the car last summer, just topped it up with neat coolant in case it wasn't strong enough, so it's possible that it's not the correct mix. However I've used it in colder temperatures than we've had this week with no problems. A coolant change certainly won't do any harm, but I'd be surprised if that was the problem.

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Well, coolant changed and new thermostat fitted, so we'll see how it goes. All flushed through and no sign of any blockages/significant crud apart from a blocked breather pipe from the radiator back to the header tank - bled it with that off as I couldn't clear it, I'll have to either replace it or get a garage to blow it through with an airline.

Only been for a short drive so far - started going up into the red and then settled down, so hopefully that was just an airlock clearing. I guess with the blocked breather it may well have been airlocks causing the problems.

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Well, we'll see how it goes turned out to be "not very well"...

Took the expansion tank cap off on tuesday before leaving work to check the level (looked empty - was actually up to the top) and there was an eruption of coolant. It had been sat for hours so this was not good... Put the cap back on and set off, without any great expectations of making it far. Sure enough, up into the red and stayed there, so I pulled over and called the AA, who told me they were very busy (I was later told I was job 12400 odd, they normally expect to hit about 8000 by midnight) but if I didn't mind a local garage they could get someone to me quicker that way. The mechanic who came out refilled and bled they system then went over it, couldn't find anything wrong other than the blocked return from the radiator to the expansion tank but told me that needs to be flowing for the system to work properly, and it had probably been partly clagged and blowing through as the pressure built up when I was having the intermittent overheating problems. The blockage was actually in the expansion tank inlet itself, not the pipe, so it couldn't be bypassed and he could only clear it as far as the bend. He had a suspended lift truck so I had to wait for the AA to send another vehicle - finally got home at ten to eleven :(

I don't run to an airline so there was no way I was going to unblock the inlet - picked up a new tank from the local dealer (it's a dealer only part) on friday and fitted it this morning. Topped up the system with neat anti-freeze, which by my calculation has roughly compensated for the plain water that went in on tuesday and bled it. Had to put the cap on and go for a drive to get it warm enough to open the thermostat, but all seems well now - survived a trip to the garden centre and a long slog back up the hill to Frankley with a heavy load in the back, and no sign that I've caused any head gasket issues :)

Just feeling a bit of an eejit for thinking I could get away with running with that pipe blocked while I waited for a new one (not that it would have fixed it) :blush:

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  • 2 weeks later...

Needless to say, it was wildly optimistic to think changing the header tank had solved all my problems... She ran flawlessly for nearly a week, then suddenly shot into the red and stayed there just before I got home on friday evening last week :( Pulled onto the drive with coolant pissing out the header tank overflow and the coolant pipes all rock hard.

Next day it was still pressurised when I took the cap off and erupted coolant everywhere. Tried to top it up/bleed it, but there was a steady stream of bubbles. I haven't got time to do anything about it at the moment, so managed to get it booked into a garage in Tyseley (was referred there by one of the local indies - it seems a lot of them won't touch the BMW engine as it requires special tooling to change the head gasket*), and the AA took it over there this friday. I'll hopefully get it back middle of next week, so I'm currently driving a hired Corsa (deeply horrible little car - I've never driven anything with more confusing controls). AA tested for exhaust gases in the coolant (positive), so heat gasket is almost certainly gone - just got to hope the head itself has survived the overheating :mellow:

* - It looks from the workshop manual that the tooling is to lock the timing while the camshaft is removed. I've found reports of people making their own and doing the job successfully, so it isn't an impossible DIY job if you have the time and experience.

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I have yet to have to do this job (change the headgasket) but I have been very strongly advised that the block holes for the head bolt should be re-threaded, and that Wurth items are a more effective design than the more commonly known Helicoils. This is taking into account that the rethreading is being done in-situ, rather than on a workbench.

The logic was that there is so much stress involved to 'bend' the head that the threads are weakened.

Obviously you have to go with what the local repairers are comfortable with. It seems risky to argue with them if they are putting a warranty on their work, but if they are sucking their teeth about the chances of long term success then advice is something to consider.

Given the work involved, deliver Friday, return by the following Wednesday seems pretty quick. They must be concentrating on it :-)

Whatever, Good Luck.

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I'm not certain when I'm getting it back - they aren't starting on it until tuesday. Whether it's done in a day will, I guess, depend a lot on the state of the head.

At least one of the local indies (the one that referred me to him) sub work on this engine to the garage it's at, which I doubt they'd do if they weren't pretty confident of good results since the fallout would mostly blow back on them. He seems to specialise mostly in engine work on the more recent Land Rover models.

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If the garage has adopted engine refurb as a specialism, especially if used by others in the trade, I'd say there is every chance their practice will be good. Up to you to decide if you ask for details as to what they are doing.

The person speaking to me HAD an engine refurb business, but was now doing a different job in the motor trade, working for someone else. I got the impression he closed his business partly due to the pressures of running his own business, and partly because he wanted a job with more variety in it.

Incidentally, the 'problems' I seemed to find with hired Vauxhalls were all around uncomfortable seats. Still other people survive them :-)

Some people ask whether driving something other than a Land Rover is confusing, but I find everything else I drive is so different that there is no risk of confusion.

Cheers.

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The seats in this one are actually pretty good - a lot better than older ones I've been in - and I've driven plenty of other cars without too much trouble, but this one took a bit more effort... The stalks are flick to operate rather than multiple position - indicators are straightforward enough, though they self cancel way to easily most of the time (and others don't cancel at all) and it's very easy to get main beam at the same time (presumably flash the lights if they aren't on). The wipers seem to work by flicking them multiple times to get different settings, but so far I'm still stumped by the rear wiper. Turned it on once, but I don't know how...

As for the stereo - took me ages to turn it on (again, still not sure how...) then couldn't turn it off until I'd pulled over and filled for a bit. Turns out you press the enormous round switch in the middle of the dash that doesn't appear to have anything to do with the stereo...

Had to cane the living daylights out of it going up Mucklows hill, too, with just me in it. Wouldn't be any fun with passengers :rolleyes: I wasn't even driving up to the speed limit.

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Not good news so far :( Cracked cylinder head, so it needs either a replacement cylinder head or engine. The garage are trying to source them and get back to me with costs, but it's going to getting into financial write off territory, so I may end up scrapping the vehicle :(

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  • 2 weeks later...

Well, I'm still Range Rover-less :rolleyes:

Found a decent engine (I hope) from a breakers and arranged to have it delivered to the garage - they couldn't deliver before easter but the garage were busy anyway, so not a big problem. Delivery day came and went, despite the garage chasing them. Couldn't provide a courier tracking number or estimated delivery time. They eventually confessed to the garage today that their courier had discovered they weren't insured adequately for the value of the engine (no, I haven't paid that much...!) and couldn't sort it out until next week. Me thinks the 'courier' is sweaty bob the local man with a rusty white van...

The garage is closed next week so it's going to be at least another week and a half before I get the car done...it's already been off the road for a month!

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Jeez your not having a good time with this one!

Another engine sounds like the best option, I did that when my one went the same way, incidently mine was caused by a very poorly done head gasket replacement, they used the original head bolts.

Lots of engines out there but unless it comes from a range rover of simillar age you will need to swap over a lot of bits icluding the injection pump.

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  • 4 weeks later...

And what turned up was...nothing.

After a lot of chasing by myself and the garage, two missed deliveries, the breakers yards phone stopped working... According to the bank they never charged my credit card, which is something. Meantime, however, the garage had taken the engine out ready to fit the new one, so that will have added to the labour bill :( Needing to get it back on the road with the minimal of additional hassle as I was trying to sort things out over the phone while on holiday I ordered a new head from Turner Engineering, which was delivered quickly (thanks) and the engine was back in the vehicle last tuesday. Only it apparently won't start and there's only fuel getting to three of the injectors - so far the garage haven't managed to work out what's wrong.

I don't know which injectors are working and which aren't, it sounds like there's no diesel going to those injectors from the fuel pump from what the garage have told me. When the car went in it was running quite happily other than the steady stream of bubbles in the coolant. The only mild problem it had was a liking for a couple of shots of the glow plugs before starting (it would start on one, but not as easily) - the garage say all the plugs are working, but I guess this might have been down to the failing head gasket? So...it seems most likely to me that whatever is causing this has happened in the process of taking the engine in and out - any ideas?

Hopefully they'll get to the bottom of this soon - the cars been off the road for two clear months and in the garage for most of it. Whatever happens it's going, as it's had it's marching order from Erica - I was made to go out and by a eurobox to replace it at the weekend :( I'm going to be land rover-less for the time being.

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