When driving down the motorway my temp gauge was sitting in the middle but evey now and again it would climb slowly to the 3/4 mark before droppping back down to the middle. It did this about 4 times over a half hour period but only when cruising gently at about 70.

I checked the coolant level and bled any air out then took it out for a spin today with the hidden menu coolant temp pulled up. It sat at 112 - 114 during a hslf hour at varying speeds but mostly town / traffic. I thought that might be a bit high but the only reference I could find to normal running temp was about 112 so thought it was about right.

However, some knowledgeable souls have suggested that this may be too high and normal temp is high 90s.

As I've only just bought it from a trader I'm keen to get to the bottom of this asap in case there is a big problem.

Any advice / experience greatly appreciated.

Andrew
have a look here http://www.myrangerover.co.uk/MyRangeRover/RAVE.html this is the landrover/rangerover workshop manual. Will help with RR ownership!

I already had a copy of that. Unless I'm going blind/mad (both entirely possible) it still doesn't show the actual operating temperature range of the engine.

Once mine has climbed to the halfway mark mine rarely moves. Reformed

I couldnt find it either so was going from the top of my head so could be wrong on temps. Dan is an expert in all things RR so hopefully he will pop in to give his 2p worth.

I googled for M62 coolant temperature and found this:

http://www.meeknet.co.uk/E38/M62%20Engine%20Details.pdf

In the BMW application the coolant temperature is controlled depending upon engine load. Don't know if this is the same with the RR, but see graph on page 11 and explanation on page 10. Interesting even if not helpful in the end !

Nice find Ric

This, from p13:

Coolant temperature gauge
The indicator characteristics of the coolant temperature gauge in the instrument cluster have been adapted to the higher temperature level of the engine due to the use of the characteristic map thermostat. The pointer of the coolant temperature gauge in the instrument cluster is located in the mid-position at coolant temperatures of 75 o C - 113 o C

suggests that 112 - 114 is at the top of the range expected under partial load which is what I was doing most of the time.

This looks as though 110 is the normal operating temp. (my bold)

Due to the coolant heating up in the engine, a temperature of approx. 110oC is measured at the point the coolant flows out of the engine (installation location of coolant temperature sensor for DME and instrument cluster gauge). This is the operating temperature of the engine, at which the characteristic map thermostat begins to open without control intervention.

So in summary - the main thermostat opens at 110C, then if additional load is placed on the engine it lowers the effective opening temperature thereby allowing the coolant temp to fall as low as 80C without closing the thermostat. The temp gauge in the car won't budge as it sits in the middle between 75 and 113C so the happy driver won't know that any of this technical wizardry is going on.

Sounds as though I might not have too much of a problem but will pull the hidden menu coolant temp up next time I'm on the motorway and see what happens to the real temp if the gauge starts climbing again.

Oh, and one more thing....... Rob you're an absolute for making me think that my engine was about to explode. Damn near ruined my weekend.

Keep in mind the application being described there is the BMW E38, i.e. a 7 series car. It's the same engine but it might have been set up with different target operating characteristics. I'd still advise sorting the issue as the temperature shouldn't shoot around like you described.

True. Hopefully someone else can confirm the operating temp in a FFRR although I'd be surprised if it was significantly different at partial load due to it being the same basic engine.

So far the temp hasn't been shooting around all over the place, just the needle in the gauge. The diagnostic temp was very steady. Until the guage misbehaves while I've got the diagnostics up I won't know if there is a problem.

And I thought that owning a Lotus was scary enough.

Sorry wasnt ment in that way at all. I've lived with this for over 12months thinking mine is about to go bang due to loosing coolant etc. They may be the ranges of the stat but they do seem high as mine for example are a fair bit lower. Look for swast4 (Adam) as I work with him and he has had a HGF and his post rebuild runs round the 98 mark. Look for him on rangerovers.net as he's gone into the cooling system quite a bit for cooling his engine down. I had a quick read of that bumf and can't decide what to think. Granted I've had a few beers.

Bit more reading for you. http://www.rangerovers.net/forum/viewtopic.php?f=2&t=33023
From that it looks like its a 105C stat but controls as an 85C due to the elcetronic bit. Note in there they reference 110C being classed as overheating?????

Change your radiator. Or at the very least remove it for inspection and a clean/flush. Not sure you should be reading this bit.

Here's my thoughts on what could be happening:

Under normal conditions the wax stat will be partially open, giving you normal flow through your radiator. In our climate the stat will rarely be fully open as the cooling system has to have the capacity to be able to deal with hot climates - think towing your caravan in the Sahara.

When you put increased load on the engine (not necessarily increased revs) the ECU detects the increased load and sends a signal to heat the thermostat to force it open in anticipation of an increase in coolant temperature.

However, in your instance I would guess that your heater circuit has failed (not uncommon) this then means that you get a short delay from a hot spot developing in the engine, the coolant temperature rising and the stat opening fully.

This won't illuminate the MIL but it will have stored a fault code - get it to an indy and get it checked out. I believe the stat housing contains the heater element so is a fairly easy/relatively cheap fix.

Hope this helps.

Dan

ps, some people wire their stat heater to be fully open, this results in increased warm up time, shortened cat life and poor fuel economy. The electronically controlled stat is a great piece of engineering - don't be tempted to "mod" it. 

Thanks Dan

I've just got back from a test drive with the temp diagnostic on (before reading your post) and it was behaving exactly as you described. Under increased load (up hills, higher speeds) it would gradually creep up to 117 - 119 before dropping sharply down.

From a warm start-up it got up to 112-114 reasonably quickly then sat at that temp quite comfortably. In stationary traffic it was staying in that range and the electric fan was kicking in when necessary. This suggests that the fundamental cooling system is ok.

From what you describe, the additional temeratures caused by an increased load would give rise to a sharp increase in temp and the thermostat can't open quickly or soon enough to deal with it.

The car is under warranty so I'll get it checked in asap for the fault codes.

I'm assuming that although the thermostat should hold a 110C temp the fact that mine is normally 111-114 is nothing major to worry about? If the fault is the component that you describe then again I assume that both bits will get swapped out anyway so I may see a slightly lower temp nearer to 110 with new components?

Update:

You're a genius Dan.

Got the code pulled this morning and there is an electrical sensor fault. Booked in for next Wednesday under warranty.

For those who are interested, whilst plugged into the diagnostic computer it was shown as running at 109C, whilst the hidden menu was showing 112C. The technician said that the on board one is often a few degrees out and that 110C is the normal expected running temperature of the engine and there is nothing to be worried about if the OBC shows a couple of degrees above that.

Hopefully this info will help others in the future.

As I now can't drive it for over a week I shall dedicate my time to polishing out all the scratches in the paint.

Thanks again to all for your advice.