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rover_45
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Discussion Starter #1
Had a run down to the Festival of Transport at Weston Park today and me and the 45TD (02 plate 83k) had the pleasure of sitting in a 2 mile queue on the A5.
The motor was fine and although I never heard the fans come on the temperature gauge sat steady in the middle.
£7 lighter of pocket I got to park up and noticed steam coming from the back edge of the bonnet. Opened the lid to see the expansion tank absolutely full and pushing water out of the cap (still no fans running). Avoided the temptation to meddle and left it to cool down while I had a mosey round the show but it was bugging me so I cut short the visit and headed back to the car 90 minutes later.
A few checks: oil level's fine, no water in oil nor oil in water and the fan fuse in the box under the bonnet is intact so after putting a litre of water in I head back for home (giving the M6 a miss). Motor runs as well as ever and 15 miles up the road I stop and check the coolant level. That's OK.
Got home and pick up with the decorating and also clear enough space in the garage to get the car in with a view to checking the fans tomorrow. Pop the lid and the expansion tank is now empty, that'll be another litre of water please. Top it up, run it to hot and it's fine.
Now: I know the coolant level was OK when I left home this morning because I checked. I don't ever remember the fans coming on but hey winter's only just over and I didn't buy the car until December and the engine on my old 400SLDi never really ran hot.
Checking the fans is normaly a question of shorting out the switch but where is it? My old (400) manual suggests a radiator mounted switch but I can't see this on the 45 although the sender for the temp gauge and ecu appear to be in the same place on the outlet on the head.
Any ideas?
Also is there possibility that all this has been caused by the expansion cap not sealing properly? The cap seems fairly robust (Honda?) but if it didn't seat properly the water would expand (not being pressurised) and run past it while the gauge (and fans) would sense water within a normal temperature range.
Does that make sense?
 

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other_manufacturer
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the L series is a tough old boot and is 100% rover.

you are right in your assumption in the water escaping through the cap - - replacements are cheap enough.
 

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As well as a new cap, I would check the coolant strength. On my old L series 220SDi, the coolant was boiling past the cap, and a new one didn't help. Increasing the mixture to the recommended 50:50 did though (and was fine for thousands of miles after, until I sold it). Plain water has a lower boiling point then antifreeze mix, which is the reason mine was boiling over.
 

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the L series is a tough old boot and is 100% rover.
Dead right there. My coolant cap came off this weekend on the M5, and the car lost a lot of water and overheated and cut out. The recovery guy refilled it with water after letting it cool a bit, and it appears to be absolutely fine.

Not so sure a K series (or many other engines in fact) would survive this treatment.

The most annoying thing was that the recovery guy who almost insisted on towing me only put about a can of coke's worth of water in, so the tank looked full, despite a massive airlock. I managed to put another 2 litres in from his container before driving away. If I had let him have his way, I might have needed a tow when it overheated again due to lack of water, if it had caused more serious damage than the first time. I'm with Britannia Rescue BTW.
 

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I'm no expert on the 45 I'll be the first to admit. However if you have aircon you can at least test the fans but turning the air-con on with the engine running. This should start the fans spinning (so you can at least prove to yourself they work).
I think the fans are controlled by the ECU rather than a thermostatic switch in the radiator (not sure though - but if there are no wires leading to the radiator then that would indicate the same). If this is the case and the gauge didn't indicate that the car was hot then I'd change the temperature sensor in the engine. A sensor is typically about a tenner from a motorfactor.

Usually if you remove the plug from the temp sensor with the ignition on, then the ECU detects a faulty sensor and switches the fans on as a safety measure, however on the 45 this may also illuminate the ECU warning light.
 

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rover_45
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Discussion Starter #6
Thanks for the help.

Never thought of running the air con - I've lived without it all these years and, although I do run it occasionally to 'maintain' it, it's not something that springs to mind automatically.

If the ECU warning light comes on when disconnecting the temp sensor will it extinguish when its reconnected or do I have to take it somewhere to be reset?
 

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Whether the light extinguishes or not depends on the age of your car I think. The earlier 200's the light would go off as soon as the fault was corrected. On the later OBD compliant 45's you'd have to have the light reset. the early ones aren't OBD complient so the lamp should go out. I've no idea which yours hence the warning!
 

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Thanks for the help.

Never thought of running the air con - I've lived without it all these years and, although I do run it occasionally to 'maintain' it, it's not something that springs to mind automatically.

If the ECU warning light comes on when disconnecting the temp sensor will it extinguish when its reconnected or do I have to take it somewhere to be reset?
My ZR is a 2002 model. Running the engine with the connector from the ECU temp sensor in the coolant elbow disconnected should cause the fans to come on, but does not illuminate the ECU warning light. If yours is a 2003 or earlier model then it should be fine. The elbow is right next to the 1st glow plug, left hand side if you're looking under the bonnet.

I would be surprised if it even lit the light on the later models, but wouldn't want to put money on it not happening.

I would say your fans probably come on when they should do. If the gauge is in the middle, the engine may not have reached the "fan switch on" temperature yet, and something mechanical or chemical is causing the boiling over, such as a weak coolant mixture, or dodgy pressure cap.

There is always the water pump, but this is very rare. Could also be the thermostat, but with a normal gauge reading it is unlikely imo. By the way, my gauge starts to move off the bottom after a mile or mile and a half or so of town driving in this mild weather, and the thermostat is working normally to my knowledge.
 

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rover_45
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Discussion Starter #9
It looks now as though this was purely due to the cap not seating properly on the expansion tank.

I've put a new cap on and added half a litre of that exciting Barbie coloured antifreeze and all seems well.

Must have been having a 'senior moment' on the fan subject because, although I've yet to test the switching, I never thought of running the aircon to see that fans themsleves worked (which they do) - thanks E_T_V!

Even though it's a 2002 model I'm cautious about upsetting the ECU/MIL and I'll just leave it idling for a few minutes after a journey and (hopefully) see the fans switch in of their own accord.

Interestingly the motor often runs like a pig for a few minutes after being stuck in traffic for a short time mainly, I suspect, due to heat build up in the engine bay and not helped by having the EGR disconnected. Maybe having the aircon running will help waft some air through the intercooler.....at least until I can re-route the air intake.

Thanks again
 

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Even though it's a 2002 model I'm cautious about upsetting the ECU/MIL and I'll just leave it idling for a few minutes after a journey and (hopefully) see the fans switch in of their own accord.
You could be waiting a long time. If your cooling system is in tip top condition then it might not happen. On mine, the fan will kick in for literally 5-10 seconds if I stop after a run, and not normally come on again. The thing that made my coolant boil over in my old SDI with the weak mixture was running it at a fast idle (1500-2000 rpm) for 10-15 minutes while I had some engine flush in it during an oil change. Give it a try if all else fails.
 

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Interestingly the motor often runs like a pig for a few minutes after being stuck in traffic for a short time mainly, I suspect, due to heat build up in the engine bay and not helped by having the EGR disconnected. Maybe having the aircon running will help waft some air through the intercooler.....at least until I can re-route the air intake.

Thanks again
I think having EGR connected would actually make things a bit worse, as there will be less fresh air flowing through the main inlet route through the turbo and cooling things down with EGR running (approximately half as much fresh air flow)
 

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Hi, can someone just clarify where to disconnect the temp sensor wire to test the fan, would be nice to see if mine has been or will work when needed.
Thanks
 

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rover_45
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Discussion Starter #13
Take the acoustic cover off the top of the engine, on the far left of the engine (as you're looking at it) - alternator/vacuum pump area - you'll see the outlet elbow for the coolant bolted to the cylinder head.

Set into the top of that is a switch with a wiring connector - that's what you're looking for. The switch and wiring on the underside of the outlet is the sender for the temperature gauge on the dash.

Do be careful when you disonnect the plug - if you're brutal they can break.
 

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Take the acoustic cover off the top of the engine, on the far left of the engine (as you're looking at it) - alternator/vacuum pump area - you'll see the outlet elbow for the coolant bolted to the cylinder head.

Set into the top of that is a switch with a wiring connector - that's what you're looking for. The switch and wiring on the underside of the outlet is the sender for the temperature gauge on the dash.

Do be careful when you disonnect the plug - if you're brutal they can break.
Yes spot on. If you want to test the sensor readings, an easy way is to test the resistance with a multimeter (about £10-20 if you don't have one, and has many other uses).

A guy on another thread came up with these values on a K series petrol, but they seem similar to what mine were (definitely at 20 Degrees anyway):

2 pin sensor, Should read (with cable disconected) 5900 ohms @ 0°C, 2500 ohms @ 20°C, 1180 ohms @ 40°C, 600 ohms @ 60°C, 330 ohms @ 80°C.
Remove sensor and test in water of varying temperature.

I didn't bother removing mine to test by the way, just used a temperature probe I have for work. If you don't have one, I could suggest testing it 1st thing in the morning (10-15 degrees ish at the moment), and then after a normal run of at least a few miles (temperature gauge in normal position)- the temperature immediately after switching the engine should be about 75-85 degrees C.

And watch you don't burn your hands if you test it hot!

Hope this helps,
Tim
 
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