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Discussion Starter #1 (Edited)
Hi All,

the temp gauge on my 2006 T5 is different to my previous T5 and pretty much any other modern car I've owned / driven.

On my last t5 (and golf, my works caddy, other makes etc) the gauge goes to 90 after warming up and stays there unless I'm ragging it.

On my current T5 the gauge goes to about 70 and stays there if i'm driving about town. it creeps up to 80 if i'm on the motorway, and goes to 90/95 if I'm chugging up hills on the way to devon.
Also, if I'm going down a long hill, like on the way back from north devon to the M5. the temp will drop all the way to 50.

As the van is nearly at 200k and is using a bit of coolant, I suspecty a previous owner has bodged something to mask an underlying problem

What should I be looking at here?

the fan works, and I can hear the aux water pump running on after I switch off the ignition, so both of those seem to be doing what they should.

cheers :)
 

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If it's a 1.9 then it's on the front almost behind the back of the alternator so not bad, 2.5 is down the back behind the turbo inlet elbow and a little more awkward

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It's down the front under the oil cooler on a 2.5 James, and a right evil job too!

When the temp drops to 50 degs on the motorway is the heater still hot? If it is it is probably just the temp sender, if not thermostat assuming you have no other cooling system problems (water loss etc).
 

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The ac pump sits under the oil cooler, the lower coolant pipe to the rad runs down by the side of it. But its round the back under the turbo on mine and my mates axd's

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Discussion Starter #8
it's a 1.9.

I guess it was optmistic to think it'd be at the top of the engine :) swapped one on an A Series engine earlier this year, took about 20 seconds.

I'll remember to get coolant - before- I drain whats in it now.

re: water loss - it's using a bit, the level in the header tank drops for the top line to the bottom line after about 600 - 700 miles
 

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If the heater is getting fully hot at any time at all it's probably not stuck upen but it won't hurt to chnage it to be sure. A stuck open thermostat won't cause water loss though so have a very careful look under the drivers side for any possible water pump leak and also check the auxillary pump because they can drip.

I only ever hear the aux pump on mine on very hot days. I wonder if your auxillary pump is stuck on and causing overcooling.
 

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Discussion Starter #10
If the heater is getting fully hot at any time at all it's probably not stuck upen but it won't hurt to chnage it to be sure. A stuck open thermostat won't cause water loss though so have a very careful look under the drivers side for any possible water pump leak and also check the auxillary pump because they can drip.

I only ever hear the aux pump on mine on very hot days. I wonder if your auxillary pump is stuck on and causing overcooling.
yes, the heater is definatly working, and also, if I turn the dial all the way to 'cold' the temp shows higher readings, so the coolant going through the heater matrix is having an effect, so at least I know thats not blocked.

Good idea on checking the aux pump though, I'll get under the van and have a look when it stops raining.
 

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The heater setting shouldn't have any real noticable effect on the temperature gauge if everything else is working as it should. The temp gauge should climb gradually up to 90 (depending on load (hills/big throttle) and stay bang on that just as your experience of other cars says apart from in very cold weather and/or long downhills. It is true that if you put the heater on hot and turn the fan to max fan it can lower the temp of the coolant but it is a small amount and the ECU 'tells' the gauge to ignore these small normal variations. That is why modern vehicles (that actually still have a temp gauge) always show a nice rocksteady temp unless a real problem exists.

I think your problem could possibly be the head gasket. On a petrol engine any changes to the normal flow of the coolant circulation caused by combustion gasses escaping into the coolant soon shows up by obvious overheating even at idle. But diesel engines lose heat more efficiently so can mask the normal obvious symptoms. It is an unusual synptom but I think it's possible. 19's are known for head gasket leaks and at 200k you'd have to forgive it! Obviously it pays to eliminate everything else you can first but it would explain the coolant loss too. Any residual pressure in the coolant bottle when stone cold in the morning?
 

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Discussion Starter #12
The heater setting shouldn't have any real noticable effect on the temperature gauge if everything else is working as it should. The temp gauge should climb gradually up to 90 (depending on load (hills/big throttle) and stay bang on that just as your experience of other cars says apart from in very cold weather and/or long downhills. It is true that if you put the heater on hot and turn the fan to max fan it can lower the temp of the coolant but it is a small amount and the ECU 'tells' the gauge to ignore these small normal variations. That is why modern vehicles (that actually still have a temp gauge) always show a nice rocksteady temp unless a real problem exists.

I think your problem could possibly be the head gasket. On a petrol engine any changes to the normal flow of the coolant circulation caused by combustion gasses escaping into the coolant soon shows up by obvious overheating even at idle. But diesel engines lose heat more efficiently so can mask the normal obvious symptoms. It is an unusual synptom but I think it's possible. 19's are known for head gasket leaks and at 200k you'd have to forgive it! Obviously it pays to eliminate everything else you can first but it would explain the coolant loss too. Any residual pressure in the coolant bottle when stone cold in the morning?
well, more deveopments. I topped up the expansion tank last week, as it was going low as usual, but the dash light came on yesterday, so I topped it again thinking I may not have put enough in, but it lit again after 30 miles today, so I am now losing coolant at a bigger rate.

I've had a look under and I can see and smell some coolant drips below the expansion tank, but can't see anything actually dripping whith the engine running.

I'm hoping it's a rad leak or something equally as easy to fix, but deep down I know that at 200k the head gasket is probably on its last legs too.

my current plan:

take the front bumper off and have a good look at everything with the engine running.

I've also ordered a new expansion tank (as the one fitted is rusty on the sensor, which can't help) anbd a new thermostat (and gasket), Im also going to order a new rad, once I've seen what condition the existing one is in.

Is there a 'hose / pipe kit' that anyone would recommend too?

I have the luxury of a second car I can use, so I can take my time replacing parts with the van stored off road.

If none of that helps, at least when I get the HG done, I'll also have a renewed cooling system ...
 

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Discussion Starter #14
also also,

I suspect there is more than one issue with my engine, so I just need to be methodical and tick stuff off as I go :)
 

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Discussion Starter #15
no residual pressure when unscrewing the coolant cap though, no mayo on the filler cap, and the dipstick oil smells 'normal'
 

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No pressure after standing is a good sign. Swap the thermostat out and fix the leaks fingers crossed for you

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Discussion Starter #17
Spent all morning taking the bumper off to get a better view of the rad (and see whats needed for when I replace the rad, which i've also ordered) and I think, with all my fingers crossed, that the water may be leaking from where the temp sender is on the bottom corner of the rad. I ran the engine for half an hour and it didn't drip anywhere I could see, but there is red stains from antifreeze higher up in the engine bay, so I'm hoping that when its warmed up, its weeping from there and being blown up into the engine bay by the wind. I wiggled the sensor and it made a gurgling noise as if it was letting air in, and when I removed the C clip, it was pretty loose.

re: the thermostat, I can see the plastic pipe that mounts to the front of the block behind the power steering or aircon pump, it looks fiddly, any tips ?

I have the BRS engine.
 

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Funnily enough, I realised our T5 1.9's thermostat was gone on the same bit of the North Devon link road..!!

I hate to say it, but if you have coolant splashed further up, it maybe the classic 1.9 head gasket. Pop some rolled up tissue into the vent holes under the expansion tank and see if they get wet and pink - i.e. the system is over pressurising and venting.

Could still be other causes, but normally HG. sorry
 

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Spent all morning taking the bumper off to get a better view of the rad (and see whats needed for when I replace the rad, which i've also ordered) and I think, with all my fingers crossed, that the water may be leaking from where the temp sender is on the bottom corner of the rad. I ran the engine for half an hour and it didn't drip anywhere I could see, but there is red stains from antifreeze higher up in the engine bay, so I'm hoping that when its warmed up, its weeping from there and being blown up into the engine bay by the wind. I wiggled the sensor and it made a gurgling noise as if it was letting air in, and when I removed the C clip, it was pretty loose.

re: the thermostat, I can see the plastic pipe that mounts to the front of the block behind the power steering or aircon pump, it looks fiddly, any tips ?

I have the BRS engine.
Are you assuming the temperature sensor you mentioned in the radiator is the one that controls the temperature gauge in your dash ?
I have a feeling that the sensor in the radiator is for the ECU so it knows the temperature of the coolant leaving the engine or maybe it's the temperature of the coolant entering the engine.
There is another temperature sensor that controls the gauge in your dash. On my 2005 1.9 that sensor is behind & below the tandem pump on the L/H end of the head.
 

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This is the coolant temperature sensor on my AXC engine. The view is from the back of the engine, (you can just see the L/H end of the exhaust manifold in the right of the picture).
This is the sensor that controls the temperature gauge. Hopefully your engine will be similar.
184908
 
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