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In my 2001 1.9DCi Megane: When the weather is cold I find that the engine temperature never gets up to the usual running temperature. This is especially the case if I have the cabin heater on to stay warm. Sometimes, when it is really cold and I turn the heater up you can almost see the engine temperature dropping, and feel the heater cooling off. Also the car takes a good while to warm up. The thermostat is working OK from what I can tell, as the radiator pipes are still cold when the engine has warmed up a little.

I've even been thinking of getting a webasto heater to warm things up a bit. Or blocking off some of the vents in the front of the car like you used to on landrovers in the winter!

Any suggestions would be welcome.
ALi
 

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Dunno how many rad fans you've got but I had the same problem in my Scooby. It was because the Air Con fan was working constantly when it shouldn't have been!
 

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Engine thermostat stuck open?

Sorry u have done that, our dci Clio starts to get warm
in this weather after 2 miles but takes 7 or 8 to get up
to normal it then stays there no matter what the heater
is set to, modern Diesels dont burn enough fuel to get
up to temp fast in really cold wx, that's why some cars
have systems that heat the water on start up some
Renault's have this, there's a unit on one of the big hoses
that as what looks like 4 temp sensors in with wire going
to each but not all have them mine doesn't.
 

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Hi,
Thermostats get lazy as they age. Opening temperature might be near normal but they tend to close at a much lower temperature. Mine closed at 82C, see post:
http://www.renaultforums.co.uk/showthread.php?t=53965
The ECU might record a fault stating that the normal operating temperature is not reached.

TK
 

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Discussion Starter #7
How did you test the thermostat:)
I waited until the engine had warmed up a little, and then felt the pipes to see if they were warm as this would show that water is flowing through the radiator due to the thermotat opening.

As for the thermostat being lazy to close in theory there should be no real problem there as it shouldn't open at all and therefore can't close again until things have hotted up!

I might take it out and check to be sure.

Morning drive is about 30mins of country roads (14miles). It has warmed up a bit after 10 mins or so, but even on a long journey the temp usually only gets up two divisions, and summer running temp is the third one. If it's really cold it'll only go to one division.
 

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Hi Al,

I have just been out with my Kangoo - first drive after renewing thermostat and glowplugs. Before the temp gauge indicated to the 3rd dot, now it goes to the 6th dot, 2 dots below the double dots. As stated in my post, aged thermostats get lazy and tend to close at a much lower temperature than the opening temperature and the engine will run cold. Opening temperature may be higher than the specified opening temparature. Engine operating temperature will be near to the closing temperature. I suggest you make a trip to Renault and buy a new thermostat. Mine came as a complete unit - thermostat housing containing thermostat and sensors. Renault turned out to be cheaper than motorfactors as theirs did not have the sensors fitted.

TK
 

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Another point I should have made in my previous posts. The thermostat is the only device that controls coolant temperature. Radiator fan has nothing to do with it; it only assists getting rid of excess heat. Sensors only meter temperature but does not control anything. Your thermostat is fubared as the Americans say. Have it replaced and your problem is solved.
By the way, on older cars you could replace a thermostat wearing your best white shirt. Not so on a Renault. I did it on mine a few days ago. It was a rather fiddly job due to poor access.
 

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Good advice Tolsen - the only thing you have to remember with radiator fans on some renaults is that they are controlled by the ECU and there have been cases where the fan runs continously because there is a fault in the air-con system - so it worth while checking it anyway just in case as no doubt it would pull the temp down uneccesarily. And as it runs at a relatively slow speed it is hard to detect at times. Plus it is easy to check it out.:)
 

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Sensors only meter temperature but does not control anything.
Gotta disagree there tolsen. In my previous Laguna my Temperature Sender was fubar and this did control something......it sent messages to the ECU to help with the decision making of how much fuel air mix should be dealt......as the sender was fubar I was having all sort of unmerry problems :rolleyes:

Also, if your rad fan sensor is fubar, it'll not work your engine fans and, therefore, lead to your angine overheating as the excess heat will not be gotten rid of, as you rightly stated.

Just pointing that out as your post, although maybe not meant, could be construed as 'not to worry' about these items :)
 

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Gotta disagree there tolsen. In my previous Laguna my Temperature Sender was fubar and this did control something......it sent messages to the ECU to help with the decision making of how much fuel air mix should be dealt......as the sender was fubar I was having all sort of unmerry problems :rolleyes:

Also, if your rad fan sensor is fubar, it'll not work your engine fans and, therefore, lead to your angine overheating as the excess heat will not be gotten rid of, as you rightly stated.

Just pointing that out as your post, although maybe not meant, could be construed as 'not to worry' about these items :)
My apologies,

What I meant was the temperature sensors do not control the engine temperature. This is done by the thermostat.

Regarding controls, the sensors do actually not control anything, they read physical properties and convert these to an electrical signal or voltage. The control is done by a control unit, which on an engine will be the ECU.

Apart from a fubared thermostat, the only other cause of low running temperature is that the engine does not produce sufficient heat, i.e. not running on all cylinders.

TK :d
 

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Discussion Starter #14
tepid!

Hi, interesting discussion!! Anyway, the fan doesn't operate, and as I mentioned before, the radiator doesn't warm up suggesting there is no warm water flowing through it, suggesting the thermostat hasnt opened.

As for the talk about sensors etc there is a separate sensor that switches on the rad fan (i adjusted it to come on at a cooler temp in my old skoda to stop it overheating). In many cars this fits into the end of the radiator

As diesels generate very little heat, especially the 1.9 engines the physical air flowing through the engine bay may cool the engine down, especially in really cold weather, and if you put the heater on this takes more heat away from the engine too and will cool it further. Apparently the 2.0 litre VAG engines are now much better at retaining their heat!

I'm going to take out the thermostat and check it over anyway. Luckily I have good old Haynes to guide me through, and it looks no where near as nice a job as my previous cars!
 

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My apologies,

What I meant was the temperature sensors do not control the engine temperature. This is done by the thermostat.

Regarding controls, the sensors do actually not control anything, they read physical properties and convert these to an electrical signal or voltage. The control is done by a control unit, which on an engine will be the ECU.

Apart from a fubared thermostat, the only other cause of low running temperature is that the engine does not produce sufficient heat, i.e. not running on all cylinders.

TK :d
;) :)
 

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You can talk about cooler diesel engines and air-flow but the thermostat should be able to compensate for any heat loss - well in our climate anyway. In other words if the cooler air-flow reduces the temperature the thermostat should close to compensate.
Apart from lower combustion temperatures diesel engines are normally harder to warm up because they have thicker and stronger components - more metal to heat that is. This problem has diminished over the years as advances in technology have improved - such things as lightweight diesels and multi-injection phasing:)

One other thing that can cause a temp gauge to show lower temperatures than is actually in the engine is an air-lock
 

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One other thing that can cause a temp gauge to show lower temperatures than is actually in the engine is an air-lock
Madnoel knows his stuff!

A good point which I never thought of. There is a bleed cap at the top of your thermostat housing. It is just a valve cap - exactly same as on your tyre valves. Unscrew reservoir cap when engine is cold, then open bleed cap and check if there is air in your system.

TK :d
 
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