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Thermostate what brand i should buy

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Old Aug 13th, 2018, 17:21   #11
canis
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Originally Posted by ITSv40 View Post
The OP's car is behaving perfectly normally. Having switched off the engine and the car is stationary, the underbonnet temperature will rise and possibly activate the cooling fan to reduce the temperature. The length of time the fan runs is dependent on a, the engine temperature and b, the ambient temperature. That is why there is a yellow warning sticker under the bonnet stating: Self starting fan, keep hands clear.
The sticker is there because the fan remains live even with the ignition off, so potentially can start. The cooling fan isn't there to cool the engine down. Water does that. The fan is there to supplement air flow over the radiator when stationary, to radiate away the heat from the water contained within.

Furthermore, there's a misnoma occurring here. The "thermostat" isn't even what switches the fan on and off. That is the job of a rheostat which is housed inside the radiator. It measure water temperature, not air inside the engine bay, so this "engine bay will get hotter" is false. Whoever heard of an engine getting hot when it's switched off anyway?

There is also the OP's original post where he seems to imply the fan starts only after the engine has been stopped, which is certainly a fault. Which is why I requested more detail.

None, absolutely none, of any of my cars have ever decided they're too hot when switched off. Ever.
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Old Aug 13th, 2018, 21:17   #12
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It is impossible for the engine to get hotter after you turn the engine off as illustrated by the first law of thermodynamics.

However if you have been driving, especially at speed, then you have gone from a situation of high air flow, high coolant and oil flow to suddenly zero of all of these. Therefore all the heat in the hottest part of the engine will transfer to the cooler parts and the coolant, so parts of the engine will get hotter after you stop! As will the engine bay.

I don't know where the temp sensor is for the radiator fan but they are often no longer on the radiator as they commonly were. If its on the engine then it could well trigger after engine shut off.

However on my diesel it is extremely unusual for the radiator fan to come on unless the aircon is on and you are stationary.

It would not hurt to check or just replace the coolant temperature sensor. They do fail and they do behave erratically towards the end of their useful life.

Some of them have separate outputs (more than two pins on the sensor) for the ECU and the instrument cluster and one or both outputs could be faulty.

Best thing to do is have a look around the engine bay and see if you can see a sensor on the radiator or on the cooling system somewhere else (or maybe it has both). Check the wiring and connectors and test with a multimeter.

As it has been said, problems with the MAF sensor can trigger the fan to run as you describe. Have you tried the advice on that?

Something like this

http://cpc.farnell.com/duratool/d030...BoC5i0QAvD_BwE

may be useful for verifying temperatures in the absence of being able to access a diagnostic computer.

If you coolant temperatures really are too high then you know you need to overhaul the cooling system, if not then you need to go testing sensors and chasing electrical faults.
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Old Aug 14th, 2018, 00:16   #13
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Originally Posted by bobthecabbage View Post
if you have been driving, especially at speed, then you have gone from a situation of high air flow, high coolant and oil flow to suddenly zero of all of these. Therefore all the heat in the hottest part of the engine will transfer to the cooler parts and the coolant, so parts of the engine will get hotter after you stop! As will the engine bay.
Quite agree. It wouldn't trigger a rheostat installed in a the radiator, but ...

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I don't know where the temp sensor is for the radiator fan but they are often no longer on the radiator as they commonly were. If its on the engine then it could well trigger after engine shut off.
Now that you mention it - you're quite right. There isn't one on the radiator. So where is it then?

I took a look through the wiring diagrams in the Haynes manual. There are two types listed; Fenix 5.1 and EMS2000. The latter type uses two relays so the fan can operate at two speeds. The former has only one. But in both cases they are operated by the fuel injection system.

So there we are, that's solved then. The fan comes on when the computer says so it'll be the computer making incorrect decisions. Which either means it's damaged, or it's getting bad information from a sensor.

Somebody mentioned MAF?

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Originally Posted by bobthecabbage View Post
It would not hurt to check or just replace the coolant temperature sensor. They do fail ... <lots more good stuff snipped for brevity>
Yes, and that one.
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Old Aug 14th, 2018, 16:58   #14
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Gatos nailed it when he said unplug it and see, so have you?
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Old Aug 15th, 2018, 13:56   #15
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Although this may not be your model the System follows the same........
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File Type: jpg Cooling Fan Control.jpg (215.8 KB, 12 views)
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Old Aug 15th, 2018, 22:19   #16
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Interesting!
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Old Aug 17th, 2018, 21:37   #17
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Sorry for late reply, i havent tried to unplug MAF yet, but im gonna try cleaning it with Denatured Alcohol https://en.wikipedia.org/wiki/Denatured_alcohol
Looked somewhere about cleaning(Hope its safe)... not sure how is it gonna go. But im going to trip Sunday something like 530km and than in 3-4days back,same 530km.

I have another question what is max. speed that can achive Volvo V40 1.9D 75kW 102PS 2001?

Back to Orginal question i tested i think today so i park the car in wait around 2-4minutes before kill engine during this time it tourns on cooling,LOUD noise. When it turns off, i turn off engine. And than after like a minute starting to hear the FANS again.
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Old Aug 17th, 2018, 22:01   #18
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Originally Posted by nandor90 View Post
Sorry for late reply, i havent tried to unplug MAF yet, but im gonna try cleaning it with Denatured Alcohol https://en.wikipedia.org/wiki/Denatured_alcohol
Looked somewhere about cleaning(Hope its safe)... not sure how is it gonna go. But im going to trip Sunday something like 530km and than in 3-4days back,same 530km.

I have another question what is max. speed that can achive Volvo V40 1.9D 75kW 102PS 2001?

Back to Orginal question i tested i think today so i park the car in wait around 2-4minutes before kill engine during this time it tourns on cooling,LOUD noise. When it turns off, i turn off engine. And than after like a minute starting to hear the FANS again.
Please don't spray anything onto your Air mass meter , it is very likely you will damage it ! It could be an expensive business as they are over 200 new . They are self cleaning and are fed with filtered fresh air from the air cleaner .
Also no need to worry about your fan it is not a problem at all . you will find when the colder weather arrives it won't run at all .
max speed ? about 115 mph I guess .
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Old Aug 18th, 2018, 08:13   #19
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Please don't spray anything onto your Air mass meter , it is very likely you will damage it ! It could be an expensive business as they are over 200 new . They are self cleaning and are fed with filtered fresh air from the air cleaner .
Also no need to worry about your fan it is not a problem at all . you will find when the colder weather arrives it won't run at all .
max speed ? about 115 mph I guess .
Well thats what everywhere states but someone said doesnt matter how much they say it can go much faster than that

So i tried unplugging MAF and turning on car it does work. the question is why? Is it safe driving without? Didnt try to unplug when engine running. Tried the cleaning couldnt assembly tools missing... have torx screwdrivers but cant acces So i will try this when i arrive home. HUN to SRB

Last edited by nandor90; Aug 18th, 2018 at 09:33.
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Old Aug 25th, 2018, 15:09   #20
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Changed fuel filter didnt see diffrence in driving. But had a problem 1st assembly fuel leak. 2nd the IN pipe fall out. Kinda was scared driving it back... Cause of what if... Didnt notice leakage since it. After 1300KM and driving around 140-170 mostly 160km/h there is a missing oil. Using Shell Helix Ultra Diesel 5W40, any reccomendation to what brand i should swap this out next time? Also for like 1h 20min driving at border the cooler on idling turned on and off 5-6x it was wierd for me. Next i dont have on car key trunk opener. Somewhere i read if i open doors i just need to push in trunk and it opens. But it doesnt opens, i couldnt open trunk to police officer at border.
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