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Coolant Temperature Sensor


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#1 Leevis

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Posted 02 June 2008 - 10:20 AM

Hi All
Coolant Sensor time again. Been on here before with an annoying cooling fan issue which is that it has fallen off. Trying to get the screw out of the motor currently so i am getting there.

I need to get this coolant sensor problem sorted. Basically i have the 'STOP ENGINE TEMPERATURE' alert on my 1.6SX Pic with Air Con Year 2000 X Reg. Its really annoying and i thought i had solved it by changing a part (a blue sensor) and disconnecting the battery and reconnecting etc. But this now doesnt seem to want to work either.

The problem i have is 'What is causing the STOP ENGINE TEMPERATURE alert?' Obviously it is a sensor of some kind but i am having difficulty identifying which one it is.

If you look at the picture DSC00032, this is an overhead view of the engine. There are 3 bits i need identifying here.

Attached File  DSC00032.JPG   179.45KB   329 downloads
Attached File  DSC00033.JPG   101.21KB   191 downloads

1) Big Blue Sensor on the left hand side (I have replaced this one already but not too sure that this is the right thing)
2) Green Thing (no idea what this is or whether it is relevant)
3) Other Blue Type Thing. You can just about see this thing between the engine and the green thing. I think that this is the bit that needs replacing rather that the bigger blue bit on the left. Is this the bit i need to replace? If so, how the hell does it come out? the other picture shows it in more detail but i have no idea how to remove it as it seems in a nasty place to get to.

Anyone have any bright ideas on this one?

Lee
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#2 Charliee

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Posted 02 June 2008 - 04:21 PM

Yea, here's a good idea Lee, you've been telling us your fan was broken for ages.... perhaps your ECU knows this too and is trying to tell you to get the ruddy thing fixed!

#3 Leevis

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Posted 02 June 2008 - 04:28 PM

Working on the fan thing. Appreciate that this is likely to be the root of the problem here.

The question i am asking is, and probably not asking it very well, when the fan is fixed is this going to reduce the temperature? I really do not think so because it is on when the car is cold ie first thing in the morning.

I want to get some clarification on where the coolant sensor is, i read that it is the one that i have changed ie the big one on the top of the engine but i read somewhere else on the forum that when the sensor is removed some of the coolant will come out and that isnt happening on my PIC probably because i am not doing the right sensor and it is that 'other one'.

Can someone clarify what these 2 sensors are? I am well and truely confused on this one.

Lee

#4 Charliee

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Posted 02 June 2008 - 06:47 PM

Have a look here Lee,

http://smarttech.tec.../...view&id=181

tells you how to check sensor.
I wasn't joking earlier.... if you have had a cooling fault registered at some time in the past it may continue to show until reset by a diagnostic code reader, it may also be detecting an open circuit on your (removed) fan motor wiring.

#5 Leevis

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Posted 02 June 2008 - 07:27 PM

I know you wasnt joking and i appreciate your comments. I know that the fan is most certainly the cause of my woes. I just want to make sure that the 'sensor' that i have replaced is the correct thing that often seems to be at fault. I certainly know that getting the sensor changed isnt going to cool my engine :)

According to the attachment the sensor is located in cylinder head coolant outlet housing. I am not too sure exactly whether this means it in directly on the top or the one at the side (this is where i think it is) but i am a total div so far :) so i am not holding out much hope.

#6 kfk

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Posted 02 June 2008 - 07:50 PM

The large green connector in your bottom picture is for the oxygen sensor.....nothing to do with your cooling fan.



Can you PM me your chassis number.
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#7 kfk

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Posted 02 June 2008 - 08:28 PM

the blue sensor is the coolant temperature switch....it has an on off function and should be open circuit with a cold engine.....closed circuit between pin 2 and earth means you will get an overheating message.



the green sensor varies its resistance according to temperature and in addition to powering the cooling fan it will also provide information to the engine management system to help it decide if its doing a hot or cold engine and adjust the fueling accordingly.



Both green and blue sensors provide information to the injection ecu, the injection ecu will then instruct the cooling fans to work if required or send a message to the bsi which in turn will put a message on the display to give you something to worry about and hopefully cause you to check coolant!



If the vehicle has air conditioning it should be noted that if you turn aircon on the fan should operate regardless of engine temperature.....Does it?.....and if you turn it off does the fan stop?



The screw you are removing from your fan.....do you realise its a left hand thread?
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Wants some help, give me a clue.......petrol/diesel/engine size/year....Please post messages in main forum before asking me in Private Message

....Still waiting for proof that the customer is always right
....Has anyone checked the nut holding the steering wheel?

....Has anyone seen the crystal ball?

#8 Leevis

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Posted 02 June 2008 - 08:41 PM

kfk, thanks, i think i am turning very quickley into King of the Divs and will be forever known as coolant sensor man!
Both of my sensors are blue. One on the top and one on the side below the oxygen sensor which is the big green thang. I am a bit confused about which one is which.

I cant check if the fan operates when the air con is on because i have taken the motor off and its in my boot. But from memory, yes the motor spun when the air con was on.

I did realise it was a left hand thread, just to make it easier :)

#9 kfk

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Posted 02 June 2008 - 09:11 PM

.....must get my eyes tested!



the one that looks difficult to get at (2 pin connector) that will require removal of the air filter to access is the switched sensor....it screws in.



The upper sensor (3 pin connector) that you have already replaced is the one that varies resistance with temperature.
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Wants some help, give me a clue.......petrol/diesel/engine size/year....Please post messages in main forum before asking me in Private Message

....Still waiting for proof that the customer is always right
....Has anyone checked the nut holding the steering wheel?

....Has anyone seen the crystal ball?

#10 Leevis

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Posted 02 June 2008 - 09:18 PM

K so the one i need to replace (ultimately) is going to be the one thats a bit of a poo to get to.

#11 Guest_picowner_*

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Posted 18 March 2009 - 08:38 PM

K so the one i need to replace (ultimately) is going to be the one thats a bit of a poo to get to.



sorry ive got the samy problem dont mean to bump the thread but which one is the temp sensor ?

and this this fix your problem?

thank you

#12 Drift

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Posted 04 April 2009 - 11:14 PM

If I remember right its a 17mm spanner and it comes off easily, I changed my mates 1.6 petrol sensor in my lunch break, it only took 5 minutes, but a tip, the engine was a tad warm and I forgot to loosen the coolant cap so the the rest of the afternoon was spent sitting in my office smelling of anti freeze lol it makes a nice fountain lol
20hdi 54 picasso,2.8tdi Isuzu powered LWB Frontera lifted 2",32"mud terrain tyres and other stuff.

#13 Guest_chris5339_*

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Posted 23 April 2009 - 07:40 PM

Hi sorry to jump on this thread but i have a 1.8 16v pic and it has the same problem but there is only one sensor that i can see. Can anyone help :( it's a 03 plate.

#14 thegoat

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Posted 11 May 2009 - 04:13 PM

hi all
i've just changed the coolant sensor on my wife's 1.6 petrol pic, (the one fitted in the side of the cylinderhead )
no water came out when i changed it, surely the sensor is inside the water jacket, SO when you remove the sensor lots of water should come out,
am i right about that ?
if i'm right why did no water come out

#15 thegoat

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Posted 16 May 2009 - 01:35 PM

replaced the lower engine temp senser, and after a play round got the cooling fan running
the rouble is now the "stop engine temp warning message" is on the dashboard all the time and the temp gauge is at the top, but the engine is cold,
how do i reset these alarms

#16 Charliee

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Posted 09 June 2009 - 02:28 PM

Suspect this is playing up on my 2.0HDI.
Got stop engine/overheating warning today even though engine cool, and it won't stop this message. Should reset itself
So wondering about the 2 wires to sensor: seems to register hot when open circuit( ie plug off sensor), am I right in thinking that bridging the two would send a "cold" message and hence prove that sensor is at fault rather than a wiring/ecu problem?

#17 Leevis

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Posted 30 June 2009 - 10:16 AM

Buggeration

Fan has fallen off yet again :(

Just been to Citroen Dealer and bought the following

1. Plastic Bits for putting the liners back in under the wheels
2. The screw that goes into the front of the fan
3. The washer that goes with the screw

My plan is the same as last time, remove the bumper, take out the fan (which is just sitting in there), remove the motor, see what the problem is (most likely to be the head of the screw has come off again), get the hole re-threaded, replace fan. put bumper on, reset battery and hopefully the STOP TEMPERATURE WARNING alarm will cease.

I might even get a new motor

#18 Leevis

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Posted 30 June 2009 - 06:13 PM

Hmmm i think i have a problem and need some advice here.

The fan has been put on again (I am a bit of an expert at this now), it would appear that the screw holding it in had fallen out so it was as easy, apart from getting the bumper off.

Anyway, I put on a new heat sensor. This is the one which you can see on the pic, its a big blue one. Took the battery off, left it for 10mins or so, re-connected the battery but i am still getting the STOP ENGINE TEMPERATURE warning beep and message.

Anyone know what else i can do here, i did notice another blue sensor which seems to sit below the green one, but looks like its a complete arse to get at. Could this be what i need to change also?

Any help would be groovy as the noise is doing my head in.

I have some other pics of this other sensor if anyone needs them to identify what it is but i was under the impression that the top blue one was the culprit. Last time, i just reset the battery and all was cool again :)

Thanks

Lee

#19 Charliee

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Posted 30 June 2009 - 06:46 PM

The two leads that go to the sensor should show around 4 volts when pulled off and the ignition is turned on...... if this is so then circuit is ok.
You will also then get overheating message.
Make sure you then have a good connection to sensor - if you have a spare one try connecting it "loose" - ie not fixed in engine; if you have a good circuit, and a good sensor then the problem may be just the contacts in the plug betwen the two. I had to dismantle this and squeeze the terminals slightly for a cure.

#20 Leevis

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Posted 30 June 2009 - 07:10 PM

Hmmmm ok that sounds good i think.
Am i talking about the correct sensor though? The top one (blue).
This is a brand new sensor though, took it out of the packet and put it on straight away. However, i think that you mean the bit that connects to the sensor, i'll try that. Should i disconnect the battery also or would it show straight away?
Appreciate your help on this btw