Engine Temperature sensor

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
Am I right in saying that it is a well know problem that the Engine coolant Temperature sensor goes faulty & sends the wrong reading to the ECU ?

Is there an error code stored in the ECU (as I want to prove to the warranty company thats what it is) if not what other way can you confirm that this where the fault lies ?

The symptoms are intermitant but are :

i) The Glow plugs lights stay on for 45-60 seconds (indicating to me that the ECU thinks the engine is VERY cold), then when you start the engine if Revs hard straight away then settles to a tick over of 1100-1200 RPM (should be 900RPM) which indicates to me that it could be Over fueling due to the ECU thinks the temperature is very low.

ii) Then on other occasions when car has been left out all night & is extremely cold the Glow plugs hardly come on at all & then when I start it "just about" stays running or when I move away will loose power until I let foot off the gases to allow it to settle & then its OK……this COULD be accompanied by a lot of white smoke.

I've got round this problem by continually turning ignition key off & on so that I get a short burst of Glow plug each time then after I've done this a number of times (ie I feel that the cylinders have been heated up) I then turn the key to start & its OK.

Paul
 

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
I know it's a fairly common fault on VWs, so quite likely that the same sensor is ued.
In fact a mate at work had one go on his Golf a few weeks back.

Symptoms certainly tie up anyway.
 

bizzy

Guest
I have just changed my temp sensor because my temp gauge used to move around when it wanted to and my glow plug light used to stay on for ages even when my engine was warm,it runs a lot better now and the mpg has improved.
It cost me £16 inc vat and took about 15 mins to change it.
 

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
I understood from elewhere in this forum that you can use the climate control display for diagnostics on various functions (using the recirc button & then the up arrow)........& that Channel 51 on this was "Engine coolant temperature in DegC".......................does anyone know where the sensor for this is situated because it doesn't agree with the Temperature gauge on the dashboard & also it doesn't seem to vary with the "wrong temperature" that is sent to the ECU.

So I suppose my question is :

Where are the following Enginer coolant sensors situated :
a) The one that shows up on the Climate control diagonstics
b) The one that shows on the temperature gauge on the dashboard
c) The sensor that gives the info to the ECU (which is the one on my car I'd think is faulty)

Paul
 

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
Gavin thanks, I've just put my car in for MOT/service so I've just told them to change the sensor but the garage wants to monitor what the sensor is throwing out.

I'm glad that I've found someone else who has actually used the climate control diagnostics one strange thing I've found though is that on occasions when I first do these diagnostics before starting the engine it already reads 24DegC...............& thats after 12 hours on a cold night..............so I wondered if this was some default if the sensor was wrong, other times it reads 14DegC...................but only these two 14 or 24 surely can't always be exactly those temps.

I also find that the temperature on channel 51 only "changes" as the engine gets warmer if the BLOWER ! on the climate control is blowing !!!!!!............have you found this ?..............this is what lead me to believe that the sensor for this was somewhere else related to the heater system & that when I set the clime to "HI" & but blower on opened some gateway into the heater coils.

Paul
 

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
Are you sure that the channel you're looking is showing engine coolant temp ?

From what I understand, the climatronic channels vary between different models (eg Ibiza, Leon, and other VAG cars) so what might be engine coolant temp in one car could be something completely different in another.

I think the Climatronic has a variety of temperature sensors to monitor air temps at various points, so just wondered if what you're looking at isn't the coolant temp at all :shrug:
 

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
I got the info on channel 51 from the same place as Gavin, anyway yesterday had the sensor changed (infact the ECU had the error "ECT Sensor short") anyway, the starting is less laboured now, more instantaneous (although I did get the VNT vanes on the turbo "exercised" at the same time to get rid of a little of the carbon) generally either/or both have made a lot of difference to the running.

I also looked at channel 51 after fitting.................& the DegC reading now is fairly progressing starts off at a decent temp & climes steadily to 90 DegC...........How it sticks at EXACTLY" 90 DegC all the time I don't know........not even varying +/- 1 DegC
 

jiege01

Toledo TDI
Jan 11, 2006
236
0
Magherafelt, NI
I understood from elewhere in this forum that you can use the climate control display for diagnostics on various functions (using the recirc button & then the up arrow)........& that Channel 51 on this was "Engine coolant temperature in DegC".......................does anyone know where the sensor for this is situated because it doesn't agree with the Temperature gauge on the dashboard & also it doesn't seem to vary with the "wrong temperature" that is sent to the ECU.

So I suppose my question is :

Where are the following Enginer coolant sensors situated :
a) The one that shows up on the Climate control diagonstics
b) The one that shows on the temperature gauge on the dashboard
c) The sensor that gives the info to the ECU (which is the one on my car I'd think is faulty)

Paul

a- dont know
b- bottom right handside of the bumper near the fog light.
c- side of the engine, followin top radiator coolant pipe back, just to the left of the maf.
 

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
starts off at a decent temp & climes steadily to 90 DegC...........How it sticks at EXACTLY" 90 DegC all the time I don't know........not even varying +/- 1 DegC
Just means the thermostat is working perfectly :)
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
asthpsw wrote

So I suppose my question is :

Where are the following Enginer coolant sensors situated :
a) The one that shows up on the Climate control diagonstics
b) The one that shows on the temperature gauge on the dashboard
c) The sensor that gives the info to the ECU (which is the one on my car I'd think is faulty)



jiege01 wrote

a- dont know
b- bottom right handside of the bumper near the fog light.
c- side of the engine, followin top radiator coolant pipe back, just to the left of the maf.


jiege01, athspw wanted to know where the coolant sensors were. The one in the bumper is an air temperature sensor.

The following is for an ASV engine (TDI 110) in a Toledo. I think all the diesels in the Toledo have the same locations, petrol engines will be different.

The engine coolant system has two sensor units, one (F18) is in the radiator header tank and contains two sets of contacts that make and break at specific temperatures. In a car without aircon these control the radiator fans directly. With aircon there is an additional control unit, separate from the Climatronic and the ECU, which handles fan switching to take account of the airconditioning needs.

The second sensor unit is in the manifold that is attached to the nearside end of the head, the other end from the timing belt. This unit contains two sensors, G2 which feeds the temperature gauge and G62 which feeds the ECU. This unit is on the exhaust side of the manifold under the coolant pipework and is diffcult to see.

As far as I can tell, the Climatronic unit doesn't have its own coolant temperature sensor. It has a feed from the ECU, which must send that information if its needed.

To answer your question, a) and c) are both G62, but Climatronic gets a signal from the ECU. b) is G2.
 

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
Muttley, thanks for that concise answer, that does now explain alot & makes sense...............& explains why the Reading on the clime control is much higher than the one on the dashboard...............until the Thermostate opens.

It did make me wonder if there was a specific feed to the clime control of piped coolant water that allowed the hottest water to always be in the climate controls radiator to heat the air quicker if the climate control was infact "calling" for hot air. Bevcause I always find a bit of heat out of it rather sooner than I'd expect for a diesel.

Paul
 

J.K.jr.bad.

Guest
I had problems with this ECT, which is situated on left side of car right after coolant heating glow plugs.
My problem was such: in cold mornings (below -10C) climatcontrol won't let warm air go in even on dashboard I could see, that engine temperatur was warm engough. And it only happened if engine was totally cold - like I said in the morning. So through these inspection codes I found out, that ECT was showing - degree temperatures, and that caused climate control not to let warm coolant go through saloon heater.
After some reaserch on internet I found out, that in some time VAG was putting poor quality ECT sensors which had green plastic body. After some while they noticed this thing and corrected problem and now these sensors are with black plastic body. So I changed this sensor and problem was gone.
Only thing I would say, is don't chane it when engine is hot. As coolant is hot. ;)
 

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
So are you now saying that now you have the new sensor fitted that it does let warm/hot water into the climate control heating coils much sooner ?????..........that would be good for me as well...................because I would like to use the Air conditioning until to demist the windscreen on cold mornings........because the cooling coils actually remove the moisture from the air that is blown over the, however the VAG Climate control does not allow the Air Con to work below approx +5DegC......sham really.

Paul
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
There is no valve in the engine coolant system to divert coolant to the cabin heater. The heater matrix is always being fed with coolant from the hot side of the system - the top of the cylinder block.

The only valve in the system is the thermostat, which is in the return hose from the radiator, isolating the radiator until the engine warms up. This is purely mechanical - it isn't controlled by the ECU.

Cabin air heat is controlled by diverting air in the heating ducts. Cold air is diverted around the heater matrix and delivered straight to the cabin air vents. Heating is set by diverting some or all of the air through the heating matrix.

Air conditioning adds a cooling matrix (a refrigeration system) into the air ducts just after the air blower but before the heater and air distribution flaps, cooling the incoming air.

The refrigeration system is switched off below about 4°C outside air temp so as to avoid ice forming on the cooling matrix, which would block airflow into the cabin.

On warmer wet days the air conditioning cooler extracts water from the incoming air - cold air can hold less moisture. This drains down, and forms the puddle seen underneath the car.

OK, lets think this through

Climatronic doesn't have an independent sensor for coolant temperature, it relies on the ECU.

Climatronic needs to know coolant temperature so as to decide what to do on cold startups. Cabin demand is for warm air but there is no heat source. Climatronic keeps fan speed low and probably diverts air away from the cabin heater matrix, to let the engine warm up quicker, and perhaps to avoid the formation of condensation on the heater matrix which will make clearing the windscreen harder.

If the Climatronic sees an erroneous low coolant temparature signal it will keep the fan speed low and (I'm guessing) keep the air flowing around the heater matrix.

The dashboard gauge and ECU temperature sensors are located in the same place, next to the cylinder head, the hottest part of the system, so there should never be a big difference in readings unless one of the two sensors has gone wrong.
 

J.K.jr.bad.

Guest
I'm telling you my storie. Perhaps, you are right about controling airflow with ducts.
Regarding temperature I noticed, that in those cold days when heater didn't work in the morning (well it started work after car was left for some half and hour) engine temperature was got to working temperature a lot quicker. so probably that mean, that if you keep cimate temperature to LOW then you will heat coolant much quicker. the only issue would be not so nice weather in cabin :)
 

asthpsw

Full Member
Apr 23, 2004
524
1
Southampton
As mentioned I've a new coolant sensor & the engine runs & starts fine no problems but I wonder if anyone else thinks the following is strange.
I'm still using the Climate control diagonostics to keep an eye on things now & again.

I notice that the Dashboard Temperature gauge is getting up to 90DegC but the Clim control diagonostics still only show a much lower temp of say 45DegC which eventually gets up to 90DegC as you'd expect.
What this is telling me is that the temperature in the radiator header tank gets up to temperature far sooner that the water in the engine block......this you would expect because it is a few inches higher so the hotter water would be in there.....................BUT isn't the thermostat supposed to ensure the engine block is hot before opening up to allow water to pass through the radiator ?

Paul
 

cheshire cat

Full Member
Dec 28, 2002
1,813
1
cheshire
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As mentioned I've a new coolant sensor & the engine runs & starts fine no problems but I wonder if anyone else thinks the following is strange.
I'm still using the Climate control diagonostics to keep an eye on things now & again.

I notice that the Dashboard Temperature gauge is getting up to 90DegC but the Clim control diagonostics still only show a much lower temp of say 45DegC which eventually gets up to 90DegC as you'd expect.
What this is telling me is that the temperature in the radiator header tank gets up to temperature far sooner that the water in the engine block......this you would expect because it is a few inches higher so the hotter water would be in there.....................BUT isn't the thermostat supposed to ensure the engine block is hot before opening up to allow water to pass through the radiator ?

Paul
not thought this right thro' but on the diesel I think the stat is "at the far end" of the system and effectivly lets the cold water in rather than the hot out, also it doesn't affect the heater or oil cooler circuit:)
 

ChrisGTL

'Awesome' LCR225
Nov 17, 2007
2,459
2
Huddersfield
I'm going to replace my temperature sensor to see if I can improve my MPG.

Where is it located on the PD150 unit? Any pics ;) :)

Also, anything else I need to know before doing it? Will all the coolant come flooding out when I take my old sensor out?

Anyone got a part number?