Coolant temperature erratic

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MikeT
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Coolant temperature erratic

Post by MikeT »

Thanks to the Lexia, I've noticed the ECT sensor is reporting erratic temperatures, showing a huge range from as low as -34 to +145 when I guess the true temperature was about 20-90 as it warmed up on idle.

I think I made it worse by wiggling the wires close to the connector but is it usual (within the ECT sender spec) to show such a wide range of temperatures - given such conditions or does it point to a more serious problem like failing ECU?
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Post by KennyW »

Hi Mike,

Could it be the sensor on the fuel filter housing/thermostat not earthing correctly.

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Post by MikeT »

Hi Kenny, possibly and I can test that theory when I'm working on the car next. What puzzles me is the reported range going both high and low.
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Post by KennyW »

Hi Mike,

I have a problem with mine which is. The temp gauge does not work for long periods especially during the winter but as spring arrives it suddenly works for a short time then stops even during a short journey.

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Post by MikeT »

Hi Kenny,

The engine coolant temperature sender and the dash gauge sender are individual parts - Green = dash gauge, Brown = Bitron and Blue = ECT.

I've just been out for a quick looksee and I'm 99.9% sure it's the sender itself as with it disconnected, the Lexia shows a constant -45 (In hindsight, I should have checked to see if it logged a fault code too :oops: ) and with my multimeter hooked up to the sender, it read correctly until it got warm/hot then all hell broke loose - readings all over the shop, hence my certainty the sender is fubar'd.
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Post by KennyW »

Thanks Mike,

Where is the gauge sensor located :?:

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Post by MikeT »

On mine, they're all on the thermostat housing which is under the fuel filter.
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Post by CitroJim »

That'll be affecting your timing Mike as the engine ECU uses the ECT temperature to determine things..

Strange it's the blue sensor on Diesels. On petrols the ECT sensor is always the green one.

French logic is bizarre at times... "Oui Jacques, the ECT is Bleu and therefore a diesel!!!"
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Post by MikeT »

CitroJim wrote:That'll be affecting your timing Mike as the engine ECU uses the ECT temperature to determine things..

Strange it's the blue sensor on Diesels. On petrols the ECT sensor is always the green one.
Yes Jim, was interesting to watch the live parameters, it's the timing that drew my attention to the temperature as it happens. I was watching it slowly retard as the engine warmed up then it suddenly raised to 7 or more degrees and the subsequent knocking had me concerned. When I saw the coolant changing from 70's, 60's, 10's, 70's, 50's etc I saw the connection. Great things these tools!

I might be sort of colour blind when it comes to some shades of green and blue - so, let's just say my ECT is the one at the back :lol:
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Post by CitroJim »

Lexia rules :D Bloody handy aren't they Mike! Without one you'd have never spotted that...
MikeT wrote: I might be sort of colour blind when it comes to some shades of green and blue - so, let's just say my ECT is the one at the back :lol:
Ahh, now if memory serves me correctly and it's been a while since I had a 1.9TD now but I fancy the one at the back is a green one.

My memory might be the dodgy party here though...
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Post by admiral51 »

Do These help :)

Image

Image

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Post by red_dwarfers »

On mine the one at the back is a green one :)
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Post by MikeT »

Did I also mention my photographic memory was only loaded with black and white film? :oops:

And it failed to develop?

Sorry Kenny, it's the blue one you want for the dash gauge.

Thanks Colin and Jim!
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Post by KennyW »

Thanks Jim and Mike,

If that sensor is faulty would that explain my running issues.

Kenny
C5 x7 2.0 HDi 160 hp Estate exclusive, the newbie
Xantia 2.0 Hdi 90hp 1999 only 189,000 and rising!!!!!!! Moved on to a new home
C3 1.4 petrol (SWMBO)
Xantia TD 1.9 Mk 2 Estate LX 1998 model over 210,000 miles now and still rising!!!!!!!!!!!!! now deceased 17/12/2010.
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Post by MikeT »

The dash gauge sensor (blue) has no part in engine management. It is purely for the driver's information.

If your Bosch pump has full timing control (as mine does), the green (rear) sensor is the one to check.

To test any of them; Connect a multimeter to the sensor pins, set the scale to resistance and run the engine. As the coolant warms, the resistance changes (drops I think). Check the change for smooth progression.

Mine starts off normal but goes haywire after a while.
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