Coolant temperature erratic

MikeT · Unread post by **MikeT** » 26 Apr 2010, 14:22

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?

Unread post by **KennyW** » 26 Apr 2010, 15:02

Hi Mike,

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

Kenny

MikeT · Unread post by **MikeT** » 26 Apr 2010, 15:47

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.

Unread post by **KennyW** » 26 Apr 2010, 16:50

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.

Kenny

MikeT · Unread post by **MikeT** » 26 Apr 2010, 17:40

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

) 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.

Unread post by **KennyW** » 26 Apr 2010, 18:07

Thanks Mike,

Where is the gauge sensor located

Kenny

MikeT · Unread post by **MikeT** » 26 Apr 2010, 19:23

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

Unread post by **CitroJim** » 26 Apr 2010, 19:35

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!!!"

MikeT · Unread post by **MikeT** » 26 Apr 2010, 20:04

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

Unread post by **CitroJim** » 26 Apr 2010, 20:37

Lexia rules

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

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...

admiral51 · Unread post by **admiral51** » 26 Apr 2010, 21:03

Do These help

Colin

red_dwarfers · Unread post by **red_dwarfers** » 26 Apr 2010, 21:13

On mine the one at the back is a green one

MikeT · Unread post by **MikeT** » 26 Apr 2010, 21:14

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

And it failed to develop?

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

Thanks Colin and Jim!

Unread post by **KennyW** » 27 Apr 2010, 09:47

Thanks Jim and Mike,

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

Kenny

MikeT · Unread post by **MikeT** » 27 Apr 2010, 14:01

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.