Temperature warning

[Arctic]

You could always fit it your self just follow the link below.

https://www.the75andztclub.co.uk/for...d.php?t=216734

[Tenesmus]

Heh, yeah I saw that but I have nowhere undercover and it's too much of a faff getting the stuff off

[Tenesmus]

Well the garage fitted it, left the car running for an hour, no obvious issues, and on the way home up goes the temp gauge to 12 o'clock and the engine overheat warning comes on... I turned the heating up and down it went, fluctuating between 9 and 10 o'clock.

Got home, did the demist check and the fan ran continuously. Left it running with the aircon on cool and it continually fluctuated (quickly) between 9 and 10 o'clock. Turned the engine off and the fan kept going for a couple of minutes.

Any more ideas?

[rovertone]

Faulty coolant temp sender? False high reading would trigger cooling fan.

[SD1too]

Originally Posted by Tenesmus

Any more ideas?

Hi Pete,

You still appear to have a fault causing overheating. Has anybody drained and refilled the coolant recently? Has K-Seal been added to your engine?

Simon

[Tenesmus]

No, nothing like that has happened.

It's an interesting point from rovertone. The gauge goes up and down so fast it makes sense that the sensor is faulty.

I assume it's this one:

https://www.dmgrs.co.uk/products/oem...45-75-zr-zs-zt

At that price it's worth changing. Where is it? Nestling somewhere awkward I imagine...

How about the diagnostic trick where you display the temperature on the dash? If the numbers go up and down too fast that might point to a faulty sensor?

[vitesse]

Surprised you haven't already checked the OBD temp as that's the "real" one - here it is: https://www.the75andztclub.co.uk/for...d.php?t=308576

Yes that's the right sensor, located in one of the most inaccessible places: in the engine's V right beside the thermostat.

Regards

[Arctic]

Originally Posted by vitesse

Surprised you haven't already checked the OBD temp as that's the "real" one - here it is: https://www.the75andztclub.co.uk/for...d.php?t=308576

As Mike says above difficult to get to, in the photo below you can just about see through the manifold.

1


Here you can see with the manifolds removed marked by purple dots.
2

[SD1too]

Hi Pete,

Whilst I understand that the prospect of a cheap replacement part has its attractions, from what you've told us I doubt that the coolant temperature sensor is faulty but you might have a dirty electrical connection where the sensor lead meets the loom. You'll find it tucked underneath the rear of the throttle body. The wiring colours are pink/green and pink/black.

Here's my reasoning:

• An implausible sensor reading causes the temperature gauge to remain at full cold with the high temperature lamp illuminated (source: RAVE). You haven't reported that.
• Rapid fluctuations are not the usual symptoms of a faulty sensor. Permanently showing high resistance is common but that would lead to low gauge readings not high.
• The coolant temperature sensor is ultra reliable.

I'd be looking for an air lock or loss of pressurisation due to, for example, worn seals on the expansion tank cap. If you genuinely haven't lost a drop of coolant during these episodes then check the connector I mentioned.

As Vitesse has pointed out, you won't want to renew the sensor without incontrovertible proof. There's a lot of dismantling involved.

Simon

[Tenesmus]

I now have a thirty minute video of the diagnostic readout thingy...

I started recording when the gauge reached just about 9 o'clock and the readout said 78. The climate control was off.

At 5 minutes it says 99.

At 8 minutes it says 106 and the high speed fan starts.

At 15 minutes it says 114 (by this point I was bored and whacked the aircon on full cold to load the engine a bit).

At 16 minutes it says 116 and at that moment the gauge shifted off 9 o'clock to 9:30.

At 16 minutes and 30 seconds it says 117 and the gauge moves to 10 o'clock.

At 17m 30s it says 118 and the gauge moves near to 11 o'clock.

At 20m it says 119 and the gauge is past 11 o'clock. It's going between 118 and 119.

Now I get nervous and whack the heating up full on econ. After a minute the temperature decreases gradually.

After 28 minutes it's down to 107 and I give up.

Any thoughts?