Hi all, my first post on here so please be gentle!

Recently bought a Td4 2007 Fl2, and all is well but I noticed that when stopped at junctions the temperature gauge would drop to the “start of normal range” position until I pulled away. IID did show it was sitting at about 72-75deg so that was consistent. So I swapped out the thermostat housing and now the needle sits in the centre as it should and the IID reads hotter.

The thing is, I’ve tested the thermostat I took out and to my surprise it isn’t stuck open. In fact it seems to be working just fine. So I was wondering whether the dodgy gauge readings might be because the temperature sender on the old housing is duff.

Does anybody know what the resistance/temperature curve of the sensor is supposed to be? If I can confirm the sensor is duff then I won’t junk the old thermostat and will put it in my (growing) pile of Stuff That Might Come In Handy Some Day!

Thanks,

Chris

Confirm the temperature is now higher using a diagnostic unit. Although the higher reading on the gauge supports this.
If the CTS goes out of specs by a large margin, the ECM will flag a fault. 2009 Rimini Red SE TD4. Soon to be sold.
Hyundai Ionic 5 Ultimate on order.
Gone. 2006 Tonga Green i6 HSE.

@Scarecrow, you said the IID was now reading hotter but did not post the new numbers. What are the new numbers? Are you certain your rad fan is engaging? Can you see/hear it running?

I consistently run at 88-89C but it can go upto the mid 90s at times. Tranny temps are usually 8-10C lower consistently.

As per your question, see below...

MotionInc wrote:

@Scarecrow, you said the IID was now reading hotter but did not post the new numbers. What are the new numbers? Are you certain your rad fan is engaging? Can you see/hear it running?

I consistently run at 88-89C but it can go upto the mid 90s at times. Tranny temps are usually 8-10C lower consistently.

Hi Merlin, mine is the 2008 si6 as well .
Just hover your cursor over the tambora flame icon just below my avatar pic.

Hello all and thanks for all the replies! To deal with various questions:

Yes I have confirmed it’s now reading higher with the diagnostics. I went out for a short run and it climbed into the 80s (I forget the peak, was just happy to see the 8 come up). I need to do a long run and leave it running to log the data but haven’t done so yet.

Many thanks to Alex for the table, that’s exactly what I was looking for! I’ll dig out the multimeter and go take some readings

Thermometer has gone AWOL somewhere in the workshop which has curtailed things a little. So the only two readings I have any confidence in are ambient (about 15C I think) which is reading 3800, and a mug of water poured from the kettle a few minutes ago (so probably 90-95C?) which reads a touch over 500. These look a shade lower than I expected but I need to find the thermometer to get some decent points on the graph. However it’s certainly following the correct inverse temperature coefficient profile so not totally bust.

I guess a bad connection might have been to blame. I couldn’t get my hand in to pull the plug off until I’d wiggled the housing out a bit so hadn’t tried the usual unplug/wd40/reconnect route. If there was some crud on the connector it would have increased resistance and given an artificially low reading on the IID. Might have been able to save the cost of a new thermostat!

If I can find the thermometer I’ll post some proper figures. Thanks again all, especially Alex for finding the exact answer