Member Since: 08 Dec 2012
Location: SE Kent
Posts: 276
V8 - temp needle drop & can kick in
Hi all
About to embark on the Christmas getaway this afternoon and car threw a bit of an odd one. Cruising at about 45 I thought I could hear the fan coming in, looked down and the temp needle wasn’t right at the bottom but was very low - carried on until I could pull over, popped the bonnet and nothing obvious. Restarted and needle went straight to where it normally sits when warm and it’s been fine for the 10+ miles since. Coolant, oil all ok.
Anyone experienced this? Like I say due to do a 200 mile trip later today so any pearls of wisdom as to what to look for would be appreciated!
Cheers
23rd Dec 2022 10:34 am
kajtzu
Member Since: 10 Aug 2017
Location: Helsinki
Posts: 6767
So the temperature dropped while driving…?
Do you have BT IID or similar? If yes, put up the fan rpm, engine temperature and transmission oil temperature (for good measure) on the display while driving.
It could be the a sign of a faulty temperature sensor (in the thermostat housing). It could be the connector going bad. It could be the wiring.
Sensor - these do go every now and then
Connector - loosen and spray something like electrical cleaner (contact cleaner) in it.
Wiring - not much you can do besides trace and check continuity but if it is mostly ok… difficult
So all in all just keep an eye on it for now
23rd Dec 2022 10:42 am
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10732
Sounded to me as if the fan got stuck in high duty cycle mode and caused over cooling.
You shouldn’t be able to hear the fan when the gauge is at 1/4
And an ignition or engine off reset it. So do that when safe to do if it happens again
Last edited by Pete K on 23rd Dec 2022 10:54 am. Edited 1 time in total
23rd Dec 2022 10:53 am
maccers
Member Since: 08 Dec 2012
Location: SE Kent
Posts: 276
Hi thanks for the reply
Yeah, just dropped while cruising along at 45mph. I’ve probably answered my own question - I’ve plugged in my icarsoft and have code P0116 - Engine coolant temperature sensor.
Don’t want to risk it - so will try and make alternative arrangements to travel!
Thanks
23rd Dec 2022 10:53 am
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10732
Arh. So it’s detected a faulty sensor and turned the fan on as temp is unknown
I would expect the ecu light to be on
23rd Dec 2022 10:55 am
pjm-84
Member Since: 04 Oct 2016
Location: Hampshire
Posts: 2607
Yes....
Left mine ticking over for around 15min when I first had it fiddling with the IDD tool. Fan kicked in/ no reading on temp gauge. Did a quick drive and horrible. Stopped and restarted and all fine / temp reading again.
Changed 3 sensors associated with the temp gauge / circuit ( 1 up top / two down by the oil filter?) and never had any issue again. Changing the temp sensor up top may be the first port of call. Very easy and accessible.
23rd Dec 2022 10:57 am
maccers
Member Since: 08 Dec 2012
Location: SE Kent
Posts: 276
Did find it a bit strange - no lights, no bongs, temp needle just sitting low and viscous fan roaring away. Recycled ignition key and was back to normal straight away
23rd Dec 2022 10:57 am
pjm-84
Member Since: 04 Oct 2016
Location: Hampshire
Posts: 2607
10min job for the top sensor. Did the other ones in with an oil change so they were in the tool box for a while.
23rd Dec 2022 11:00 am
maccers
Member Since: 08 Dec 2012
Location: SE Kent
Posts: 276
I’ve been sitting here for 10 mins watching the temp and it’s behaving - but not sure the wife would be so confident going on a long journey!
Could be one for when we get back
23rd Dec 2022 11:03 am
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10732
Buy a sensor off shelf and take it with you ?
23rd Dec 2022 11:26 am
maccers
Member Since: 08 Dec 2012
Location: SE Kent
Posts: 276
Unfortunately can’t find a part locally in time for us to leave
23rd Dec 2022 12:07 pm
Yankee_Rover
Member Since: 02 Jun 2021
Location: Seattle
Posts: 183
It takes two drive cycles for a faulty temp sensor to set a CEL. I’m assuming the P0116 you pulled was a “pending” code which means it was set after the first drive cycle and is stored in ECU short memory. If after 3 drive cycles it is not triggered again the pending code is erased. This is standard OBD II logic.
This is just to explain why you had no CEL. If you experienced the same problem within 3 starts and hadn’t cleared the code, you would have gotten a CEL.2008 LR3 HSE, 4.4L V8
23rd Dec 2022 1:22 pm
Lrstaylor
Member Since: 03 Oct 2018
Location: Kent
Posts: 619
It's your thermostat stuck open I had exactly the same on my 4.2 sport, better stuck open than stuck shut.
There a x3 part stat you have to assemble.
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