Guys, my 012 L322 4.4 diesel is running fine, but during the last few days, if running with the air con on in traffic, the temp gauge is creeping up to the 1pm position… I noticed it by chance, as I thought I heard the fan roaring… well, it was roaring even when pulling forward a tad… so if I then switch everything to full hot on the heater, it immediately drops to the 12 o clock position, and remains there… I suffer inside, so carry on with windows down. No coolant issues I know of, checked and bled a couple times.. ,I’m linking it to fan-roar even when moving briskly.. with heater running in hot position. no codes on my gap tool either.
Do I have a secondary electric water pump, which might be lazy?… my main water pump was changed last year. Shall I get a new thermostat? If I check the coolant temp with heater on, it’s about 100 degrees, didn’t check it at 1pm position. Car driving fine, but noticeable roaring of fan. Any pointers please. Thanks.

I'd suspect the thermostat but check for parts availability before you tackle it as there was a serious shortage earlier in the year ( mine failed open). You can't buy just the thermostat either an you need the whole coolant mixer box but you can just then swop out the thermostat and housing (3 and 4) to avoid removing the whole box.

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I did find just a thermostat available on eBay…. Did you swap out just the stat, or did you replace the whole unit… can you remove the old one from the housing?

this might be a generic picture… https://www.ebay.co.uk/itm/314560941094?mk...media=COPY

Had to replace the whole lot but then found out it's possible to just replace the housing and thermostat although the screws were very tight.

Click image to enlarge

What were your symptoms to necessitate the change please…. I’m sitting here trying to reproduce the fault… I’m getting fan roar at idle and when driving with AC on but fan goes ‘off’ when heater put on and AC obviously off. Car idles higher with AC on etc.

Mine was the opposite - slow warmup in winter and temps dropping when moving faster / more rad airflow. As on the pic the thermostat seal had failed and was leaking coolant 2012 TDV8 Vogue (L322)

johnboyairey wrote:

What were your symptoms to necessitate the change please…. I’m sitting here trying to reproduce the fault… I’m getting fan roar at idle and when driving with AC on but fan goes ‘off’ when heater put on and AC obviously off. Car idles higher with AC on etc.