Recently my TS has had a running temp between 1/4 - 1/3 of the gauge. Typically it would run exactly at 1/2 once it has warmed up. If I turn the car off (on acc) the temp will climb back up to 1/2 but as soon as the ignition is turned back on it will begin it's descent to 1/4-1/3. Is this kind of behaviour indicative of the thermostat needing replacing? If so, is it located at the top radiator hose?

Few other things I've done recently (if it helps) is replace air/fuel/oil filters, changed spark plugs and replaced two faulty ignition leads (others have been tested and are fine), install new ISC after the old one failed. Any help would be appreciated, cheers.

Faulty gauge?

Radiator fans running full time (thermo switch for fans stuck on)?

Nah radiator fans are working as they should it seems. I'm guessing the thermostat is stuck partially open which is keeping the car running cool. When the car's off and the coolant is sitting it warms up to the normal temp. I noticed a few drip leaks around the thermo bell housing which I've tightened up but doesn't seem to be related. Going to buy/fit the thermostat later today will report back.

They may not have a gasket but will sell a square of gasket material. Take care in marking out and cutting it. I cut the centre hole first and when I punched out the bolt holes the paper broke and I had to use gasket silicon. Next time I'll punch the holes first before cutting out the main hole. (and probably use silicon anyway.)

I would replace the temp sender

picture of the part

http://www.ebay.com.au/itm/TRIDON-Water-Temp-Sender-For-Mitsubishi-Magna-TS-EFI-TS-EFI-V6-/181695188337

I got a surprise
supercheap actually sell the V6 themo housing gasket $3.50

http://www.ebay.com.au/itm/Tridon-Thermostat-Housing-Gasket-MITSUBISHI-MAGNA-6G72-V6-MPFI-TR-TS-91-96-/221735156945?pt=LH_DefaultDomain_15&hash=item33a071fcd1

Got the thermostat from repco for $20 with a gasket. Gasket didn't have the correct bolt holes so had to cut new ones. Running temp is consistent at a touch above half way so looks like it's solved the issue. Cheers for the advice guys