Can anyone help with temp gauge problem

Hiya, does anyone have any thoughts on the problem I have with my Freelander. Whilst driving the temperature gauge will suddenly swing over to max. If I turn the engine off for 20 seconds and back on then the gauge reads midway as expected and is fine for a while until it does it again. Just before it happens the temp gauge needle often twitches a bit. The car seems to be running normal with no obvious crossover of oil/coolant. I have changed the temp sensor which didnt help. It may be my imagination but it does seem to happen more on warm days.
Can anyone help? I did pop into LR dealer who said head gasket but wondered if there is anything it could be before i go down that road, especially as it is running well. Thanks

wot motor is it ?

Yes sorry it is 1.8 petrol 2005

Could be exhaust gasses getting into the coolant causing airlocks, mine did exactly the same thing. If so then like mine it's a headgasket job - luckily though it's early stages of HGF and there might not be mess with mayo everywhere etc. But sure does sound like the begginging of HGF to me. Best keep it off the road until you know for sure or you may end up with full blown messy HGF.

Will.

or could be a faulty sender unit get a leak test done

Had this one before....kind of.
Started with engine MIL light coming on and off randomly before progressing to wild swings of the water temperature gauge. Turned out to be a weak battery in my case. Having said that, my vehicle is a TD4.

What do the fans do? Do they come on and go nuts to cool off the engine? Mine did so just wondering .

Will.

Block test it. Will tell you if you have hydrocarbons in your coolant.


Could also be simple as sticky thermostat, crappy waterpump or gremlins.

Thanks folks, yes the fans go mad trying to cool what they think is an overheating engine. Guess I need to take it in and see what they say. Thanks for the advice

Have you tried bleeding from the heater hose after a temp spike? If a ton of steam hisses and spits out no matter how many times you bleed it then that would be a strong indicator of a head problem.

Let us know how it goes .

I would expect this to be an elecrtickery fault and unlikely to be related to actual engine temp, since it flicks over to max and then back to normal after 20 seconds (of being turned off).
Would it be worth checking how hot the heater is compared to normal?
IMHO I would first check for a damaged cable,damaged temp sender unit.