Replaced the thermostat on my EA as the old one was stuck open causing cold running, now with the new one fitted the guage fluctuates badly, the engine gets up to around half way on the guage then it drops right off down near the first mark, does this in cycles, up down etc. The new thermostat was the same as the old one with the valve on the bottom of it. Any ideas?

Cheers, Jeff.

sounds liek there is air trapped in the system

sounds normal to me,,mines do it since i bought it 4 years ago,,changed thermo's ,cleaned and flushed the system and it still does it.

you must remember the thermo opens and closes as the water temp changes,,if it stays the same and don't move then i'd be worried.

i once got told by a mechanic that when you first put a new thermostat in they go up and down a bit but settle after a while?

my na fairlane is doing the same i have just put a new t/stat in and it is worse.