Avensis 1999 Problem With Water Temp Guage Reading

[nighthawke]

Hi

Can any body help, i have a avensis, and during the cold weather i have noticed, that firstly it takes a long time to warm up.Once i am driving and the water temp guage in the car is in the middle where it should be, the temp quickly goes down the faster i drive,if i stop for long it goes back up.I suspect this is the thermostat since the car does not go over the half mark at all.Would it be possible i am close to the solution.I have had the car 8 years no problems.all water topped up.Can any body tell me where is the thermostat on a 1.8 gs 1999 pertrol engine.Is there a procdure i can check , to make sure the cause is certain, to a solution, example new thermostat/

please help

nighthawke

you can also e mail me on skyhawk7862000@yahoo.com