Civic 1.5 ek3 problem

[new007]

Hi I have a petrol Civic 1.5 ek3 which has developed a fault I believe with the coolant system. Quite often when driving about the temperature gauge will go from the middle position straight down to the stone cold position very quickly and then slowly overtime back up to middle position where it repeats this process intermittently. The temperature gauge does not seem to remain constantly at the middle position like it should even on long drives. The heater warms up quickly however. It never used to do this I might add. It has effected my fuel economy and i'm getting 30-50 miles less to a tank. Any ideas on where I should start looking to fix this problem ?

Thanks

[andyiley]

Sounds like a possible air-lock in the cooling system somewhere to me.

Don't know if that engine has specific bleed points or just a cap to remove & fill the system while it "burps" the airlock out.

In general if you fill the system to the very top, turn the heater on full hot and park with the front of the car up, then run it while the temperature gets up to normal for a while that should do it.

If there are any bleed screws use them at the same time to bleed off any excess air in the system.