Join Date: Apr 2016
Location: Central Coast NSW
Thermostat change should just work... i own a golf gti 1990, 16v, and those are notorious for air locks.
Whenever a thermostat is in question, i feel the temps of the bottom hose to start.
Then you might have the option of peeking into the collant temp port, but I think it easier to remove it completely.
When i changed the one on the jts 2004 2.0 16v, it was calcified due to tap water and electolysis caused by the collant temo. So be sure to finish this job withndeminerlaised water.
I also flushed the heater matrix out with a hose fitting and flushed theough the block via the collant reservoir. All indicators seem that your thermostat is stuck shut, if you remove it qnd placemit in a pot of boiling water you might get some results. Also from my experience with the golf, the fan thermo switch on it is on the rad, not sure where the one os on the alfa. But my old radiator had seen better days and when I replaced it, the fans behaved more like they should have. I guess there wasnt enoigh flow pasg the thermoswitch that triggered the fans.
The thermostat in the alfa originally had a rail, the afte market was a plane jane mounted in a housing. The original with the rail was subject to the calcification and im happier with the after market. In would get the thernostat back off, pain I know and check there isnt something stuck inside preventing it opening, then check and replace if it doesnt open in the pot test
Dont keeep overheating the engine either, bad things happen as the prssure inceeases