Strange cooling system issue. Thermostat?
I've been battling with a strange issue for the past month on my 156 and I can't figure it out. I am hoping someone can help before I start throwing parts at the car and pulling the cooling system apart!
The symptoms are as follows.
1. The car warms up fairly quickly, probably in about 5 miles. It only gets to 80 degrees on the thermostat whilst the car is moving, although multiecuscan suggests that my gauge under reads by 10 degrees.
2. When stationary the temperature will climb to just over 100 degrees on the gauge, at which point the high speed fan kicks in which keeps it at about 100. It does not sit at 90.
3. When the car is warming up the top radiator hose stays more or less cold until the fan kicks in at which point it begins to warm up pretty quickly.
4. The coolant level seems to have a mind of its own. It will vanish from the header tank only to return once the car warms up.
5. When the high speed fan kicks in after warming up I get very little hot air from the vents with the heater up to full, except if I rev the engine to around 1500rpm. I then get hot air.
6. I do have some steam from the exhaust while the car warms up, but only after a long run and having let the engine cool down. I'm therefore putting it down to condensation.
I've bled the system twice now by warming the car up with the heater to full and the header cap off. The second time I did this I noticed a gargling noise behind the dash and when I ran the car at fast idle the level dropped out of the tank, a lot of air was released and then coolant overflowed from the header tank.
I then let the car cool down with the cap off, and refilled to the "min" mark on the header tank.
Now when warmed up the level in the header tank shoots way above max.
I'm pretty much lost as to what to do.
My best guess is that I have two problems.
1. An air lock - perhaps a back flush would help with this.
2. A stuck half open thermostat. Enough to just about keep the engine cool when stationary but not quite open enough for a good flow of coolant unless the engine is running at above idle as the water pump will be running faster.
If anyone can offer any help I'd be very grateful! Apologies for the lengthy post I though it would be best to be as detailed as possible.