I recently replaced a leaking thermostat gasket. The thermostat was last replaced a 1-2 years ago (with aluminum housing type).
Now my radiator outlet hose will intermittently blow off the thermostat connection. The hose had not blown off since I last replaced the thermostat.
Since that gasket change, the hose will stay in place for 5-10 days, before a blow off event occurs.
At first, I was thinking that it was a connection issue - a weak retention clip etc.
But now - I'm thinking it is not likely to be a hose connection/fitment issue, because I think a bad fitment would blow off much more quickly (every day after a few minutes of driving).
I don't think I'm getting any over-pressure from engine combustion (head gasket failure). I see no sign of coolant in oil, no loss of coolant between blow offs, and - I also imagine a combustion pressure condition would not be intermittent and would cause blow off more frequently.
That leaves me with the thermostat again - is it likely/possible that the thermostat is failing in a way that it works most of the time, but intermittently gets stuck closed? And that is causing over-pressure and the blow off event?
Any other ideas of root causes I should look at?