MrAl wrote:...Mine does not have an expansion cap.
What do you think you have on top of expansion tank?!Expansion tank cap.Grey or green one.
Let me say it like this...when you change your coolant and when you start the car to bleed the air from system untill cooling fans kicks in....coolant doesn't escape from expansion tank...except you overfill it.
Of course that there is some pressure in the system but that is something minimal.
That does not look like an expansion cap, but then i have not examined it in detail which i will do next time.
But if it is an expansion cap, where does the liquid or steam come out if the pressure gets too high? I dont see any holes in it but i will look closer.
Saying that the pressure is minimal does not tell us anything though as we need to know what it really is, 1 psi, 2 psi, 3psi, etc., and i think it is around 14.7 psi or a little more like Steve suggested. That means it will spew out if the cap is opened. If you have ever opened a more standard radiator cap you know it will spew out, so that means there is pressure, and that means that fluid would come out if it was not sealed. If it is an expansion cap then it does not normally leak anyway right? That's unless it is defective, which i guess is a possibility.
So i guess what you are saying is that if the pressure goes too high it will somehow come out the 'expansion' cap. That's fine, but the cap on mine does not look like an expansion cap so where exactly does the fluid come out of that cap if the pressure gets too high?
But even up to that point the system would be considered sealed, albeit conditionally, otherwise coolant would escape all the time when hot.
I’ve been driving a Volvo long before anyone ever paid me to drive one.
1998 v70 on the road since April 2nd, 2015