Coolant recovery tank question

[subzerocarfanatic]

I noticed yesterday when arriving back home after a short 20 minute drive that the coolant reservoir tank was filling all the way up just about with boiling blue coolant.
It was way past the max fill line, when the car sits before being started and warmed up it is actually on the min level line, maybe a hair below. As I sat there watching it i could hear it gurgling or boiling in the hose and reservoir tank,it was coming out of the tank going in to the small over flow hose that leads back to radiator hose, I know this is a process,but is this normal for the C70 5 Cylinder Turbo? I ran the A/C while driving and the coolant fan was on while running the A/C. After i got home I turned off the A/C and the radiator coolant fan ran for maybe 10 seconds after the A/C was shut off then it cut off.
I have not driven the car for more than 15-30 minutes at a time since I have been working on it then taking for a short run but I can't recall the coolant fan coming on unless the A/C is on.I just replaced the ECT with an OEM Volvo one like suggested so I know it is good,could I have a bad fan relay or what? The car never seems to run hot according to the temp gauge anyway,it never gets above the half way mark on the temperature gauge. Any ideas, am I worrying for nothing?
I wanted to add this, when I ran the DICE scan tool last I was able to activate the radiator coolant fan with the VIDA DICE.

[Clemens]

I'd say yes. Both of my T5s do that. The R does it more, the regular T5 does it less. In a german forumbthere was a lenghty discussion on this topic a while ago and the concensus was that because of the design of the coolant system the fluctuation betwen cold and hot is quite high and even if cold the level must not necessarily be the same every time. It makes no sense, but both of mine have been running great for years that way.

[FLXC90]

Once the motor is off, the pump stops circulating the coolant. Thermosiphoning will normally occur after that, when heated coolant moves to the recovery tank and back to the system. figure the recently-cooled-through-the-radiator coolant remaining in the hot engine passages is still expanding until temperature equilibrium is reached, then the process will end. Until then it creates its own pressure, and pumps through to the recovery tank (and out the little hose)

[MoVolvos]

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There is a difference between a Recovery tank and Expansion tank. The Recovery tank is not under pressure and is there to "HOLD" coolant that is let off by the Radiator Cap when the engine gets too hot.

The Expansion tank is part of the cooling system under pressure. In terms of level it should be at the Max or between the Max & Min in the morning. Regardless when you check it as long as the fluid level remains the same in the morning the system should be fine, meaning you have no coolant loss.

On our 03 S80 T6 the coolant actually goes lower when it is hot rather than higher which to me is unusual but it is consistent. When it is cold it sits at the Max mark. The lower radiator blew off recently and then we had to repair the leak at overflow hose in the Expansion tank. We've been checking everyday going on two weeks and there have been no coolant loss.

Don't worry about the level at any given time rather check the level for coolant loss when it's cold and not under pressure in the morning. If it remains the same you should be fine. If in doubt get a pressure test or hydrocarbon test.

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