Volvo Engine Cooling System

[kspirit53]

I had a similar problem on my 2020 which was quite simply the screw down lid to the raw water filter not having been tightened down tightly enough to make an air tight seal. Air was consequently being drawn into the system which seems to explain your problem. Could be worth a try given the problem has only occured since the service and you sound confident that the new impellor is good.

[LeonF]

Do they all have the seal ?? I don't remember having one, and it works fine, but I do have a speedseal.