Volvo S60 Kühlmittelstand | Posts 16+

Quote:

Maybe the pressure relief valve in the coolant cap is broken? Put a new lid on it,

That would mean that the pressure relief valve is not opening, or is opening too late.

If a closed system with an expansion tank has a properly functioning valve that opens, you will inevitably have a problem with the coolant pressure.

Hi!
Let me think.
The lid (at least in some models) has two valves in it.
I haven't really explored the functionality yet.
There's a valve that allows air to enter when a certain vacuum pressure is reached, as the engine cools down.
Then there's another valve that releases the air that has been drawn in, at a predetermined overpressure, when the engine gets warm.

If the exhaust valve is not working, but the intake valve is functioning.
The effect described here could potentially occur.

I think so, at least.

Otherwise, when there are problems with the cylinder head gasket, it's usually described as if it's erupting like a geyser or spurting out from the water reservoir when the engine is hot.
when the CO₂ dissolved in the coolant reverts to gas bubbles due to the pressure loss. This only happens as long as the coolant is below 100°C.
I feel like that's missing from the description.

What I also noticed is that the radiator hose that runs from the thermostat to the upper radiator connection is completely cold.

chriskross wrote:

What I also noticed is that the coolant hose, which runs from the thermostat to the upper radiator connection, is completely cold.

Hi!
Well, there it is.
Either the thermostat isn't opening properly, or it hasn't been bled correctly. As I suspected.

Check if there's a bleeder valve at the top of the radiator, or if necessary, disconnect the upper radiator hose.
Then, fill it with coolant until it's full.

You can easily detach the hose so that only a small opening remains at the top, and then fill it with a small container of coolant.

Good news: since the thermostat was replaced, everything is working properly again.

Coolant level remains constant again.

That sounds good, and thank you for the feedback .