Check the cabin coolant hoses at the bulkhead and the bulkhead fittings for splits. Also check the turbo hoses and lastly the pipes along the back of the engine on the bulkhead side. One last possibility is the lower coolant hose from the side/back (depending on year) to the lower side of the radiat...

Is that the dreamy 421 Silver S70 AWD?

Turbo hoses ( two of them ) or the heater hoses to bulkhead. From the position amd flow, I would guess heater hoses. Visible ftom up top

You want to be gentle removing those heater hoses. Official procedure, squeeze the yellow tabs and pull forward Crack…goes the $150 bulkhead fitting and now are under the dash for 2.5 hours of work On edit…that fitting is now $389 ouch. At least you get the $60 orings for free…. :o Gently twist the ...

The elimination option is nicely documented in the Volvo Repair Database here https://www.matthewsvolvosite.com/heater-hose-firewall-coupler-elimination-wpics/ My experience is you can use 3/4 PEX fittings if you put the fittings on the hard line, push the hose over the bulge, the sneak the PEX clam...