Catastrophic radiator failure (upper hose connection to “exploded” plastic radiator fitting). @118k odo miles going 70mph on freeway and driving for 2 miles to next exit after warning lights. This has no doubt caused extreme engine temps. There is now white smoke blowing out the exhaust after installing a new BEHR radiator, thermostat and hoses. Engine cold but noted lots of combustion gas pressure in the coolant expansion tank. Frothy looking oil on underside on oil fill cap. Also see some oil weeping out the rear cam position sensor (inner cam seal blown?) Engine has only run less than 10 minutes in park after the radiator job and turned off after noting the white tailpipe smoke.

Need some guidance on what’s next…
Just invested $900 replacing front suspension parts and replacing the radiator but S90 is in otherwise relatively good shape. The mobile mechanic who replaced the radiator suggested running a head gasket sealing solution (Blue Devil) after flushing the coolant. I think this is waste of time and money and could cause more damage. Any positive experiences using any head gasket sealants? Aren’t they just “snake oil” and a temporary fix at best?

What are the chances for a successful repair if the head is not cracked but only a blown gasket? Should valve stems guides spring also be replaced? What can I expect to pay for this head gasket repair job?

What if the Al. head has cracked.... could it be welded successfully? If not, what will a new head cost and the labor to salvage parts from the cracked head and instlal to the newe head? Is this even cost effective?

Could pistons and/or crankshaft also be compromised by antifreeze in the combustion chamber?

I'm considering just going for a remanf. engine instead of pulling the head to asses the actual damage? Where can I find one. Would labor hours to remove/replace engine be less than labor to do the head job?

Appreciate any advice or comments.