BlueDevil head gasket sealer...2004 Cadillac Deville

You should also have a cap on the radiator throat (top of radiator). After doing the flush to clean out the system, pouring the BlueDevil in the radiator is the direct way to seal a leak like this from the inside. It actually works pretty well on moderate leaks but is not permanent. Removing the thermostat in this process is important to keep the cooling system flowing. After the fix is complete don't forget to reinstall the thermostat in the correct direction.

2000 to 2005 Cadillac Deville has no cap for the radiator it is sealed. it only has a reservoir.. you should know your facts before you answer.

I know it is a little late, but take the top hose off going into the engine and hold it up and poor it in there. This hose goes to the top of the radiator.Then put back on and do what else it says to do.

I want to know how your mechanic came up with a cracked head without removing and disassembling the engine. I wouldn't use any of those off the shelf head gasket sealers in a bottle for any car let alone a Cadillac. That stuff causes more problems then what you had to begin with. Its not good for any technologically advanced engines.

For a “technologically advanced engine” they sure could have used a better method then the direct injection system and while I am at it, changing a blinker bulb in the front seems to be a job for a Dr not a mechanic.... SRX is the worst thing Cadillac has made.

So did it work?

Probably the typical Northstar head bolt failure.