Magnum cylinder head crack
Ok, so it's not into the water jacket, it's a blind hole for the exhaust manifold that is cracked through to the exhaust port...
Threads are not perfectly sealed and some air/water can pass between the threads and leak... That may have also been making an exhaust leak noise...
Since exhaust gasses are not good to breathe and long exposure can kill you, I would recommend using high temp thread sealant to keep any exhaust gasses from passing through the threads into the engine compartment and possibly into the cowl and get sucked into the HVAC and circulated into the interior... Especially when it is cold and you are using the heat, the HVAC gets it's air supply from the cowl... Any exhaust that leaks from the engine compartment can enter the HVAC through the cowl...
I would recommend using a high temp thread sealant to keep exhaust gasses from leaking into the engine compartment and possibly into the interior and causing carbon monoxide poisoning... We're talking life and death, don't take any chances...
You need something that can handle high temp from the exhaust... I did do a google search and found a couple of sealers that are rated up to 1800°F, this first one is 2000°F and affordable...
Here's a link and it's not too expensive:
https://www.amazon.com/Vibra-TITE-1...ocker-Translucent/dp/B07XW2ZTZL?tag=fabo03-20
Then there is this Deacon 8875-Thin thread sealer... It doesn't list a price but is rated to 1800°F... You need a thread sealer, not a thread lubricant like some of the other products they offer... This is the one I would use if I chose this one...
Here's the link for that one:
https://www.jetlube.com/product/deacon-8875-thin-thermal-reactive-paste-sealing-compound
Permatex makes a hi-temp sealant, but it is only rated to 400° F... I included this to show you an example of what not to buy for this...
No good for exhaust temps...
Spend the money to seal it correctly, it's not worth the risk to you and your family...
Ok, so it's not into the water jacket, it's a blind hole for the exhaust manifold that is cracked through to the exhaust port...
Threads are not perfectly sealed and some air/water can pass between the threads and leak... That may have also been making an exhaust leak noise...
Since exhaust gasses are not good to breathe and long exposure can kill you, I would recommend using high temp thread sealant to keep any exhaust gasses from passing through the threads into the engine compartment and possibly into the cowl and get sucked into the HVAC and circulated into the interior... Especially when it is cold and you are using the heat, the HVAC gets it's air supply from the cowl... Any exhaust that leaks from the engine compartment can enter the HVAC through the cowl...
I would recommend using a high temp thread sealant to keep exhaust gasses from leaking into the engine compartment and possibly into the interior and causing carbon monoxide poisoning... We're talking life and death, don't take any chances...
You need something that can handle high temp from the exhaust... I did do a google search and found a couple of sealers that are rated up to 1800°F, this first one is 2000°F and affordable...
Here's a link and it's not too expensive:
https://www.amazon.com/Vibra-TITE-1...ocker-Translucent/dp/B07XW2ZTZL?tag=fabo03-20
Then there is this Deacon 8875-Thin thread sealer... It doesn't list a price but is rated to 1800°F... You need a thread sealer, not a thread lubricant like some of the other products they offer... This is the one I would use if I chose this one...
Here's the link for that one:
https://www.jetlube.com/product/deacon-8875-thin-thermal-reactive-paste-sealing-compound
Permatex makes a hi-temp sealant, but it is only rated to 400° F... I included this to show you an example of what not to buy for this...
No good for exhaust temps...
Spend the money to seal it correctly, it's not worth the risk to you and your family...