Originally Posted by drewactual

I've got my flak jacket and helmet ready for the impending incoming firestorm this is about to cause- but:

if an engine is 250+ degrees, and it's NOT blowing steam and/oil screaming, sometimes it's better to let it run- to keep the water moving and to keep oil from coking on hard parts.......

a water hose spraying through the radiator on a cooling system that is maintaining pressure (not boiling or flash steaming) will knock thirty to fifty degrees off the engine in a heartbeat. oil can handle the heat- most quality oils can handle several cycles of 250 before they start to degrade- most won't flash (or burn minus required o2 which is 'coking' and which leaves that wicked hard 'cajun crust' on hard parts) until nearing 400*....

that engine will get MUCH hotter as soon as it stops running and circulating oil and water. the coolant/water WILL flash (poof) like a steam machine if the cooling system isn't close and under pressure... the oil becomes stagnant and thickens on surfaces 250+*....

IF IF IF the cooling system is intact, spray water on the radiator for a few and then ****** the cap off and stick it in... the threat of hydra-locking isn't massive until you try to start it again after such a failure... IF the engine doesn't have bearings screaming this is an option.... as soon as it is under control- control being 220ish, THEN shut her down......

watch a nascar race (requires heavy drinking) and watch a delay... they'll stop the cars on the track and roll a cart out to them... that cart has everything needed to keep both oil and water circulating while they sit... after you turn off that key, THIS is when warping happens and shifting of mated surfaces occurs while metal expands/contracts at a different rates, causing gaskets to blow (other than cylinder pressure and catastrophic failure, this is when most head gaskets and/or water pump gaskets are compromised- during the 'sitting- first super heating and then slowly cooling phase)

Originally Posted by RubenZ

Makes sense. Hens the Reason why you when you shut the engine off real quick to run into a store and come back out the temps are a little higher until you get coolant flowing again.