I am looking to replace the engine of my VOLVO V50 and I was wondering if the engine from other cars (such as peugeot, ford or citroen) is compatible or my car or it HAS TO BE from another Volvo

 

I think you can fix that with a quart of Marvel's Mystery Oil... ;-)

Seriously, unless you're trying to do something really "unusual", don't even THINK about crossing platforms with the replacement engine. It's simple to get 90% of the install done, but that last 10% - sorting out the bugs, chasing the right modules and working out custom interfaces, is going to take you forever.

Just find the same engine from an S40 or another V50, and call it a day.

And please, let us know what caused your old engine to grenade like that...