Gday all, My brothers EB 5.0 has dumped all its coolant into the sump ! It did nearly overheat a couple weeks before but I'm still not sure if its a head gasket or the timing cover leaking? What do you guys reckon?

more likely to be timing cover corroded through behind the water pump.

Concur with timing cover. I had the very same issue with it and the OEM one becomes porous and leaks everywhere. Discount the head gaskets with a $45 leak-down test and then go for the timing cover replacement. Water pum p would be a good thing to replace too as will the themostat. I basically removed the whole front of my motor and replaced everything from timing chain to damper. Never want to do that again in a hurry let me tell you - believe it or not the biggest PITA was the re-sealing of the sump-to-timing cover...use lots of goo and you will be good to go!!

Good luck and have lots of beverage on hand - you will need it:D

it's a big pain in the a*** and you'll have to lift the motor a bit, but i'd do new sump gasket at the same time....
you can get the felpro single piece gaskets that are really good and a helluvalot easier to fit then the 4 piece cork pieces of crap.
to do in car fitment i cut one right near the mains loop and put a dab of sealant there, otherwise it's impossible to get it around the pickup/counterweights/caps with the sump only dropped 30mm...
this was on a mates car and it's held up well (2 years ago, done canberra and back and a 1 way to gold coast, no leaks).

Thanks guys, took the water pump off, and there it was.......a pin hole! Now the fun begins!