Mitsubishi Montero head gasket: Is it normally a head gasket or are these known to have cracked blocks or heads?

coolant filling the engine oil? I would suspect a head gasket or piston liner gasket failure, I this is happening when you fill radiator and engine is still off I would look at the block itself for a crack in the piston wall(internal damage), if this is while running consider the head gaskets

does the engine run smoothly or do you detect a slight miss in it..if air is getting in to the cooling system its normally a blown head gasket..or cracked housing somewhere..

Blocks rarely crack, heads do crack more often. Most likely you have blown a gasket. Unless you can see coolant coming from a crack , you will have to disassemble it to find out

To start check the oil and see if it is milky looking on the dipstick if so you have likely crack the head or blown a head gasket and possibly warped some valves witch would keep it from starting.

if you are so sure, go replace the head gasket! its not costly!

if it continues to do this while you drive, it is a sign of water/coolant in the exhaust due to a cracked head, block or most likely headgasket going out. Deal with this immediately before you need a whole new motor...

Typically would not overheat until enough coolant was lost. Find out if they mag fluxed the heads, or had it done. A lot of shops rebuild without doing this step as it's expensive. If they got a rebuilt head, again they need to know if it was mag-fluxed.
It's harder to mag flux the block while in the vehicle and assembled.

you either have a cracked block or the head job they did is not good. It is very easy to screw up a head job. Also they may not have put in the right gasket. If they had to shave a lot of the head off, then you need a thicker gasket. If they used the standard head gasket will break or leak again.

Known issues or not,It sounds like the head gasket is blown,or it has a cracked head.If it was water it would be thick and light grey in color on the dip stick,But yellow indicates antifreeze leak that has not had time to mix with the oil.

1 Inspect Piston Ring Set Worn or broken piston rings. 2 Inspect Valve Stem Seal Cracked or brittle valve stem seals allowing oil to enter combustion chamber. 3 Inspect Head Gasket - Performance Head gasket leaking coolant into cylinders 4 Inspect Fuel Injector Rich injector 5 Inspect PCV Valve Plugged or damaged pcv valve. 6 Inspect Engine Worn or scored cylinder block 7 Inspect Piston Worn or damaged piston. 8 Inspect Valve Guide Worn valve guides