So before I start, I know most ppl will say "milky oil = head gasket" but hear me out.

A quick history

Evo 5, Evo 8 engine.

Engine was rebuilt with oem everything) with the exception of arp head studs, amsoil oil. Also has in amsoil's oil based coolant (red).

Car's been parked for a little while. Re-did all wiring for the car but the alternator's not working.

On to the problem:

Connected the battery, started the car just to make sure the battery doesn't die.

Let it warm up completely, put car in 1st and started to move off.

Engine shut off.

Restarted it but saw a puff of white smoke.

Shut off engine, pushed car back into parking space.

Check radiator, coolant is perfect, still red.

Checked oil cap... Milky

Checked dipstick, oil is perfect, basically clear since it's still brand new.

So now am confused. A mechanic thinks the oil cap could be the problem, that it's letting in moisture thus the milky oil. What do you think?

Also I haven't started back the engine since because the battery was too weak so I've put it on a charge cycle.

My first thought was head gasket. Second, I wondered if maybe the head studs had not been torqued to spec when installed and this might have caused the head to lift but then the engine hasn't seen any pressure. But now am just confused.

 

I'd be leaning towards cracked head or headgasket, not oil cap, have you done a comp test? Id re torque the head studs and if still there lift the head for an inspection then crack test the head

 

A vehicle that is run very infrequently will get a milky oil cap as a result of condensation buildup and the engine not getting hot enough to evaporate it. If the oil in the pan isn't milky, the cap isn't milky as a result of the oil in the pan, it's condensation getting oil slung up into it.
Still safe bet to compression test etc, however to think that the head gasket failed and only compromised enough oil to affect the oil cap is a bit silly.

 

👆🏻what he said.

 

Yeah milky oil usually is water and oil mixing.

Check compression and if its low bad head gasket most likely.

If compression is well its prob condensing.