Oil / Coolant Leaking and Mixing. Low pressure. No CEL. Intake Manifold Gasget?? - '09 Chevy Malibu

Question

Alright guys, the Malibu is back!

Issue: Wife was driving. Oil pressure light came on. Pulled over. Car wouldn't start for next 10 minutes. Then started right up, and made it home (Light was gone).

Symptoms:

Oil: Yellow fluid in oil cap. Oil appears normal on distick. Oil NOT low. It appears to be above full. New. Was fine in Nov at last oil change.

Coolant: Super milky tank. Near-solid clumps of grey goo. Been like this for a while. Also, tank was EMPTY a month ago and refilled. Looks low again.

Clicking: Wife ways theres a clicking noise. Described at similar to a fan blade hitting the housing and clicking as it rotates. I haven't heard it.

Non-symptoms:

No oil or coolant pooling under the car. No CEL. No low oil.

Theories

Primary: Intake gasket leak. Would explain the oil / coolant mixing.

Secondary: Head Gasket leak. Same as above, but harder to fix myself.

Any other possibilities? Also, and recomendations on how to confirm, before I waste time replacing parts?

Updates

Took the cover off. It’s pushed oil back up thru the carburetor into the air filter. Does the indicate any diagnosis in particular?

Took the intake manifold off / back on. No sign of leak or issue there.

Drained radiator fluid / oil. Replaced both. The oil didn’t actually look that bad. Should it be very milky if it’s a blown head gasket?

Also, won’t start at all now.

Answer 1

Theories are correct. You have a small coolant leak into the engine, could be a head gasket or other gasket that allows coolant to lean into the engine oil area. Its hard to diagnose but can be done.

Preferably done with a hot engine (some coolant leaks only occur with a hot engine): Drain oil and leave plug Out, pull all spark plugs, next connect a radiator pump and pressurize the cooling system to 15 psi, let sit for an hour (monitor pressure and keep at 15psi for the hour), see if any coolant drips from the oil plug during this hour, if not after an hour spin the motor over and see if it pushes coolant out of any spark plug hole (hold a paper towel in front of the spark plug hole, this helps show small amounts of coolant you might miss visually). If no signs let it set pressurized overnight with a clean drain pan under the oil plug hole.

This narrows down the possibilities, either a head gasket, or cracked cylinder head (spark plug hole spits coolant) or other gasket which is most likely intake.