DML FAQ : Engine : I seem to have lost a lot of oil, but can't find it. Where to start?

I seem to have lost a lot of oil, but can't find it. Where to start?

From my experience, it's possible to lose that much oil from a badly, blown belly pan gasket. I lost quite a bit (kept bringing it back it) from a partial (and I do mean partial), leaky belly pan gasket before it sealed itself back up.

I would check the following (many have been already mentioned):

  1. Check the inside of your exhaust pipe/tip (once it's cooled down, naturally). I would just use my finger and see if it's oily or how oily it is. If quite oily, then it's probably coming through the exhaust.
  2. Crawl under and see if there's oil coming from the oil filter. You may have damaged it in your mud adventures.
  3. Pull the plugs looking for oily residue (write down condition of each plug for future reference).
  4. Pull you air intake and see if the inside is oily.
  5. Pull the PCV valve and see if it rattles. If it does then it's okay. If not, then cause may have been blowby.
  6. Pull the breather cap from the other side valve cover and note its condition.
  7. Do a visual or vacuum test on the intake manifold. Haven't done it for a couple years but it involves pulling the hose leading from the PCV valve at the intake manifold, plug the hose, and re-attach to the intake manifold. I put saran wrap over the intake manifold hose connector and push the hose back on. Remove the breather filter on the other side. Cover the breather hole something with something like a soft plastic card (palm of hand could be used with care). Have someone start the engine. In about a minute you should see card being held to hole by itself or feel suction on your palm. This means that belly pan gasket is okay. If there is no or little vacuum, then the gasket is probably blown. Did you get any pinging on the way back when going up an upgrade and putting a sudden load on the engine?
  8. If you have oil on any of the plugs, do a compression test on all cylinders.
  9. If none of the above gives an indication of oil loss, pull the valve covers and look for a broken/misaligned rocker, broken valve spring or a suspected damaged pushrod. Oil for the upper parts come up through the hollowed out pushrods.
If you don't see anything by now, then it's probably time for pro. help (if not experienced yourself). Sure hope not. I'm really hoping that you'll stop at #2 above. Carry a couple of quarts (liters) of oil around with you and drive judiciously (?) monitoring oil pressure, oil level after adequate stop time and noting/trying to locate noises.

Contributed by: Bob Tom
Last updated: Sun Oct 13 09:31:17 2002