Where does the engine oil leak from?

[njjoe]

Originally Posted by BlueHorse

Does anybody know whether there is a gasket, crush washer or some type of sealant (teflon tape?) between the oil pressure sending sensor and the surface of upper oil pan?

BH-

According to the 2005 Service Manual the sensor uses RTV as the gasket and is torqued to 11 ft-lbs.

-njjoe

[BlueHorse]

I cleaned up the whole area and after 400 miles checked again today. Can visually confirm no oil leak from oil cooler mating surface, nor oil pressure sensor mating with the upper oil pan, nor from lower oil pan gasket.

What surprised me is there appears to be some small amount of oil on the oil pressure sensor wires. If you refer to 1st photo in post #19, you can see it was soaked with oil back then. The oil did not come from the outer end of the sensor, but instead appears to be coming from the other end of the wire going above.

There is a bracket holding this wire in place - refer to first photo of post #22, you can see the bolt holding down the bracket and wire. The oil I observed today is from the bolt going up to at least 6 inches. No oil seen below this bolt, and no traces of oil seen on any of the aluminum surface in the area (including surfaces 1 feet above the bolt as far as I can visually see).

I know I have some tiny seepage in the bank 1 valve cover, but that was small and the location was facing the driver side, as opposed to facing the passenger side. The oil pressing sensor wire is ~1 to 1.5 ft jump to the passenger side (right side) from where the engine valve cover seepage is.

I can't see any oil leak from above the valve cover facing the passenger side.

What does the oil pressure sensor wire go on the upper side? Given all aluminium surface is so clean, could it be oil leaking from this upper end of the wire and traveling inside the shield cover of the wire until I can see it at the bottom?

If the PCV valve is blocked, will oil leaking out fit my pattern here?

Thanks!

[mozo1]

Hey,

I have the same problem you have. My 2006 MO consume engine oil these days more than before. It reads 227k and I used to use CASTROL synthetic oil on it, and change every 10k. But now since it consumes about 2.5 litters between oil changes I switched to regular oil. (As I know synthetic oil evaporates more often in engines that have high mileage, so switching to thicker oil will reduces oil loss.)

Anyway, I see some oil leak -could be seepage- in area #A under both green sinceros.

How could I stop that from leaking?

[mozo1]

A picture of it

[BlueHorse]

Originally Posted by mozo1

A picture of it

Mozo1,

The oil you saw near the green connector may not be oil leaked else where travelling there. And your 2.5 liters loss of oil may not be here either. I cleaned up in my car this area a few K miles back and have not seen any oil coming back there.

As my post #32 pointed out, most of my oil, if not all, seems to be leaking somewhere above the pressure sensor connector wire, and travels down that wire. I seem to lose more oil per driven mile during long trips (150 miles plus a trip) vs. local short commute. That tells me MAYBE the leak is due to blocked valve can't handle oil flow after engine is fully warmed up. Still don't know where exactly. I am thinking to wait till the car hits 120K miles (currently at 100K miles) and due for spark plug replacement, then will take a closer look then.

[mozo1]

^
Good luck then, keep us updated.

[Pilgrim]

Keep in mind that any oil leak which is of consequence usually coats the lower parts of the engine in oil. A leak that shows for an inch or two around a connector or joint isn't a leak of real consequence. If you're leaking enough oil to notice it on the dipstick, you will have a MESS on the underside of the car, and oil dripping onto the ground when you park.

Granted, oil leaks are unsightly and undesirable, but they're not generally responsible for oil consumption...that's due to the engine burning it.

I like the idea of checking it out when you do the plugs - you'll have a better view of things then. If you are indeed leaking more on longer trips, it may be because the oil is getting hotter and therefore wicking through openings better than in local trips when it doesn't get at hot. It's also worth checking the PCV valve (I don't know where it is on this engine) as that's responsible for venting crankcase pressure, and increased pressure could certainly result in more leakage.

[mozo1]

Now look what I found under gearbox




Although I don't see any oil drip beneath the car.

Do you guys think it's the reason behind MO engine oil leak?