I was under the car today and noticed sooty staining that was evidence (to me) of an oil leak.

In the picture, you will see the A/C compressor at the center. Down and to the right, you will see a whole bunch of black, oily soot.

Question: Where is my oil leak coming from?

Thanks.

Pic 1


Pic 2


Pic 3

 

Must be a slow leak from the pan right? Can't be from filter if it's clean beneath it, right? Looks ok to me if you're not in hurry for perfection. I know it's hard not to fix something if you see it could be done. Best of luck, Clay

 

I added two pics this morning (see above).

@claycolvin Thanks for the post. I don't know what to call the "oil pan" since it's part of the transmission case. I did not see oil leaking from the oil filter or oil drain bolt. You're right, I cannot see what's going on. Right now, I'm concerned that something on the serpentine belt-side of the engine is leaking.

 

Hello Mister,

It may be an AC refrigerant oil leak from the compressor. Whatever it may be, its an "old" leak, possibly even completely stopped (or its all leaked out). The sooty look is likely road grime.

Don V.

 

@Outfit Thanks, Don.

 

This looks like the pathway of the leak to me, though I can't see it perfectly. It may be a very thin streak, but I'd recommend following it to the highest visible point to find the culprit.

 

@Pyts Sorry, old friend, but I beg to differ. Your yellow line and everything to the right of it is not the problem. The problem is to the left of your yellow line.


Question: If I were a mechanic, and I wanted to get a look at the rear side of the engine (the spark plug side, the side that faces the fire wall), how would I do that ?


I had another look at the engine today — a look from the engine bay, not from underneath — and the serpentine belt-side of the engine looked fine, but I am wondering if the oil leak is on the spark plug side of the engine. From what little I could make out, the oil may start at the valve cover. There's a chance that the oil is coming from a bad valve cover gasket. If not, then what else is on the back side of the engine that could be leaking?

 

There's probably some fancy equipment out there, and I bet someone who's been at it for 30 years has a particularly shaped makeup mirror they affixed to a nameless piece of a tool, and it curves just right to work for nearly every situation.. I don't have anything like that..

All I can advise is that you can pick up a cheap telescoping mirror and try your luck, or you can remove the top-side cowling, try to snake your arm into the spot with your smartphone and take some blind pictures with the flash setting on, review and adjust your angle on re-attempt. If I had to guess what most general mechanics would do, it would be: make an assumption based on familiarity with the engine. Or a rookie at the dealership or the lube shop would say you have a leaking cv shaft seal.. replace it and see you back when it doesn't work.

You could guess, though, that where dissimilar materials mate, there would be likelihood for a leak, like with the valve cover. Or if the pcv system hasn't been maintained, maybe valve cover again, unless there's reason to assume otherwise. Or factor in what's close to the most significant heat source, the exhaust manifold. if you had an exhaust leak, it would be safe to assume that seals and hoses near the leak would give out at some point..

That's the best I can offer, unfortunately.

 

Looks like the ac is connected directly to the large oil pan. Check torque on oil pan bolts, clean it all up with brake clean and check it again after a run?
What I would try. Best of luck, Clay

 

I would think the freon would come out before the oil in the compressor. Could leak both, but a loss of freon would be guaranteed right? No loss of freon, no leak I would think. Clay

 

I'll keep this in mind. This looks like oil. I don't know what a freon leak would look like.

 

My 2 cents...aka guess. Engine front main seal seeping ever so slowly?

Mark

 

Thanks. This is what I want, some good guesses. I wish I had a diagram from the service manual that showed all of the spark plug-side of the engine.

Your PVC guess is a good place for me to start, but I thought the PVC valve was on the front side of the engine. I will take a look at the manual.

So, for all of you sports fans out there who are paying attention, here's is the question: What is on the back side of the engine that could be leaking oil?


EDIT: Now that I look at the picture (above) again, I don't know how a leak on the back side of the engine could so thoroughly reach the front side where it mates to the air conditioning compressor. The oil would have to travel upward. Hmm.

 

Thanks. I hope you're wrong. I'll look at the manual and figure out where I have to look on the engine.

 

Also, is that a drop of wet oil on the splash shield?

 

Hard for me to say. As you can see, I was in the middle of an oil and filter change. That drop could have been unrelated to the leak.

 

May not be of much help, but here are 2 pics that may give you a better look at what's what where you can't see with your engine in the car.

 

@zcargo That is helpful. Thank you very much.


I don't see anything on the back of the engine that could be the source of this leak. Even my earlier idea that the valve cover might be leaking seems like a stretch.

Yesterday, I was looking at the Service Manual and some youtube videos, trying to learn something about the air conditioning compressor. Evidently, the compressor does contain oil, and there is a relief valve of some sort. But I'm still lost on this.

 

@Mister Coffee I would agree that there's not much on the back of the engine to leak but the valve cover.

As @claycolvin stated, I too would think your loss of Freon would be more evident. Does your compressor still come on when you turn on the AC? If not, this might lead to a potential AC compressor leak conclusion. The compressor circulates a small amount of oil with the Freon to lubricate the internals. A gas would tend to escape before the oil, I would think.

Mark

 

@zcargo Thanks, Mark. The AC appears to be working normally.

Next step might be to lift the car and start taking things off: wheel, wheel well liner, every cowl that's blocking the view, etc. A pain in the neck I'm not up for this week, but maybe soon.