Engine oil misting my rear window?

Hairball · Dec 30th, 2003, 11:19 AM

Hmmm... This is kinda wierd. Couple of months ago, took a trip up to Crossville, TN. For me, this involves climbing up some pretty steep grades. Had me + a buddy of mine + Dog + 250lbs of cargo = about 775lbs. When we arrived, I found that the entire rear of my Pathfinder was lightly coated with what appeared to be engine oil (ie. brown, not red). There was some oil dripping from the engine, but the oil level was fine. Now, I had just had the oil changed the day before, and the problem did not repeat itself on the (downhill) trip back. I went back to Jiffy Lube, and they were kind enough to change my oil again for free

, but they could not tell me where the oil was coming from. I have made this trip again twice more. The second time, I was unloaded, and the problem did not present itself. The third time, I was lightly loaded, and I got a very light coating. It seems that this problem only happens when the engine is under heavy load / high RPM. Now, I have always taken pains to avoid redlining the engine, and I change my oil regularly. I would like to install a trailer hitch, but now I am very hesitant.
Now, where on earth could this be coming from, and how can I fix it? Could it actually be transmission fluid? None of this sounds good.
Thanks again.

Mark

jadcock · Dec 30th, 2003, 11:38 AM

My first guess would be that it's coming from the tailpipe. That's really the only possible source if you're getting a haze on your rear window. How many miles are on your truck? Perhaps the engine is a bit tired and it's using a lot of oil trucking up the long grades under heavy loads. Any correlation to outside temperatures, or does it do it both when it's hot and cold out? Have you noticed increased oil consumption recently (especially on those trips)? Check the inside of your tailpipe -- are there heavy sooty deposits or is it relatively clean?

I really doubt it's coming from the engine. I suppose it COULD be coming from your rear differential (oil gets vaporized, and trapped in the vortex behind your truck and deposited on your window), but I think that's pretty far-fetched. I'd say your first course of action is to check your tailpipe out -- if it looks sooty or if you noticed any oil consumption, I think the problem is internal to your engine (worn rings maybe).

96R50 · Dec 30th, 2003, 03:08 PM

Have you looked at the rear differential for signs of an oil leak? Or possibly the seal on the slip joint at the rear of the transfer case for the rear driveshaft. The misty brown oil covered tailgate sounds a lot like the rear differential to me. The 4 runner that my friend wheels had a leaky differential and the tailgate was always a mess with oil and road grime.

Hairball · Dec 30th, 2003, 04:50 PM

Well, I guess that is better than a blown seal or gasket on the engine. Although I can't imagine why this would only occur under high load conditions. Thinking back, there was a fair amount of engine oil in my brush guard. Perhaps the tech who changed my oil allowed a quantity to collect and it blew out under the chassis.
BTW, I wiped in and around my tailpipe with a paper towel and was only able to get a little stain of carbon. So I don't think that I am burning any oil.

lovemysan · Dec 30th, 2003, 08:49 PM

What about the pcv system. Could there be an issue with the pcv valve.

Bror Jace · Dec 30th, 2003, 11:25 PM

I've only seen one car recently which burned oil bad enough to coat its backside with a mist of oil and that was an 80's vintage Acura Integra with well over 150,000 miles on it. It was my friend's. He bought it used and would wring the snot out of it most of the time. I was with him when he got it and I don't think the original owner was much gentler on it.

I figure the thing broke an oil control ring ... or the packs of rings were impossibly stuck in their grooves. The thing used a quart of oil every 1,500 miles or so and the back of the hatchback was brown/black from the oil and the dirt the oil attracted. Took a serious Simple Green bath to get it off ... and a few months later it would be back. Switching to 20W50 did not significantly reduce oil consumption.

If your truck burned oil like this, evidence of this mess would be a more consistent thing, I'd think.

Have you considered that you might have driven through something or parked under a tree which was dropping sap? Maybe parked in a spot which was downwind of someone spraying something ... like a pesticide? When I was a kid my mother's car was downwind of some site where they were spray-painting and the car got covered with overspray.