Burning smell coming from engine?

July 21, 2006 4:18 PM

Burning smell coming from engine after not being driven for a year. Any ideas?

I have a 97 jeep wrangler (6cyl, sport) that had not been driven for about a year (long story). After getting a tag this week, I changed the battery and took it in for an oil change. I then gave it a test drive (10 miles or so), and all seemed normal. About a half mile from home, however, I noticed a burning smell coming from the air vents. The same burning smell you get when passing someone laying tar or doing road/roof work. When I pulled into my driveway I raised the hood and confirmed the smell was coming from my engine.

All the gauges are normal, and the engine seems to be running fine.

Any ideas what this might/could be?

posted by gtr to Travel & Transportation (13 answers total)

Probably sludge from the old oil burning off in the engine. If it doesn't go away quickly you'll need to get your engine flushed.

Actually, if it sat for a year with the oil in the engine you should probably have it flushed anyway.
posted by Dipsomaniac at 4:25 PM on July 21, 2006

Oil seep from the valve cover gaskets leaked onto the exhuast manifolds. When the manifolds get hot the oil smokes off. Might take a few hundred kilometres to completely burn off if you have cast iron monifolds.
posted by Mitheral at 4:27 PM on July 21, 2006

Response by poster: Thanks to both of you. (I'm having trouble marking both as best answers, strange)

If I can end with one more, how much, in general, am I looking at to get it flushed?
posted by gtr at 4:33 PM on July 21, 2006

I have a '95 wrangler that has endured two year-long periods of not being driven. During these times I have not drained the motor oil, even though I should have, and all has turned out okay.

Since I'm a believer in checking the easy and cheap before looking into more exotic problems, it could be as simple as a sloppy job with the oil change. When the oil filter is taken off oil can run down the side of the engine block. This will burn off eventually but be pretty smelly as it does so.

It's a jeep so you should have enough room to crawl under it and look for any gaskets that are leaking around the engine. If that sounds crazy to you, take it back to the place that changed your oil, mention the burning smell, and see if their grease monkey can look it over and tell you they see any leaky gaskets. They are not in the business of changing engine gaskets (assuming you went to a Jiffy-Lube type place) so you can trust them to be honest about what they see down there.

Also, make sure the engine oil filler cap on top of the engine is still there... sometimes oil change guys can forget to put it back on. Keep an eye on your oil level until you know whether or not you are burning oil, if it's leaking out, or if your engine is okay.
posted by peeedro at 5:23 PM on July 21, 2006

I think burning oil is the fairly obvious culprit. Either the techs that serviced the car spilled a little that is now burning off, or like was mentioned, you had a leak somewhere. If you continually park in the same spot, I would place a flattened box under the motor and see if the leak continues. Also, I know Jeeps have fairly spacious engine bays, so try to wipe down what you can or even go pick up some engine degreaser and clean up the engine bay. The beneficial part about cleaning the motor is that if you do have a leaky gasket somewhere, it should reappear after the cleaning. Then you know what you need to fix.

Do you notice any smoke on startup or under acceleration? You could also be burning oil due to worn piston rings/cylinder walls. Is the truck in generally good condition or has it seen better days? Though this seems like it isn't really the problem, you can pull a spark plug and take a look and see if resembles any of these. Probably a good idea anyways, just to see if there may be anything going on with the motor that might need to be addressed.
posted by ninjew at 5:51 PM on July 21, 2006

Squirrels
posted by Napierzaza at 7:37 PM on July 21, 2006

Any internal oil burning would go out the exhast pipe you would not smell it.
posted by hortense at 8:01 PM on July 21, 2006

Any internal oil burning would go out the exhast pipe you would not smell it.

Unless there's a leak around the manifold. Wouldn't have to be a big one, either.
posted by Dipsomaniac at 8:05 PM on July 21, 2006

Any internal oil burning would go out the exhast pipe you would not smell it.
posted by hortense at 10:01 PM CST on July 21

Not only would you smell it, it tends to produce a very obvious blue cloud. Unless it's a very minor blow-by, you're definitely going to notice it. However, if you're talking about a motor that does tend to consume oil on a normal basis (say 1qt between 3,000 mile oil changes), then it truly is not enough to notice.
posted by ninjew at 8:28 PM on July 21, 2006

It could also be simple dust, combined with the little bit of oil on the outside of the engine. Just like electric furnaces smell nasty when they are turned on the first time in the fall.
posted by Doohickie at 8:34 PM on July 21, 2006

You should look out for mouse nests in the engine compartment. I've seen them use the aircleaner or the area underneath it and pack it full of grass and seeds. Might be a good idea to carry a fire extinguisher for a while. Actually, you should always carry a fire extinguisher, I have since a friend told me about watching his classic corvette burn to the ground right in front of him. Evidently the combination of fiberglass and magnesium rims makes for a really hot fire.
You could also go to the car wash and gently powerwash the engine. Becareful, the pressure can drive dirt into seals and make them leak later.
posted by 445supermag at 8:12 AM on July 22, 2006

Seriously get the engine flushed. About $100 depending on where you live. Makes the car drive like new, too.
posted by radioamy at 11:05 PM on July 22, 2006

Response by poster: Thanks to everyone who commented. Everyone was a huge help. I drove the next day, after making sure there were no nests etc, and haven't had the smell since. So I'm guessing whatever it was burned away.

I'm looking into getting it flushed later this week.
posted by gtr at 8:39 PM on July 23, 2006