Hello, wonder if anyone has an explaination. My 94 nissan altima began burning oil heavily this evening unlike any time before. The smoke came from a place beneath the alternator. I checked the engine and it was a little low on oil but not enough to cause any overheating. When looking at the engine there seemed to be oil coming out the front and some was leaking below. I recenly used 5w-30 by quaker state for engines over 100,000 miles. Do you know what may cause this to occur, or what this is a symptom of? Thanks
There are a number of gaskets that can leak oil onto your hot engine, it isn’t surprising that this would happen in a 15 year old car. Gaskets rot, dry out and crack, it just happens. Have it checked out, it likely will not cost a fortune to have repaired.
It could possibly be that the PCV valve has become stopped up. This will pressure up the crankcase and force oil out past seals.
This is what it looks like and it’s cheap.
Remove it and shake it. If it rattles like a rock in a can then it’s good. If it does not rattle or the rattle is erratic or muffled then it’s defective. If gummed up, it’s also possible to clean it but considering the fact they’re dirt cheap might as well just change it.
How many miles does it have on it?
Was it burning oil before? How much?
First check or change the PCV valve as OK suggested. In my mind he’s “the man”.
However understanding what’s happening might also help. As your engine runs it builds pressure in the crankcase from small amounts of combustion gasses that blow by the pistome. That pressure is normally relieved through the PCV valve and the crankcase fumes ingested into the engine. If the PCV valve is clogged, or if wear has gotten to the point that the pressure becomes substantial, the pressure in the crankcase can force oil out various gaskets and seals that normally hold it in. A key seal is the “main” seal. That’s a rubber seal around the crankshaft, and since that has a spinning shaft up against it it’s particularly subject to long term wear. Being rubber, it also gets old and shrinks.
Since the oil that lubricates the valvetrain drains down to the crankcase through open “return channels” from the head, the crankcase pressure also extends to the spaces under the valvecover gaskets. Being under pressure, the gaskets can take a “set” over time, effectively reducing the pressures with which they seal. Behind these gaskets are “galleys” in which the oil collects to drain back into the oilpan. If the gaskets are tired and the pressure under the valvecovers builds, that can force oil past the valvecover gaskets.
Both of the above areas can leak oil, and the valevcover gaskets in particular can leak it onto the hot exhaust manifold where it can burn.
Hope this helps.