Smoking Nissan Sentra

2000 Nissan Sentra with 105,000 miles. Runs great. All scheduled maintenance from the beginning. Grandma owned until I got a hold of it 2 years ago.

The beginning…

The car has had a slight exhaust-type smell for about a month. I thought it was either an exhaust leak or a small oil leak. I overlooked this as it was running great and I only drive to and from work at a total of 5 miles/day. I was going to be driving it about 20 miles so I figured I should just double check the oil.

Before my drive, I checked the oil and the dipstick said I had absolutely no oil. Backstory: I got my oil changed about 2 months ago and they broke the dipstick. They replaced it with a new one. I drove a few blocks to get oil. I purchased 2 quarts filled it up. I drove off and about a half a block later it started smoking bad. White smoke canvassing the whole street.

I turned around and went back to the auto parts store. I had a guy come out and look at it and he was baffled. The only thing he though was that it had run completely dry and it need more oil. We put 2 more quarts of oil in it (4 now) and it did not register at all on the dip-stick. A small oil leak was discovered coming from the head gasket (that was the smell). Also, there was no milkiness under the oil cap indicating

I decided to drive it back to work to leave it overnight. It smoked like hell and I made it about 4 blocks before it died. I pushed it the rest of the way and it stayed overnight.

The next day, I spoke to a mechanic friend. The only thing he could think of was that the dipstick was not the right size and it wasn’t reading any oil. The oil I put in was extra and the car was burning it off. He suggested I drain out all the oil and put 4 quarts in.

I drained all the oil but only 4 quarts came out. I added 3 quarts of oil and checked it again. Not it was reading about 10 times more oil than what I was supposed to have.

My mechanic friend said to start it up and the oil level should go down. I did start it up and the oil level did go down but it was reading about 5 times more oil than it should have.

That is where I am at at this point. Hopefully it isn’t a blown head gasket or piston.

I don’t want to insult your intelligence, but…I have to ask…
Are you positive that it was the engine’s dipstick that you were checking, and not the dipstick for the transmission?

If you were checking the trans dipstick, aside from the obvious problem that the trans is in dire need of fluid, you could likely have been adding oil to an engine whose crankcase was already full. Then, if the correct dipstick was checked, it showed that the engine’s crankcase was grossly overfilled.

It is possible that someone might come up with a different scenario, but this is the only one that I can envision.

My biggest fear for you has to do with driving the car with a dry transmission and a grossly-overfilled crankcase. Please don’t start the engine. Have the car towed to a competent mechanic.

On some FWD cars, the crankcase and the tranny dip-sticks can be quite close together. They are usually well marked…

I think you have an oil drain back problem, in other words the engine is sludged up bad. What is happening is that when you add oil, it is not going down into the pan, it is staying up on the head. All this oil is covering up your valve stem seals and is being sucked into the engine and making smoke, although white smoke indicates coolant so that is a different concern.


Check your coolant level and check for oil floating on the coolant. Remove your valve cover and look for the drain back holes. They should be along the inside the head, next to the valve cover rail (mating surface) on one side, most likely in the corners. You should be able to stick a long screwdriver down these drains. If you can’t, kinda work the screwdriver until you can. If you have to knock a lot of hard sludge loose, change the oil asap.

Was the oil leak really from the head gasket or the valve cover gasket?

My suggestion at this time is to have it towed to a reputable independently owned & operated shop, tell them the story, and let them check it all out.

If it were me, I’d want to check the oil and transmission fluid for its level as well as for any evidence of cross-filling. I’d also check the coolant. At that point I’d probably drain and refill both, checking the dipstick reading compared to the actual amount I had added.

A drainback problem would not manifest itself as a too-high reading after adding oil, but if it were holding the oil in the head it could cause that low reading, causing you to add more, and then when it all let go and ran down it would read high. I think it’s a goodo theory. It’s eays to test, too. If you remove the valvecovers and run the engine, you should see the oil just running out of the rocker arm shafts and down into the drains… If it doesn;t drain and runs everywhere, the drains are plugged. Don’t worry, it will not harm the engine to run with the covers off.

In short, I like Keith’s theory. But I’d want to check everything out, all the fluids, because the root cause may have been mixing of fluids because of someone using the wrong fill tube.

Again, have it towed. If VDC is right, and the fluids are now mixed, you could do serious damage by driving it this way.

Thank you everyone for the great insight. I will go over all this after work. I will keep everyone posted.