1991 Nissan Sentra Excessive Oil Burning

Tiny
MINIDRIVR
  • 1991 NISSAN SENTRA

Engine Mechanical problem
1991 Nissan Sentra 4 cyl Front Wheel Drive Manual 227000 miles

Recently the crank seal and valve cover gasket started leaking. I replaced both.

Next time I drive it, the car is smoking (blue) and stumbling when shifting. Just as you let off the clutch and accelerate. It also pings about half the time just as it belches out a large cloud of smoke.

I've replaced the PCV valve and found the 2 vent hoses coming off the valve cover soaked in oil. Prior to changing the valve cover gasket these hoses were dry.

The car burns 1 quart in about 150 miles. Highway speeds no smoke is visible. From a stop, up through the gears it smokes (cloud larger than the car).

Prior to the crank seal and valve cover gasket, the car burned NO oil. Not a drop in the 227k miles before this. The car also just passed CA smog with no problems less than 1 month ago.

Any ideas? I replaced the seals around each sparkplug tube and the PCV valve. I tried 2 valves, one aftermarket, one from Nissan. The 2 vent hoses from the valve cover were reinstalled properly.

On the inside top of the valve cover is a baffle that separates the PCV vent and breather tubes from the valve train. This baffle is sealed around 3 of the 4 edges and takes up about 2/3rds of the area inside the cover. At one end there is a slight edge where I assume it lets the area "breath" through the PCV and other vent hose to the intake. Is there something above this baffle that could have dislodged and is no longer keeping the intake from drawing oil off the valve train? The baffle is riveted in place so there is no easy way to remove it.

Still getting 36-40 mpg even with 1 quart per 150 miles of driving!

This is the second crank seal I've put in it (original lasting 170k) and the first time the valve cover has been removed.

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Tuesday, February 10th, 2009 AT 12:13 AM

15 Replies

Tiny
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No ideas?

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Tuesday, February 24th, 2009 AT 7:27 PM
Tiny
BEFLAND
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Did you find out what is causing this? I have the exact same problem after a valve cover gasket replacement.

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Wednesday, April 1st, 2009 AT 10:37 AM
Tiny
MINIDRIVR
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I still haven't found a solution. I also tried using compressed air to blow through the vent tubes to make sure there was air flow through that "plate" on the inside of the valve cover. It has air flow so I am completely confused.

It's using 1 quart every 115-150 miles (depending on how much freeway driving I do). It's running much worse as well due to the oil residue buildup. I've had to switch to premium gas to keep it from pinging.

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Wednesday, April 1st, 2009 AT 11:13 AM
Tiny
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If you take it to the dealer, let me know what you find out. I'll post an update if I ever solve this.

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Wednesday, April 1st, 2009 AT 5:35 PM
Tiny
BEFLAND
  • MEMBER

Will do. I've got to find out pretty quick because I can't drive it the way it smokes now. I'm almost sure it has to be something related to the PCV or hoses. Either the aftermarket valve was no good or I knocked something loose when I installed it. Maybe loosened something when I cleaned the underside of the valve cover?

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Wednesday, April 1st, 2009 AT 5:49 PM
Tiny
MINIDRIVR
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I tried an aftermarket PCV and one from the local Nissan dealer. Neither one worked any better than the original one I was replacing.

Good luck!

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Wednesday, April 1st, 2009 AT 6:58 PM
Tiny
BEFLAND
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OK.I replaced the PCV with another aftermarket one. I also replaced the hose from the PCV valve to the manifold (even though I believe it was ok). But before I put the hose back on I took a tiny screwdriver and scraped out inside the fitting that screws up into the intake. Then I took a shop paper towel (the industrial kind not the kitchen variety) and twisted it so I could get it up in the fitting. I also did the on the valve cover where the PCV screws into. After burning off the oil that was already in the system it has not smoked and it is running normal. I'll check again in a while when I go out at lunch but it seems to be fixed.

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Thursday, April 2nd, 2009 AT 8:11 AM
Tiny
MINIDRIVR
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I had tried that on mine last month but it didn't help for very long (day or two). How many miles do you have on it?

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Thursday, April 2nd, 2009 AT 7:06 PM
Tiny
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Any update? Did that fix it for good for your car?

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Saturday, April 11th, 2009 AT 12:24 PM
Tiny
BEFLAND
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Well it quit smoking but it's still using about 1 qt of oil every 100 to 150 miles. I cannot figure out where it's going. My steering rack is leaking fluid so it's hard to tell if there's oil leaking from somewhere too. It's not leaking around the perimeter of the valve cover and it doesn't seem to be burning it. I noticed when I took the valve cover off, there were some plastic pieces mounted to it. Didn't see where they mated to anything on the head. What purpose do these serve? Also.I assume that the cover goes in some kind of seal around the plugs. Wonder if I could have damaged one of those?

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Wednesday, April 15th, 2009 AT 6:26 PM
Tiny
MINIDRIVR
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That sounds similar to mine. Mine seems to give clouds of smoke if I drive on the highway at sustained rpms, then wait at a stop light. When I take off, pinging, puffing smoke. Some days I will never see it smoke. But it always uses 1 quart per 150 miles. Sometimes it's used 1 quart in about 100 miles.

Once in a while it smokes at each shift before the temp gauge has come up to normal.

Have you had anyone follow you to watch for smoking? Mine puts out puffs of smoke every 2-3 minutes on the highway. But it doesn't rise above the trunk lid and it dissipates quickly so it's not visible from inside the car.

This is all just really odd since the car used no oil in the 225k miles before I replaced the valve cover seal. Which is no longer leaking and the crank seal is holding fine. Actually there are no oil leaks at all on the car.

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Wednesday, April 15th, 2009 AT 9:21 PM
Tiny
BEFLAND
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That is EXACTLY the same scenario as mine. Only my car has only (LOL."Only") 198K miles. But no oil usage up to changing the valve cover gasket. I did not change the crank seal so I might be leaking a little there but I don't think so. Looks like further investigation is required. I'll let you know what I find out.

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Thursday, April 16th, 2009 AT 7:32 AM
Tiny
BEFLAND
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OK...finally fixed! I tried another PCV, PCV hose, re-installed the original PCV, etc. I finally (even though I couldn't see why) installed a different valve cover. I took a valve cover off of another sentra I have (for parts), installed a new gasket but left the old PCV valve in the cover...and installed it on my driver. No oil usage what-so-ever. I have no idea why this worked. The cover I took off was pristine inside. The one I installed had sludge all in it (I didn't clean it!). It has to have something active in the top of the cover underneath the riveted in windage tray. It must be related to the PCV system because I saw no other signs of oil consumption (No oil in the air filter, etc). Here are some pictures of the valve cover I took off.


http://www.2carpros.com/forum/automotive_pictures/338786_DSCN9951_1.jpg



http://www.2carpros.com/forum/automotive_pictures/338786_DSCN9952_1.jpg

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Thursday, May 14th, 2009 AT 2:03 PM
Tiny
MINIDRIVR
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Thank you for the update. I have been wondering about switching the whole cover out as well. Guess I'll take the plunge and save some oil.

Thanks again!

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Thursday, May 14th, 2009 AT 8:37 PM
Tiny
MINIDRIVR
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I just wanted to give an update in case anyone runs into this thread will searching. Just like befland, I replaced the valve cover. I didn't want to take the chance of picking one up at a junk yard and have it still smoke. I bought a new one from Nissan. Online of course, my local dealer wanted more than double what i paid for it online.

Replacing the valve cover stopped the oil use. The car is back to it's normal, no oil use. Almost 800 miles since, still right to the full line on the dipstick. The car also runs much smoother and no longer pings, just like before this started.

The valve cover looks just like the picture posted previously. I was curious what is above that metal plate so I pried it off partially. What I found underneath is basically nothing. It does not have any baffling or filtering material in that space. Both the PCV valve and the other vent off the cover go into this area above the plate. The plate has a RUBBER seal around it. That rubber seal is the only thing preventing oil from getting to the intake.

What happened with my car was when I replaced the valve cover gasket, some of the brake cleaner I used on one tough deposit must have run under that plate, onto the rubber seal. A day later, it had damaged the seal enough to allow oil to be drawn into the the sealed portion under the plate and up into the intake.


http://www.2carpros.com/forum/automotive_pictures/315551_P6050003_Medium_1.jpg



Closeup of the seal. Not necessarily where it was damaged though.


http://www.2carpros.com/forum/automotive_pictures/315551_P6050004_Medium_1.jpg

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Saturday, June 6th, 2009 AT 12:29 AM

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