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montreal-1 · Sep 16th, 2006, 05:50 PM

Hello,

Most of the driving that my wife does with her 98 Sentra (77 k. miles) is in the city and occasionally a 2 hour trip on a flat highway at 60 mph, so her automatic transmission rarely revs the motor over 4000 rpm by my estimation. But recently we needed to drive for 10 hours straight in very hilly terrain and she insisted on going up the hills at 70 mph, so that dropped the tranny into second gear with the resulting high revs.

Within a week after returning home, we can hear a high pitched sound coming from the motor which varies with the engine speed. I thought it might be an older PS belt, so when I changed it yesterday, I could see a lot of oil around the crank pulley and the groove in the AC belt closest to the motor has oil in it, but all the other grooves in the AC belt and the other belt are clean.

When I look up at the oil pan from underneath, I see the channel on the outer edge of the pan where are found all the bolts that hold the pan to the motor - the bottom of this channel (highest surface) is coated with oil over most of its length.

So my immediate assumption was that the pan is leaking through the silicon seal and oil is flowing downward but the air currents are spreading this layer of oil around the channel, while keeping other surfaces in the same area dry. In other words, the channel may be the surface least exposed to wind that flows around the engine and any oil flowing onto adjacent surfaces will be swept away rather than accumulate there.

So I called the dealer and they want $250 to reseal the pan.

Then I came across this thread and asked myself if a leaking front crank seal could explain this oil that is present on the underside of the pan protected up in the channel.

My theory is that oil leaks out slowly through the front seal and because the shaft is spinning, centrifugal force throws it out onto the back side of the pulley, which in turn drives the oil to the outer edge of the pulley where it gets thrown out in all directions. Where ever the oil lands, it then gets pushed in a particular direction by the wind and gravity.

So could the wind and gravity push the oil film downward and under the oil pan and up again where it finds refuge in the oil pan channel? If so, then it is more likely I have a front seal problem than a leaking pan gasket problem.

How to explain the high pitched sound? It could be a bearing in the alternator, the P.S. pump, the water pump, the AC compressor, or the V-belt idler wheel.

But could a bad crank seal make such a sound? That would require metal rubbing on metal.

Does the crank seal have any metal parts like a ring or a flat washer that could contact the spinning crank shaft and create this high pitch sound?

Any comments would be greatly appreciated.

Sep 16th, 2006, 05:50 PM	#66 (permalink)
montreal-1 Nissan Enthusiast Join Date: Apr 2006 Posts: 31	Hello, Most of the driving that my wife does with her 98 Sentra (77 k. miles) is in the city and occasionally a 2 hour trip on a flat highway at 60 mph, so her automatic transmission rarely revs the motor over 4000 rpm by my estimation. But recently we needed to drive for 10 hours straight in very hilly terrain and she insisted on going up the hills at 70 mph, so that dropped the tranny into second gear with the resulting high revs. Within a week after returning home, we can hear a high pitched sound coming from the motor which varies with the engine speed. I thought it might be an older PS belt, so when I changed it yesterday, I could see a lot of oil around the crank pulley and the groove in the AC belt closest to the motor has oil in it, but all the other grooves in the AC belt and the other belt are clean. When I look up at the oil pan from underneath, I see the channel on the outer edge of the pan where are found all the bolts that hold the pan to the motor - the bottom of this channel (highest surface) is coated with oil over most of its length. So my immediate assumption was that the pan is leaking through the silicon seal and oil is flowing downward but the air currents are spreading this layer of oil around the channel, while keeping other surfaces in the same area dry. In other words, the channel may be the surface least exposed to wind that flows around the engine and any oil flowing onto adjacent surfaces will be swept away rather than accumulate there. So I called the dealer and they want $250 to reseal the pan. Then I came across this thread and asked myself if a leaking front crank seal could explain this oil that is present on the underside of the pan protected up in the channel. My theory is that oil leaks out slowly through the front seal and because the shaft is spinning, centrifugal force throws it out onto the back side of the pulley, which in turn drives the oil to the outer edge of the pulley where it gets thrown out in all directions. Where ever the oil lands, it then gets pushed in a particular direction by the wind and gravity. So could the wind and gravity push the oil film downward and under the oil pan and up again where it finds refuge in the oil pan channel? If so, then it is more likely I have a front seal problem than a leaking pan gasket problem. How to explain the high pitched sound? It could be a bearing in the alternator, the P.S. pump, the water pump, the AC compressor, or the V-belt idler wheel. But could a bad crank seal make such a sound? That would require metal rubbing on metal. Does the crank seal have any metal parts like a ring or a flat washer that could contact the spinning crank shaft and create this high pitch sound? Any comments would be greatly appreciated.