Nissan Repair: Nissan Sentra 1994, racking noise from the engine, nissan sentra 1994, nissan sentra

Question
Hi, please i drive a 1994 sentra. The engine racks heavyly after a I speed above 100 mile per hour and then a blue smoke comes out of the exhaust system. It also happens when I then on the ac as well. Any suggestions would be welcome gratefully.

Answer
Naab,

The engine noise is probably caused by lack of oil at the crankshaft.  When you drive that fast the oil does not have time to drain back to the pan and you end up running the engine dry of oil.  I would suggest that the engine be removed and taken a part to inspect the main bearings and the rod bearings.  The blue smoke is from too much oil beign trapped in the valve cover and then getting sucked down the valve guides.  The remedy for all of this would be to relieve the oil drain back holes in the head to allow for the oil to drain back faster.  Also, a large capacity pan to hold more oil would help since it would allow for more oil to stay where the oil pump could get to it.  A dry sump system would be the obvious solution but they are quite expensive.  If the airconditioner causes the engine to load to the point of causing blowby would mean that the rings need to be replaced too.  I would rebuild the engine and releive bthe oil drain back holes as a minimal.  Then, I would break the rebuilt engine with 5W30 weight oil.  After 1000 miles I would switch to Mobil 1 Synthetic 5W30.