Severe oil leak in a 93 Nissan Sentra, 1.6 liter engine, 2~ quarts a day

nissan
sentra

#1

So, on Sunday my brothers were over to help me with some basic car stuff, mainly an oil change, since I’m not a car person. They also took off the valve cover to clean out the inside around the spark plug cylinders, put in a new seal for the throttle body gasket, and replaced the lining and o-rings in the valve cover. Since one’s a mechanic and they both know a lot about cars, I wasn’t worried. After putting everything back together, double checking everything was tight, reconnecting lines, etc, the car seemed to be fine and running better than usual.
Cut to wednesday morning, as I’m getting off the freeway going to work, the oil light starts flashing, turning off as I accelerate and on as I slow or idle. It was too dark to check anything, so I just parked and went to work as normal. When I got out I checked oil, and found it was completely empty.I took it to my bothers garage, only a few minutes away, and he checked everything again, but couldn’t find any reason for the huge oil loss. There was nothing leaking. and no evidence of it. Its like the oil is just vanishing. He did a second oil change to see if there was anything in the oil to give a clue, but there was barely any at all. We did notice that the exhaust had turned white-grey, mainly when accelerating, which made him think it was a blown head gasket, but we checked and that was fine, and there were no other signs of a head gasket problem. The oil is obviously leaking into the exhaust but we have no idea from where.
The car still runs fine, no noticeable problems other than the exhaust and rapidly declining oil. We plan on taking a more thorough look this weekend, but we’re at a loss of where to start, having checked all the obvious problems. Does anyone have an idea of what might be wrong? It would help alot.


#2

If you’re certain there are no leaks then the engine has to be burning it.

If you’re certain there was no oil consumption issue earlier then you have to look at the possibility of:

  1. There’s an error with the PCV hosing during the valve cover gasket replacement leading to a pressurized crankcase and oil being forced past the piston rings.
  2. Someone didn’t add enough oil.

And are you saying that “took” means “drove”? If so and with the oil that low odds are there is some damage no matter how well the car appears to run. That may show up sometime in the future.


#3

You say leak in the title then say there is no obvious reason for the oil loss. A leak this large would be obvious.

This is what is known as a “clue”. Apparently the engine is burning something that it wasn’t before, i.e. oil. My personal thought is you need a car, or at least an engine, and your mechanic/brother just doesn’t want to tell you that.