Why is my engine pushing out oil?
Question:
I have a 292 cid Y-block installed in my 1956 Ford pickup. The engine was rebuilt some time ago and has always run fine. I recently decided to repaint the truck and pulled the engine to detail it at the same time. The manifolds and accessories were removed in the process but nothing was disturbed internally.
Since it was reinstalled it has been pushing oil out of the road draft tube. After you run it and shut it off, it will leave a puddle.
It doesn’t smoke, have blow-by or have any other oil usage issues. I’m assuming that it is building up pressure in the crankcase somehow and it may be related to its removal and reinstallation. I’m just wondering if you have any idea what could be causing the problem.
Answer:
Oil coming out of the road draft tube normally indicates excessive crankcase pressure. In some cases, excessive crankcase pressure does not indicate a problem in the engine beyond an inability to adequately vent normal crankcase pressure. If the pressure doesn’t vent out then it builds up and eventually forces its way out past weak points. In your case, however, the road draft tube is apparently clear, so it is likely that the excessive crankcase pressure that’s forcing oil out of the tube does reflect an internal engine problem. The usual cause is excessive blow-by, which is to say too much of the combustion chamber pressure is blowing by the piston rings and getting into the engine’s crankcase.
I would suggest starting your diagnosis with a leak-down test, which will tell you how well the piston rings are sealing against the cylinder walls.
If sealing is bad, disassemble the engine to determine why. If the sealing is good I’m afraid you’ll still have to at least partially disassemble the engine in order to have a look inside.
Perhaps you forgot something when you reassembled the manifolds and accessories after detailing?
For example, was the oil baffle removed and forgotten? Did you put the push rod cover back in place? Is it properly sealed with a new gasket?
