I was running my T last weekend and noticed when I opened the oil fill cap, smoke started coming out of the cap. Is this unusual?
Like a wisp of smoke, or "I can't see my hand in front of my face" smoke?
If the engine runs fine otherwise, I wouldn't worry about a wisp of smoke.
Lots of smoke may mean that the piston rings are worn out, try doing a compression test.
Smoke or oil vapor ? Oil vapor is normal.
I had a car with blow-by so bad it would blow smoke rings out the breather cap. Ran like that for years until the transmission crapped out! It is not good but it ain't all that bad either.
Take a compression test. You might learn something.
To add a bit to what Charlie B. just said, take a compression test, and record the readings for each cylinder as you go along. If the readings on one or more cylinders are low, go thru' all cylinders again a second time. Add a tablespoon or so of motor oil to each cylinder (one at a time) and record each compression reading as you go along and compare the "wet" and "dry" readings of each cylinder. If a cylinder shows a considerable increase in compression with the oil, that would indicate that the oil sealed up worn rings somewhat, but if the second reading is still about the same as on the first go-round, that would indicate that the low compression in that cylinder is due to a leaking valve.
As Charlie B. said, a compression test can tell you a lot,.....especially a "wet" and "dry" test,.....FWIW,.....harold
Thanks. I will check it out. I will first make note if the "smoke" smells like burning oil or if it could be a little condensation in the block just boiling. At the time, it seemed like it could have been exhaust, but I will check it out.
If the car otherwise runs good, with no complaints, just ignore it.
If it isn't coming out the tail pipe I ignore it. That includes any white I see in the oil filler hole.
That cap should have a screen and open to the air. it is called a "breather". When the pistons go down they actually compress the air below them but the other two pistons go up at the same time so the air would theoretically not build up pressure in the crankcase. There is always a small amount of gasses which make it past the rings and some which goes through the valve guides into the crankcase, and so it goes out the breather. So if you had just turned off the engine, you probably saw some of that gas.
It is only when the wear on the rings and valve stems gets excessive that you will get a great amount of smoke coming out of the breather. You would be most likely to see it with the engine running. Sometimes it gets so strong that it gets inside the passenger compartment. If it is excessive, you need to do some engine work. Maybe ring and valve job, and maybe rebore and new pistons. You would need to take the engine apart to determine just how much work is needed.
I have had a few cars in the past that had "blow by". Some more and some less. Sign of a slightly worn engine. If the engine is not rattling you are still ok. We had a 50 Ford when I was growing up that was a smoker and a few others along the way. It's nothing uncommon.