1931 Roadster, oil drip in reverse

[handlebar99]

I drive my roadster on average 50 miles per week -- trips to Lowes/Home Depot, ice cream, etc. runs fine, no problems. Doesn't seem to use any oil --I've topped it off with a half a quart in the past 4 months. (I know, that probably figures out to roughly a quart in 600 to 800 miles.) My problem occurs when I stop and back into my drive way -- I leave a trail of oil drips. I'm not sure why a rear main seal would appear to leak in reverse.
I'm just puzzled, not concerned. If I was concerned I'd just go old school and hang a lard pail under the rear main. (Recycling at its finest.)

Ray Rice, puzzled but not particularly concerned, in Rifton

[Patrick L.]

I'm thinking the driveway is not level.

[handlebar99]

Thanks Patrick, The driveway is uphill --so I'm backing uphill -- does that match your theory?

[Marshall V. Daut]

"I've topped it off with a half a quart in the past 4 months."
This tells me there's too much oil in the crankcase. Try to keep the oil level less than halfway between "L" and "F" on the dipstick to reduce the tendency for the rear main bearing too leak. If the level is too high, the primitive drainage system will be overtaxed right away and allow excess oil to follow the path of least resistance, i.e., exit through the rear main onto your driveway. The difference between the "F" and "L" marks on the Model A dipstick is only about 1/2 quart, so you will not be hurting your engine by lowering the oil level a little. Lots of guys have rear main bearing leaks and don't know it's likely because their oil level is too high. This is especially critical on steep hills, mountains and inclines, such as driveways, as "Patrick L." suggests.. If you are backing DOWN your driveway, the rear main slinger insert and drainage design will be overwhelmed.
Try dropping the oil level to a little above "L", allow recent oil leakage to abate, and then see if the oil still leaks in reverse. There is no logical other reason I can think of for oil to exit only in reverse. Only the gears inside the transmission make the conversion from forward to reverse, which dictate which way the pinion gear turns the ring gear.
Marshall

[Marshall V. Daut]

Oops! I see you answered Patrick's incline driveway question while I was still typing my answer.
Marshall

[Dave in MN]

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Interesting observation,
When the rear main drips, the oil is deposited inside the recess of the flywheel towards the engine. Normally, this oil is collected and held somewhat evenly around the perimeter by centrifugal force and is aided in its retention by the 3 degree slant of the engine.
When you drive, you are slowly filling the area I described above and if you exceed its capacity it overflows and goes out the drain hole while you are driving. You have not noticed this because you are moving.
When you back up your driveway, the oil flows forward from the flywheel (you have now eliminated the 3 degree slant) and drops to the flywheel housing and then out the drain hole at the bottom. Normal occurrence, I would say given what you are doing if the engine has a slow leak from the rear main.
Good Day!

[handlebar99]

Thanks, Dave, Your explanation sounds reasonable to me.

[29Cabriolet]

Originally Posted by handlebar99

I drive my roadster on average 50 miles per week -- trips to Lowes/Home Depot, ice cream, etc. runs fine, no problems. Doesn't seem to use any oil --I've topped it off with a half a quart in the past 4 months. (I know, that probably figures out to roughly a quart in 600 to 800 miles.) My problem occurs when I stop and back into my drive way -- I leave a trail of oil drips. I'm not sure why a rear main seal would appear to leak in reverse.
I'm just puzzled, not concerned. If I was concerned I'd just go old school and hang a lard pail under the rear main. (Recycling at its finest.)

Ray Rice, puzzled but not particularly concerned, in Rifton

OOOHHH! you mean reverse, like backing up reverse. I thought you had oil dripping from the driveway INTO the oil pan! (just kidding)

[C26Pinelake]

Consider installing a circular driveway so backing up will become unnecessary. Wayne

[Marshall V. Daut]

Dave in MN -
Excellent description and definition of what is going here - for MANY of us. Thank you for the clarification. We all know that Ford's Model A rear main drainage system was not one of mankind's better ideas since the dinosaurs died out. For the pre-WWII time when oil was cheap and no one cared about oil being wasted from the engine (witness engines of the era with criminally oil-wasting sleeve valve systems), this wasn't a problem. The poster's complaint would have been received in 1930 with either howls of derision or total complacency. Today, however, it IS a big deal. Your description of modern time rear main leakage problems is right on target.
I still suggest that too much oil in the crankcase is a contributing factor to many Model A owners' complaints about leakage - whether in forward or reverse motion. We may have an object example of this in practice here - no matter what the incline of his driveway may be. The problem just manifests itself more so while in reverse. 'Dunno why, but apparently it does.
Marshall