A question about oil cooler positioning / placement.

If an oil cooler is placed somewhat higher than the sump/oil pan will
there be any issue with
oil draining back into the sump.

One of the machines currently under construction here the want is  to
place the oil cooler
vertically the fittings would be one at the top and one at the bottom Is
there likely to be an
issue with the oil draining back into the sump?

If there is an issue with drain back we'll need to fit one way valve/s
to stop this occurring I guess

What do you think?

Regards David

The oil cooler is under pressure so where it is plumbed back into the sump
should be of no consequence.

If the engine is stopped for a long time I think the oil is going to drain
out of the engine anyway so there will be a period of time where
the bearings get no oil. To forestall this people use pre oilers
which consist of a high pressure electric pump.