Ford Lehman Sump Breather?

Oil Gypsy · Jan 24, 2022

Hello,

On the left hand side of the sump, in front of the dipstick on my FL120 there is a fitting that Ive largely ignored since owning the boat. Today I unscrewed it to see what it is, the top is bolted on and has a wire mesh filter attached on the underside, while removing it the drum started to revolve and has an oil level mark stamped on the outside, the basin was pretty full of black congealed waste, no oil. The top of the drum it says refer to the owners handbook but my operations manual doesn't mention this fitting.

Im assuming that it is some sort of breather and that the "Well" should be full of engine oil, can anyone confirm this please.

C lectric · Jan 24, 2022

You don;t show where the thing actually sits on the engine.

This cap would appear to be the vent to the atmosphere. The wire thread packing is meant to catch the oil in the vapours or most of it.
The cup is the catch basin and is only intended to catch that oil so should be empty when you have cleaned the vent up.

And this is where a referral to Brian at American Diesel will come in. He is now the expert on these engines. THe odds are good there is a better way to deal with crankcase fumes/vapours and he will likely know of it.

Google his shop and call or email him.

SteveK · Jan 25, 2022

I wondered about that too, oil pan vent. add/withdraw air from the sump to compensate for oil levels?
There is also a valve cover vent going into the breather. I thought about routing the valve vent into it and recycle oil fumes.

C lectric · Jan 25, 2022

Soo-Valley said:
I wondered about that too, oil pan vent. add/withdraw air from the sump to compensate for oil levels?
/QUOTE]

Yes, the vent will do that too. As the oil heats, cools and the engine pumps oil throughout the system the pan level will change.

But the main function is to strip oil from the blowby fumes which would otherwise spread all over the engine compartment making a big mess and sometimes foul the air in the cabins.

Newer engines have a fully functional crankcase venting system which leads those fumes back to the engine intake so they are burned in the combustion chambers.

Cleaner atmosphere and less smell and mess aboard.

My different engine, 1976, had a similar system for catching oil out of the fumes.

I altered that so the fumes are all lead back to the the engine intakes for the fumes to be burned. No more smell unless I forget to reconnect the hoses after doing some service work.

All engines, even brand new ones, produce blowby. THe question is how much.

Oil Gypsy · Jan 25, 2022

I spoke to Brian at American Diesel this morning, the breather was only fitted to the early models of the Leham engine that were marinised in Asia in the early 1970's. The "well" is supposed to be full of oil so that the wire mesh is immersed in a bath of oil.

Apparently it was found that this style of breather could cause back pressure in the crankcase and the breather wasn't installed on later models, also as mentioned fumes from the crankcase could vent to the engine space and bilges which is far from ideal. There is an alternate system in the engine to vent the crankcase to the foam covered air inlet on the engine where the fumes are fed to the pistons and emitted through the exhaust after combustion.

The recommendation is that the unit be removed and the hole be plugged.

rgano · Jan 25, 2022

I plugged both of mine many years ago with a red plastic plumbing plug from the big box store.

Ford Lehman Sump Breather?

Oil Gypsy

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