Logo
FULL SITE MENU

Oil on top of air filter

S

Smmm

New member
Okay. Just finished winterizing my 4.3 mercruiser engine in 1999 caravelle. When I took the air filter off, I notice there was some oil under the clamp that hold it in place. It was pretty clean oil. Not a lot but enough that it was visible. Is this normal or do I need to check into this. I did have to add some stern drive oil a couple time this year not sure if that would have anything to do with it or if that needs investigation as well. Any ideas?
 
Crankcase pressure (or blow-by as per the older days), is directed towards the flame arrestor. This is vaporous, and is likely what you are seeing.


.
 
I would be more concerned about the loss of oil from the outdrive than what has condensed on top of the Flame Arrestor...
 
makomark said:
I would be more concerned about the loss of oil from the outdrive than what has condensed on top of the Flame Arrestor...
Click to expand...

Okay. Last year we changed the outdrive oil. We noticed that the blue fiber washer on the drain screw was worn and in bad shape. We did not have a replacement so used it again. Never lost oil until then. I think it may just need a new washer (I hope that is) which I will do soon.... There is no sign of a leak. I think it is happening under pressure while on the lake.
 
Last edited:
You'll want to replace any fiber washers or any O-rings that have been installed once. Typically they won't go a second time around.

Here's what happens.
The drive starts out pretty much under ambient pressure (I.E., whatever the atmospheric pressure was at the time the plug was installed).

As your drive operates, the increase in temp causes an internal positive pressure.
If there is a leak, you may loose some oil.

The risky part comes into play as the drive cools.
When the drive cools, a negative pressure may now be created.
If there is/was a leak, the drive may now pull water back in as it wants to return to ambient pressure.

.
 
Okay. Thanks. Would you suggest draining and refilling or just changing out the washers. There is a reservoir tank and I do not see any signs of water... Not sure if there is a way to check for water...
 
Back
Top