Water in oil catch tank

[Mucus72]

Hi all,

When I checked fluids prior to a track day at the weekend, I noticed that the oil catch tank (420R dry sump variant) had around 50ml of liquid in the bottom, all of which was mayonnaise like in nature, but more water than oil.

I checked my coolant and all pink with no oil. Checked the oil tank itself and the oil looked OK, but there was slight milky residue on the underside of the cap, which is a long way above the oil level.

I cleaned out and dried the catch tank, wiped the oil tank cap dry and went for the track day.

I checked the catch tank after the track day and I have water in it again, around 15ml, but no oil. And the water is clear. In fact the water content in the previous mayonnaise was clear too.

And the car was trailered to the track on a cold, dry day, and the track day was dry.

So I guess that conditions with heat and moisture (from somewhere) is enough to find steam in the oil tank tha condenses and runs down the upper tube into the catch tank?

Is this normal? My car is kept in a dry garage, attached to our house, no damp, new house.

I would appreciate some thoughts?

[JNC]

It's condensation it's normal my 220 D is the same.

[Nigel R300]

It's a mixture of oil droplets ,water vapour and unburnt fuel 

[oilyhands]

The main by products of combustion are CO2 and H2O, so you would expect crankcase fumes to comprise of the same, together with some oil mist. The water vapour and ool will often emulsifying. So dont worry unduly.

Oily

[Mucus72]

Thank you, all three of you, for setting my mind at ease. As someone who doesn't understand the finer points of engines, I'm now wondering where does this water go in a closed system, and in that scenario, why doesn't it slowly turn all of the oil to mayonnaise as it condenses and trickles down into a wet sump?

[7 wonders of the world]

A closed system relates to the engine being non vented itself, however the DS tank is still vented to atmosphere in the same way yours is either tro a straight breather or via a catch tank.

[oilyhands]

It's a lot hotter in the engine cavity so the water doesn't condense,any that does when the engine is cool is soon burned off as it heats up. In a PCV system it is drawn into the inlet manifold and is passed through the engjne, in a vented system it ends up in the catch tank.

Oily

 

 

[JNC]

Before mine was upgraded it use to vent into the air filter box then sucked into the engine again 

[Mucus72]

This is why I love BlatChat. I've learnt so much over the years, thanks again guys!

Marcus