E85 + catch can = lots of water

The above picture was after about 60 mile run.
I emptied it cleaned the can, took it out again for another 50 mile (+/- a few miles) drive and had about the same amount water in the can.


The Engine Whisperer
The primary products of combustion are water and CO2. Gasoline and diesel also make water when they combust.
That water (vapor) goes out your tail pipe and past your rings into your crankcase.
Routing your blow-by to a cool place away from the engine allows that water to condense into a liquid and accumulate.
So.... it’s perfectly normal.

When it warms up around here and your under hood temps increase, you won’t see nearly as much water accumulating.
are you venting to atmosphere or sealed type can ?
curious as to how most are running them. I put one on routing both valvecovers and the pcv to a can vented to atmosphere, nothing routes back into the intake


You're very kind. Some day it will get you killed.
A pcv has to coonected to a vacuum source to suck out the fumes in the crankcase. If it just goes to a vented catch can it's not doing anything. Fresh air goes in through vc vents or as a closed system fom the intake pipe pre turbo to the vc and is removed by vacuum via the pcv. A catch can in that line is for condensation and oil fumes to collect in. During boost the pcv /check valve closes off the crankcase. Fumes are vented via vc on an open system. On a closed system lines would come from the vc and go to the intake pre turbo to be run through the engine. A catch can is sometimes done on those lines.

Chuck Leeper

Waay too old!
Staff member
There is a discussion, as to how a can should be installed.
The MM PCV system, has a check valve in the breather, on the top of the can, and a hi q PCV valve screwed into the side of the can.
The link has instructions, and a description of how it works.