Don't drain your oil catch can into the crank case

[A.J.]

I had to remove my oil catch can today to install a vacuum bleed valve. So I took it apart to give it a good cleaning. I had just done an oil change last week and drained it. Some of the stuff in it was so thick it wouldn't come out of the drain pet ----. I took some pictures for those that think draining the catch can back into the crankcase is a good idea.

The top. This is where the pcv valve pulls vacuum and vents to the air box.


This wouldn't drain out.




Cleaned.


The inside of the bottom. The barb on the bottom goes to the valve cover.




A.J.

[Vigo]

naaaaaasty. Good advice.

[Big_P]

Wow, never woulda' imagined that. Thanks for posting!

[Force Fed Mopar]

Nothing like some good ol' condensation

[rbryant]

It seems that the water vapor that normally goes out the PCV and into the intake and is "burned" with the charge in the stock system simply accumulates in a closed loop when you add a catch can this way.

Separating both the oil and the water into the can makes sludge.

The oil is lighter than the water so a simple catch can won't be able to keep the oil in the can and allow the water to go into the air charge. Either you catch both the oil and the water or you catch nothing.

Draining the catch can into the pan actually makes the sludge worse than in the stock setup because it doesn't allow the water to leave the system into the intake charge.

I agree that draining that sludge back into the pan isn't good.

-Rich

[puppet]

I think somebody has a head gasket issue. That's "more than normal" condensate for the time you've had since the last oil change ... unless you've never been inside the can for a year or two? Does the underside of your oil cap look like that?

[rbryant]

I think somebody has a head gasket issue. That's "more than normal" condensate for the time you've had since the last oil change ... unless you've never been inside the can for a year or two? Does the underside of your oil cap look like that?

I doubt that is a headgasket issue. Lots of SRT4 guys get more than that in 10k miles. TurboShad had a FULL can recently and IIRC the gunk looked about the same.

-Rich

[shadow88]

Short drives much? I doubt you live in a cold climate. Could it be a low spot in your pcv tube where the condensation collects?

[DodgeZ]

The factory drains back in to the oil pan.

[shadow88]

The factory drains back in to the oil pan.

Through where?

[cordes]

Through where?

Some of the later cars drained back through the turbo oil return.

[shadow88]

Some of the later cars drained back through the turbo oil return.

Do you know what year that started? This is the first I ever heard of it.

[DodgeZ]

I want to say 90 was the first year but it may be 91

[rbryant]

I want to say 90 was the first year but it may be 91

But unless you count the 95 Neon they didn't have a real oil separator did they?

Without something to collect the water/oil and prevent it from burning off they are probably just draining big oil burps and letting the rest go into the intake. They probably just wanted a place for the oil to go when it got excessive instead of dripping it on the ground.

-Rich

[22shelby]

True Z however alot of the condisation comes from the can itself... ive noticed this in the shop car granted its a dry sump system but if the car has been sitting, weve noticed a good amount of water on the inside top side of the can....

condensation will happen in any metal external storage container esp alum ones.... weve noticed it happens more on cooler days so weve come to the conclusion that the warm vapor of the motor going into the cool alum can will cause condensation...

keep draining it maybe a lil more often or you can try a plastic Moroso catch can, theres is prretty trick w/ the lil filter on the top...

[johnl]

Water vapor is pulled into the engine when it cools, just like water vapor is pulled into the exhaust system when it cools.

That's why mufflers rust out and that's why there's water in the catch can. The catch can is a place outside of the engine where the engine vapors get cool enough for the water to condense. It gets stuck there, taken out of the loop.

The slight amount of water in the air that is pulled into the engine when it cools is not good, its not too bad either. The water can't do much damage in a vehicle that is driven often because everything inside the engine is saturated with oil and when the engine cools the water just condenses out of the air and settles to the bottom of the pan. Later, when the engine is again brought up to temperature, the water is vaporized and then burnt when, and if, it passes through the pcv system.

[DodgeZ]

But unless you count the 95 Neon they didn't have a real oil separator did they?

Without something to collect the water/oil and prevent it from burning off they are probably just draining big oil burps and letting the rest go into the intake. They probably just wanted a place for the oil to go when it got excessive instead of dripping it on the ground.

-Rich

In the later years the airbox is basically a catch can that auto drains itself. It sucks air through and any oil build up goes back in to the motor instead of getting in the intake plumbing.

[rbryant]

In the later years the airbox is basically a catch can that auto drains itself. It sucks air through and any oil build up goes back in to the motor instead of getting in the intake plumbing.

I will have to look more carefully at the later airboxes but most of them that I have looked at don't separate much compared to a baffled catch can. They would catch a little bit of oil when under boost with bad blowby but in normal operation most of the oil and water would still go into the intake. The baffled catch cans catch a lot more and therefore more water would return to the pan instead of going into the intake.

-Rich

[A.J.]

I think somebody has a head gasket issue. That's "more than normal" condensate for the time you've had since the last oil change ... unless you've never been inside the can for a year or two? Does the underside of your oil cap look like that?

I don't have a head gasket issue. If that was on my dip stick and not in the catch can I would agree with you. Don't forget, what I took a picture of WOULDN'T drain out. When I do an oil change, while the oil is draining, I drain the catch can. My oil cap is clean. I've seen many cars with condensation built up under the cap and not have a blown head gasket.

Short drives much? I doubt you live in a cold climate. Could it be a low spot in your pcv tube where the condensation collects?

You are correct! I drive 3.5 miles to work and in the mornings it has been in the 30's the past couple of weeks. In the afternoon/evenings it's been in the 50's and low 60's.

A.J.

[DodgeZ]

I will have to look more carefully at the later airboxes but most of them that I have looked at don't separate much compared to a baffled catch can. They would catch a little bit of oil when under boost with bad blowby but in normal operation most of the oil and water would still go into the intake. The baffled catch cans catch a lot more and therefore more water would return to the pan instead of going into the intake.

-Rich

Whatever dude. Maybe you should make an excel spreadsheet to show the oil water ratio that will get sucked in the motor. The catch can sludge is a by product of the catch can. Motors build up moisture and burn it off during normal use with the help of the pcv. If you don't have a catch can the tube going from the pcv to the intake doesn't get all sludged up. If you have a catch can in between your pcv and the intake with a drain on the bottom of it going back to the motor it isn't going to give you any issues. The catch can sitting there with oil in it and condensation of course is going to get nasty. There is nothing heating up the catch can to vaporize the water and I'd guess ghAyJ doesn't connect the catch can to the intake.