Oil Breathers Uneven?

2007grabberGT

forum member
Joined
Apr 20, 2008
Posts
122
Reaction score
5
20190420_200236.jpg 20190420_200226.jpg Just curious. My oil breathers are vastly different in appearance after 2,800 miles.
Is this unusual, or just the nature of the beast?
Car has 57,000 miles and has had the Paxton on for 2,800 miles. Passenger side oil soaked, driver side clean and dry.
 

95ragtop

forum member
Joined
Sep 3, 2008
Posts
938
Reaction score
18
Location
Fayetteville, NC
There is a one way valve within the valve cover of the driver's side valve cover. This valve only allows air into the motor, not out. To remove it you need to pull off the valve cover and cut into it.
 

Dino Dino Bambino

I have a red car
Joined
Aug 11, 2014
Posts
3,880
Reaction score
1,751
Location
Cyprus
View attachment 69457 View attachment 69459 Just curious. My oil breathers are vastly different in appearance after 2,800 miles.
Is this unusual, or just the nature of the beast?
Car has 57,000 miles and has had the Paxton on for 2,800 miles. Passenger side oil soaked, driver side clean and dry.

'That's normal when you have a healthy engine with breathers on both valve covers. Just install a breather catch can on the passenger side so it'll collect all the crud and keep your valve cover clean. I made my own:

1 x 220g baking soda tin
1 x Scotch Brite scouring pad placed inside tin
1 x 3/8" valve cover breather filter
2 x 3/8" barbed fittings epoxied to lid of tin
1 x 3/8" vacuum hose
2 x small hose clamps

DIY_Oil_Catch_Can.JPG

Like you, I've capped off the intake manifold PCV port and have a valve cover breather on the driver's side, but that renders the breather virtually useless. As 95ragtop said, there's a PCV valve inside the driver's side valve cover and that only opens either if it's connected to the vacuum of the intake manifold, or if there's excessive blowby of combustion gases past the piston rings causing pressurization of the crankcase. If you have the latter, the breather filter will become oil soaked and that's bad news. Otherwise the PCV valve remains closed and the breather filter remains dry. In order to make the driver's side breather filter functional as a breather, you'd need to remove the valve cover and cut away the PCV valve.
 
Last edited:

JeremyH

3V Fuel Guru
S197 Team Member
Joined
Jan 10, 2009
Posts
20,857
Reaction score
197
Location
Virginia Beach
There is a one way valve within the valve cover of the driver's side valve cover. This valve only allows air into the motor, not out. To remove it you need to pull off the valve cover and cut into it.

This.

And the passenger side is a small about 5/16 outlet so all the venting is being done on that side so it will push more oil.

The driver side has much larger outlet about 5/8 but you need to remove the valve inside the cover to take advantage of it. Once both banks are vented properly you will push little to no oil into the breather itself. A oil cap breather helps alot as well as it's a huge opening to vent from.

I run 3 like I just mentioned with pcv valve removed and my breathers drip no oil and rarely need cleaned on a built motor pushing 16-18psi.

 

JeremyH

3V Fuel Guru
S197 Team Member
Joined
Jan 10, 2009
Posts
20,857
Reaction score
197
Location
Virginia Beach
Also if you search there are a few threads on the forum on how to remove the valve.
 

2007grabberGT

forum member
Joined
Apr 20, 2008
Posts
122
Reaction score
5
That's all great information from everyone. Thank you very much! I'll search into the PCV valve removal and put that project on the list for this spring. . . . Right after the Kooks install :D
 

Candy10

forum member
Joined
Dec 30, 2011
Posts
684
Reaction score
90
Location
Middle-of-Nowhere, Texas
This.

And the passenger side is a small about 5/16 outlet so all the venting is being done on that side so it will push more oil.

The driver side has much larger outlet about 5/8 but you need to remove the valve inside the cover to take advantage of it. Once both banks are vented properly you will push little to no oil into the breather itself. A oil cap breather helps alot as well as it's a huge opening to vent from.

I run 3 like I just mentioned with pcv valve removed and my breathers drip no oil and rarely need cleaned on a built motor pushing 16-18psi.

Can bad things come of using breathers on both sides, without removing that drivers side pcv valve? Besides the oil on the passenger breather?
 

Dino Dino Bambino

I have a red car
Joined
Aug 11, 2014
Posts
3,880
Reaction score
1,751
Location
Cyprus
It'll be fine as long as the passenger side breather doesn't get clogged up.
Jeremy H, the passenger side is 3/8".
 

GriffX

Member
Joined
Sep 28, 2017
Posts
496
Reaction score
158
Correct me if I'm wrong:
I don't think its a good idea to use these caps.
First, a vacuum in the engine helps to minimize internal power loss (air pump loss)
Second, the engine has an active ventilation system, fresh air is going in on the passenger side and out on the driver side; the intake produces vacuum and sucks the fresh air with the blow by gases out. The fresh air prevents the oil from thinning and sludge from fuel and water.
I use a catch can on the driver side instead.
 

2007grabberGT

forum member
Joined
Apr 20, 2008
Posts
122
Reaction score
5
If I thought it was a bad idea it wouldn't have gone this route. I still MAY go to a catch can. The debate over breathers vs catch cans has been covered in several really detailed threads here. After I read them, I decided for my particular application the breathers would work. I previously had detonation problems before i went forced induction and i wanted to ensure zero oil vapor was making it into my intake and effecting octane. The price I pay is more frequent oil change intervals, but I average 1,000 miles per year and that was a compromise I was willing to make.
What catch can are you running? How much are you catching? It may be easier for me to switch to a catch can than remove the cam cover and get that pcv valve out of there....:biggrin:
 

1950StangJump$

forum member
Joined
Apr 1, 2010
Posts
966
Reaction score
108
I'm confused.

On my Kenne Bell 4.6, the oil catch can is on the DRIVER'S side. It catches a fair amount of blowby. The passenger side is a straight tube that runs right to the air intake and is squeaky clean.

I know it was the opposite on a Coyote. But, why the opposite with the OP's 4.6, i.e. that his oil seems to be coming out the opposite side?
 

Candy10

forum member
Joined
Dec 30, 2011
Posts
684
Reaction score
90
Location
Middle-of-Nowhere, Texas
I'm confused.

On my Kenne Bell 4.6, the oil catch can is on the DRIVER'S side. It catches a fair amount of blowby. The passenger side is a straight tube that runs right to the air intake and is squeaky clean.

I know it was the opposite on a Coyote. But, why the opposite with the OP's 4.6, i.e. that his oil seems to be coming out the opposite side?

Interesting, i’ve got a 2010 4.6 with KB, breathers on both sides. Driver side is clean as the day i got it, passenger side needs cleaned up from time to time.
 

1950StangJump$

forum member
Joined
Apr 1, 2010
Posts
966
Reaction score
108
Interesting, i’ve got a 2010 4.6 with KB, breathers on both sides. Driver side is clean as the day i got it, passenger side needs cleaned up from time to time.

Maybe the difference is breather vs. catch can?

The crappy little catch can that comes in the KB kit was on the driver's side when I bought it, and I quickly changed it out for a Moroso because the small KB catch can filled up so quickly.

Like I said, I get a good amount of oil from the Moroso, and the passenger side is completely clean. I was under the impression that all 4.6s were this way.
 

Dino Dino Bambino

I have a red car
Joined
Aug 11, 2014
Posts
3,880
Reaction score
1,751
Location
Cyprus
Maybe the difference is breather vs. catch can?

The difference is whether the positive crankcase ventilation (PCV) valve in the driver's side valve cover (VC) remains active or not depending on the crankcase ventilation set-up.
If you only have a breather filter on the driver's side, there's no vacuum to open the PCV valve so it always remains closed. This means that the crankcase now has to ventilate on the passenger side, and that's why you either need another breather on the passenger side (which gets dirty more quickly), or a catch can breather like I have (which keeps the filter clean).
If you have a catch can on the driver's side VC that's connected to the intake manifold vacuum port, the PCV valve will open under that vacuum and vent oil vapors from the driver's side. In that situation, you cannot run a breather or a catch can breather on the passenger side as it would effectively cause a large vacuum leak with unmetered air entering the intake manifold. You must run either a regular catch can on the passenger side or a straight pipe from the intake elbow to the passenger side VC.
 

1950StangJump$

forum member
Joined
Apr 1, 2010
Posts
966
Reaction score
108
The difference is whether the positive crankcase ventilation (PCV) valve in the driver's side valve cover (VC) remains active or not depending on the crankcase ventilation set-up.
If you only have a breather filter on the driver's side, there's no vacuum to open the PCV valve so it always remains closed. This means that the crankcase now has to ventilate on the passenger side, and that's why you either need another breather on the passenger side (which gets dirty more quickly), or a catch can breather like I have (which keeps the filter clean).
If you have a catch can on the driver's side VC that's connected to the intake manifold vacuum port, the PCV valve will open under that vacuum and vent oil vapors from the driver's side. In that situation, you cannot run a breather or a catch can breather on the passenger side as it would effectively cause a large vacuum leak with unmetered air entering the intake manifold. You must run either a regular catch can on the passenger side or a straight pipe from the intake elbow to the passenger side VC.

Kick ass explanation. Thanks. I always thought the driver's side was the only way.

EDIT: From everything I can tell, if you run a catch can on the driver's side, putting a catch can on the passengers side would be a complete waste. At least on mine, zero oil comes out of it.
 

JeremyH

3V Fuel Guru
S197 Team Member
Joined
Jan 10, 2009
Posts
20,857
Reaction score
197
Location
Virginia Beach
Kick ass explanation. Thanks. I always thought the driver's side was the only way.

EDIT: From everything I can tell, if you run a catch can on the driver's side, putting a catch can on the passengers side would be a complete waste. At least on mine, zero oil comes out of it.

Indeed, because air is drawn in the passenger side from the intake tube or breather if installed when the driver side is a "closed" setup the pcv valve opens for a short period under vac transitions in the manifold.

It's a bit of a double edge sword, yes it appears to function "good" because you catch a bunch of oil but it's because the situation to force more oil out that side is also created.

People often associate catching more oil with good/better crankcase ventilation but that's not exactly the case. The more freely the pressure is relieved or prevented from ever building up the less oil you will push out and need to catch.

Simple way to look at it is when you make a setup that vents blowby and windage really well, the oil stays in the crankcase where it belongs and then you just catch hot vapors and moisture etc that condenses in the can.
 
Last edited:

JeremyH

3V Fuel Guru
S197 Team Member
Joined
Jan 10, 2009
Posts
20,857
Reaction score
197
Location
Virginia Beach
I am a big fan of the cfm oil cap breather. It can be used in which ever you prefer, (open or closed systems) and is a very large opening to relieve pressure from. I would wager you would see alot less oil collected in that driver side can by adding one.

When my setup was just 2 breathers on each cover and the pcv valve was still installed the passenger side would soak with oil and drip and I would get oil leaking at the vct solenoid grommets. After adding the oil cap breather and removing the driver pcv. None of the breather soak with oil or drip and the grommets no longer leak. It would same concept if I was running hoses to a can. And why guys install larger fittings and lines on their covers. The better you vent the less oil you force out.
 

JeremyH

3V Fuel Guru
S197 Team Member
Joined
Jan 10, 2009
Posts
20,857
Reaction score
197
Location
Virginia Beach
"CFM Performance valve cover breathers are the best money can buy and is the reason they have become extremely popular so quickly. They are so much more than a pretty filter on top of your valve cover and offer features that no other kits offer.

It is the only breather on the market which incorporates a check ball to keep unmetered air from coming through while the PCV system is active and the crankcase is under vacuum. In other words, this breather works just like a factory oil cap under normal driving conditions but will vent any positive crankcase pressure present under full or part throttle. It is also the only breather with an integrated baffle to help contain oil particles in the engine rather than allowing them to exit the valve cover and saturate the filter element. Filter tops are available in several popular powdercoat finishes, chrome, hydrocarbon and select OEM colors."

https://www.c-f-m.com/performanceparts/pc/Valve-Cover-Breathers-c744.htm
 

JeremyH

3V Fuel Guru
S197 Team Member
Joined
Jan 10, 2009
Posts
20,857
Reaction score
197
Location
Virginia Beach
I highlighted in bold the key feature. It keeps crankcase pressure from building up when theres boost in the manifold. When the line from manifold to driver side valve cover is connected the pcv cant open as boost pressure in the manifold is stronger and keeps it shut. So instead a boosted car is effectively building pressure in the crankcase as the smaller passenger side fitting is not adequate to vent the increased blowby pressure. Then when you let off the throttle and have a transition back to vac in the manifold the pcv opens briefly and you have a big rush out and through your can which tends to push more oil out.
 
Last edited:

Candy10

forum member
Joined
Dec 30, 2011
Posts
684
Reaction score
90
Location
Middle-of-Nowhere, Texas
I highlighted in bold the key feature. It keeps crankcase pressure from building up when theres boost in the manifold. When the line from manifold to driver side valve cover is connected the pcv cant open as boost pressure in the manifold is stronger and keeps it shut. So instead a boosted car is effectively building pressure in the crankcase as the smaller passenger side fitting is not adequate to vent the increased blowby pressure. Then when you let off the throttle and have a transition back to vac in the manifold the pcv opens briefly and you have a big rush out and through your can which tends to push more oil out.

I would love to run their oil cap breather, but my intake tube runs passenger side right over the cap.
 

Support us!

Support Us - Become A Supporting Member Today!

Click Here For Details

Sponsor Links

Banner image
Back
Top