Finally Jumped on the Oil Catch Can Bandwagon

[iamdub]

So what happens if you don't empty it out when it is full? I hesitate to add more stuff to have to check (i.e. nag my husband to check haha). I can certainly do the "normal" vehicle checks like fluid levels etc, but not sure about the catch can. Will it overflow, or just stop "catching"? Would it cause more harm than good if it was not emptied when full?

If it fills up, the vacuum side will start to suck the oil like a Shop Vac hose in water. It'd be about the same as not having a can in the first place. You shouldn't have to drain it any more than once every oil change. If your engine is passing as much oil as Jason's, then you need to address the problem. The catch can isn't a fix, it's a supplementary to the proper fix(es).

This is why I always recommend the updated rocker cover first. It keeps the oil inside the engine where you don't have to do anything, rather than letting the oil escape the engine through the PCV system where you have to catch it in the can, then drain it. The updated cover isn't 100% effective since oil particles are still present in the crankcase air and THAT is what the catch can is supposed to be filtering out.

 

[iamdub]

Just get a larger capacity one if worried about it.

I mounted mine up near the front on drivers side, behind the washer fluid reservoir and over the spare battery tray. It make it easily accessible plus I can set a small empty butter tub or cup under it when draining and don't have to stand there holding it.

Mine's a 2012 and came with the updated pcv valve cover and I drain mine at an oil change and halfway between oil changes, so about every 2500 miles, and I only get about a shot glass worth out of it, so I could probably go with only draining it at every oil change.

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Mine consistently drains 3 oz at every 5,000-mile OCI, so that's the same as yours. Mine came with the updated cover and I disabled AFM about a year after I bought it.

 

[Jason in DLH]

Good lawd! You at least need the updated rocker cover. I'd do the upper engine cleaning TSB since your engine has been burning so much.

Agreed! I’ll be changing that once I dig into changing the Valley Pan Gasket. Probably sometime in the summer.

 

[iamdub]

That is the way I have always understood why the AFM pressure relief valve was there. What I never got was why high RPM operation caused that valve to spray oil. To me, the pressure spiking when the solenoids closed (when the system was moving from V4 to V8 mode) made sense, as, like you said, shutting the oil flowing to the eight AFM lifters must create some sort of pressure spike. But that isn't happening during extended high RPM operation (like when I was towing the big old trailer in trailer mode all those years).

I think I am still really puzzled about that AFM relief valve and when it is normally open.

It's not normally open. It's a pop-off style valve, which has a very narrow opening and closing range. The one in the oil pump is much more linear- it opens gradually the higher the pressure gets. When the valve opens, it's a sudden ~55 psi of oil at X volume blasting out of the valve's tiny orifices. This is what makes it spray.

LS engines consume more during high RPM usage just from their strong PCV currents. Lots of air into the crankcase leads to lots of air out of it. Also, if you had the older rocker cover back then, that'd really contribute to the consumption. The baffle hole was in line with a rocker, so drops of oil would get flicked into it as the rocker splashed it. Higher RPM means higher oil pressure, which means that oil spurting from the push rod hole would turn into a stream, steadily shooting into that hole.

 

[Rocket Man]

It's not normally open. It's a pop-off style valve, which has a very narrow opening and closing range. The one in the oil pump is much more linear- it opens gradually the higher the pressure gets. When the valve opens, it's a sudden ~55 psi of oil at X volume blasting out of the valve's tiny orifices. This is what makes it spray.

LS engines consume more during high RPM usage just from their strong PCV currents. Lots of air into the crankcase leads to lots of air out of it. Also, if you had the older rocker cover back then, that'd really contribute to the consumption. The baffle hole was in line with a rocker, so drops of oil would get flicked into it as the rocker splashed it. Higher RPM means higher oil pressure, which means that oil spurting from the push rod hole would turn into a stream, steadily shooting into that hole.

Excellent explanation. A+. Gold star and everything. Thank you! I don’t even have one of those motors but I always wondered about that valve. That makes sense.

 

[iamdub]

Excellent explanation. A+. Gold star and everything. Thank you! I don’t even have one of those motors but I always wondered about that valve. That makes sense.

Well, when you swap in that built 6.3, it still won't be a problem cuz you'll plug off the port in the pan.

 

[iamdub]

Hey [emoji870]
Yes looks like I could make that,already have some gasket sheet handy. The holes look like they might be around 3/8 as well. I have a countersink bit around 13-14 mm
Sorry 1/2 9/16 [emoji6] lol (cheeky) I am old so imperial has been part of my life before we went metric.[emoji69] haha
I had a look at the catch cans. Pretty cheap. I like the red one [emoji106]
If I was to breath both rocker covers into a breather can would I be able to cap the intake near the throttle body and on the manifold without any problems or does there need to be connection through these things?
Lots of questions, hope they make sense.
Thanks [emoji111]

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I'll measure the holes just so you'll have a reference.

I'm not so sure about having both covers breathe into a singe catch can because I don't know for sure how the flow is set up. Since one side has a PCV valve on it, this tells me that it's like an LS with one side being the inlet and the other being the outlet. I'd put the catch can on the side with the PCV valve.

 

[Jason in DLH]

Also, if you had the older rocker cover back then, that'd really contribute to the consumption. The baffle hole was in line with a rocker, so drops of oil would get flicked into it as the rocker splashed it. Higher RPM means higher oil pressure, which means that oil spurting from the push rod hole would turn into a stream, steadily shooting into that hole.

I was just going to ask why the new design valve cover decreases oil consumption, but you beat me to it and makes total sense now!

 

[iamdub]

I was just going to ask why the new design valve cover decreases oil consumption, but you beat me to it and makes total sense now!

View attachment 274374

A blatant derp moment from the General.

 

[wsteele]

It's not normally open. It's a pop-off style valve, which has a very narrow opening and closing range. The one in the oil pump is much more linear- it opens gradually the higher the pressure gets. When the valve opens, it's a sudden ~55 psi of oil at X volume blasting out of the valve's tiny orifices. This is what makes it spray.

LS engines consume more during high RPM usage just from their strong PCV currents. Lots of air into the crankcase leads to lots of air out of it. Also, if you had the older rocker cover back then, that'd really contribute to the consumption. The baffle hole was in line with a rocker, so drops of oil would get flicked into it as the rocker splashed it. Higher RPM means higher oil pressure, which means that oil spurting from the push rod hole would turn into a stream, steadily shooting into that hole.

I understood the spray from the holes in the AFM relief valve squirting out horizontally into the bottom of the block and I also got the way the down rev valve cover got so much oil into the channel leading to the PCV and ultimately into the intake.

What puzzled me, and still puzzles me I guess to some degree, is the “when”. Is it open and spraying all the time the engine is in the higher RPM range, if the oil pressure is above 55 PSI? I suspect it does, regardless of the status of the AFM solenoids.

I frankly never really focused on my OP when in tow mode hauling up some of those big inclines (if I fixated on anything, it probably was the transmission temp) but given the fact that my engine always seemed strong in the OP area and the first 60K or so miles of driving was with a big old tandem axle enclosed trailer in tow, I guess maybe my AFM pressure relief valve was spraying a great deal of the time (versus just when coming out of V4 mode).

I think maybe what really convinced me my stuck oil rings were from oil ingested from the PCV was when I saw the spark plug in number 7, when the first diagnosis was started on my oil consumption. It just made squirts from the AFM relief valve shooting a brief squirt up into the bottom of the cylinder bore seem unlikely to be the source of the stuck rings.

Thinking about a steady 55+ PSI stream of oil from that AFM relief valve up into the bottom of a cylinder bore inline with the jet, makes believing the AFM deflector might actually have done something in the grand scheme of things.

I suspect I will actually never know for sure.