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.

 

[Jason in DLH]

while using all my mental power in trying to understand all of this (and reading another thread) I just realized I’ve been listening to the same song on repeat for the past half hour.

 

[wsteele]

while using all my mental power in trying to understand all of this (and reading another thread) I just realized I’ve been listening to the same song on repeat for the past half hour.

Sorry if I muddled the picture as far as how these engines get to start flowing oil out the PCV.

I have always tried to understand what role the AFM PR Valve played in how my rings got stuck, and I think I probably will never know with any certainty.

When I reflect on the input from @iamdub and @donjetman and their experiences, along with my own experience with my stuck rings, a few things seem to rise to the top.

The best thing anyone with a pre 2012 version of one of these trucks can do is assure they have the proper updated drivers side valve cover for their model year (the TSB says they are different for 2007-2008 and 2009-2010 and looking at Rock Auto they do indeed list two different valve covers for those model years).

The next best thing then is to install a catch can so you can know exactly how much oil your engine is trying to put back into the intake.

It is hard to let thinking about that Pressure Relief Valve go, but I think I have to, as it just is going to bug me for no good purpose.

 

[gooffeyguy]

A blatant derp moment from the General.

Surprised it took GM that long in this generation to realize this. Valve covers have had baffeld pcv/oil fill ports since forever to keep the spray from the pushrods/rockers out

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[Jason in DLH]

Sorry if I muddled the picture as far as how these engines get to start flowing oil out the PCV.

I have always tried to understand what role the AFM PR Valve played in how my rings got stuck, and I think I probably will never know with any certainty.

When I reflect on the input from @iamdub and @donjetman and their experiences, along with my own experience with my stuck rings, a few things seem to rise to the top.

The best thing anyone with a pre 2012 version of one of these trucks can do is assure they have the proper updated drivers side valve cover for their model year (the TSB says they are different for 2007-2008 and 2009-2010 and looking at Rock Auto they do indeed list two different valve covers for those model years).

The next best thing then is to install a catch can so you can know exactly how much oil your engine is trying to put back into the intake.

It is hard to let thinking about that Pressure Relief Valve go, but I think I have to, as it just is going to bug me for no good purpose.

It’s all making more sense now that I got some sleep.

Your right about the different P/N’s for the different years...

2007 - 2008: 12570427
2009 - 2011: 12642655

 

[Sparksalot]

There’s been mention of baffling above. How much baffle, steel wool, whatever, is needed?

 

[Caligirl]

Sorry if I muddled the picture as far as how these engines get to start flowing oil out the PCV.

I have always tried to understand what role the AFM PR Valve played in how my rings got stuck, and I think I probably will never know with any certainty.

When I reflect on the input from @iamdub and @donjetman and their experiences, along with my own experience with my stuck rings, a few things seem to rise to the top.

The best thing anyone with a pre 2012 version of one of these trucks can do is assure they have the proper updated drivers side valve cover for their model year (the TSB says they are different for 2007-2008 and 2009-2010 and looking at Rock Auto they do indeed list two different valve covers for those model years).

The next best thing then is to install a catch can so you can know exactly how much oil your engine is trying to put back into the intake.

It is hard to let thinking about that Pressure Relief Valve go, but I think I have to, as it just is going to bug me for no good purpose.

So based on this thread, if I understand it correctly, since I don't know if my Tahoe has the new valve cover, putting in the catch can MAY help me alleviate some of the damage if it's the old one and/or determine if it is (besides taking it off to look-wish they put something on the new ones that is identifiable without taking it apart).

Or do folks who have done the AFM delete/new valve cover STILL get oil/gunk in the can and I won't know from a catch can's contents?

Wish I had more experience with actual work under the hood- I'd take it apart just to look (and replace if needed) even though I'm not showing any signs now at 88k.

Drives my husband nuts thinking I'm borrowing trouble for tomorrow and I prefer to think of it as "prevention-minded" or "forward-thinking". Besides, you'd think the idea that I could tell him "I told you so" if we ever had issues would be enough incentive for him to do it for me now haha

I'm with you and if I ever had issues, it will drive me nuts with the wanting to know if ABC caused XYZ.

 

[Jason in DLH]

There’s been mention of baffling above. How much baffle, steel wool, whatever, is needed?

I believe most cans use filters in them that will work. I did check my JLT and it does have a filter on the outlet side which appears to be working well with the amount of crud I caught during only a 20 minute drive.

Here’s a great video about the different types catch cans (with data showing they actually work)...

 

[Jason in DLH]

So based on this thread, if I understand it correctly, since I don't know if my Tahoe has the new valve cover, putting in the catch can MAY help me alleviate some of the damage if it's the old one and/or determine if it is (besides taking it off to look-wish they put something on the new ones that is identifiable without taking it apart).

Or do folks who have done the AFM delete/new valve cover STILL get oil/gunk in the can and I won't know from a catch can's contents?

Wish I had more experience with actual work under the hood- I'd take it apart just to look (and replace if needed) even though I'm not showing any signs now at 88k.

Drives my husband nuts thinking I'm borrowing trouble for tomorrow and I prefer to think of it as "prevention-minded" or "forward-thinking". Besides, you'd think the idea that I could tell him "I told you so" if we ever had issues would be enough incentive for him to do it for me now haha

I'm with you and if I ever had issues, it will drive me nuts with the wanting to know if ABC caused XYZ.

After doing lots of recent research on this catch can business, I’ll be installing one in all vehicles I own from now on. It’s a great preventative maintenance device and piece of mind that oil isn’t being reintroduced into the intake manifold. In my opinion.

 

[wsteele]

So based on this thread, if I understand it correctly, since I don't know if my Tahoe has the new valve cover, putting in the catch can MAY help me alleviate some of the damage if it's the old one and/or determine if it is (besides taking it off to look-wish they put something on the new ones that is identifiable without taking it apart).

Or do folks who have done the AFM delete/new valve cover STILL get oil/gunk in the can and I won't know from a catch can's contents?

Wish I had more experience with actual work under the hood- I'd take it apart just to look (and replace if needed) even though I'm not showing any signs now at 88k.

Drives my husband nuts thinking I'm borrowing trouble for tomorrow and I prefer to think of it as "prevention-minded" or "forward-thinking". Besides, you'd think the idea that I could tell him "I told you so" if we ever had issues would be enough incentive for him to do it for me now haha

I'm with you and if I ever had issues, it will drive me nuts with the wanting to know if ABC caused XYZ.

I don't think there is a way to tell which valve cover you have unless you pull it off and look at the underside of the casting.

If I recall from a previous thread, you may have posted that your engine is not using any oil at all between changes (I could have that completely wrong and thinking about somebody else). If that is the case, the urgency on any of this stuff definitely gets into the "preventive" mode, versus "fixing" mode.

My belief now is a catch can is a great device for insight into what is going on inside. On an engine that uses oil, it will tell you if you are pumping it out the PCV and back into the intake, which in measurable quantities is not good for anything. If you see large quantities, you know you need to at least get that valve cover pulled and check to see what part number you have.

 

[wsteele]

There’s been mention of baffling above. How much baffle, steel wool, whatever, is needed?

I think the premium catch can makers would tell you the optimum air/oil separator is made of unobtanium, with superconductor cooling towers to eliminate restrictions and maximize oil and contaminant separation. Someone else might tell you (kind of like a member recently quipped), all you need is a beer can stuffed with steel wool, or some such levity.

I went the semi premium route partly because they have a reputation and with YouTube any number of tuners/racers who will call them out if their claims are suspect. I personally think someone with your handiness level could experiment on their own and get to the optimum answer pretty quickly.

In the end, at the rpm levels (at least some of us ) are running at, you are going to catch a bunch of the crud getting pumped out by condensation as it passes through the hose and trickles into the can on the input fitting. Anything you do above that has got to help, maybe until you get to the point where you are restricting airflow. As I understand it, that is the value add of the premium vendors pitch.