I "warned" my friend who bought a 2013 5.3 about the AFM and he asked one of the mechanics at the dealer to explain the system to him. In short the mechanic told him he should be fine, and usually what they see to be the cause of AFM issues is poor maintenance, specifically dirty oil or waiting to long to service oil (is basically the info my friend relayed back to me). So that goes in line with your thinking.

If people are trusting the oil life monitors and going 10k-15k on an oil change, that may be part of it as well. Some synthetics are rated for that now but It seems like most on here don't trust those long oil change intervals.

 

Holy wall of text.

But most just shut off AFM and put a catch can and be done with it. The catch can (a good one) will catch most of the oil that otherwise would have been put back into the intake.

Just drain it regularly, and most importantly, do regular, responsible oil changes (not the 10k plus the truck will let you go sometimes) and you'll likely be just fine.

 

So why not block the fresh air tube entirely and just allow blow-by into your catch can/manifold?

 

:lol: lot of it.

One point is that the engine suffers from this as well with the flow of moisture and air. I feel like a can is only part of it. Although if the can steps down fitting side essentially it's doing the same thing. I'm actually surprised to get a response though. Agree or disagree just out there to think about.

 

So why not block the fresh air tube entirely and just allow blow-by into your catch can/manifold?

That would be with the addition of a PCV valve. If not you would have full vacuum on the engine.

 

 

:lol: lot of it.

One point is that the engine suffers from this as well with the flow of moisture and air. I feel like a can is only part of it. Although if the can steps down fitting side essentially it's doing the same thing. I'm actually surprised to get a response though. Agree or disagree just out there to think about.

You're saying too much fresh air is going into the crankcase and causing more problems. Have you experimented with reducing the amount and seen any notable change or is this a WAG?

I'm interested because my '16 4.3 is sitting with 4K miles and I'd like to do what I can to prevent these AFM/DI problems.

 

Soooo basically what you are saying is that we should change our oil more frequently? But the TV and mini-Kevin Harvick say we can go a whole year if we use their oil :lol: :lol: :lol: And TV would never lie to us

 

dRewville: Why would a grown man go to that much trouble to show his a$$ and ignorance?
.... He wouldn't! Now is as good of a time as any. Time to grow up man... One day you can Have real conversations, maybe even your own but you have to start somewhere.

 

calm down buddy, its gonna be ok

 

You're saying too much fresh air is going into the crankcase and causing more problems. Have you experimented with reducing the amount and seen any notable change or is this a WAG?

I'm interested because my '16 4.3 is sitting with 4K miles and I'd like to do what I can to prevent these AFM/DI problems.

Whatever you or anyone does to or for their vehicles is your choice. I'm not selling anything. I'm simply offering some info that may help. Thats what the purpose of the forum is for. But I'm not getting kickbacks from oil companies or whomever. Lol The first post seems pretty self explanatory. If I can help I will , I don't need to convince anyone. Neither should they be convinced. If anyone is interested consider this and make your own logical decision. But Imo if the first first post isn't convincing enough then, I'm not sure you'll ever be convinced. Basically it's about the basics fundamental facts not just my vehicle. But yes I have done this to my Sierra. Yes I had an oil consumption issue. Yes I had noisy lifters. Yes, I stopped both for about 40k mi so far. Yes I have the original spark plugs @ 107k. Yes AFM is active.

 

Don't know about all that other stuff but will say I think most people underservice their PCV system. I mean for something that costs like what $10 ? Most people never even change their PCV valve. Even mechanics I know that should know better.
Back in the day if the PCV system failed it would be immediately evident because you would physically see oil in the air cleaner. Now most vehicles have the breather side ported well away from the air cleaner and if the system fails its something you might not notice unless you actually remove the plenum.

 

So, could you do a write up with pictures and specs so that those who wanted to go this route could do so. I emphasis pictures because I agree with one of the other posters, you are a novelist.

 

You're saying too much fresh air is going into the crankcase and causing more problems. Have you experimented with reducing the amount and seen any notable change or is this a WAG?

I'm interested because my '16 4.3 is sitting with 4K miles and I'd like to do what I can to prevent these AFM/DI problems.

Whatever you or anyone does to or for their vehicles is your choice. I'm not selling anything. I'm simply offering some info that may help. Thats what the purpose of the forum is for. But I'm not getting kickbacks from oil companies or whomever. Lol The first post seems pretty self explanatory. If I can help I will , I don't need to convince anyone. Neither should they be convinced. If anyone is interested consider this and make your own logical decision. But Imo if the first first post isn't convincing enough then, I'm not sure you'll ever be convinced. Basically it's about the basics fundamental facts not just my vehicle. But yes I have done this to my Sierra. Yes I had an oil consumption issue. Yes I had noisy lifters. Yes, I stopped both for about 40k mi so far. Yes I have the original spark plugs @ 107k. Yes AFM is active.

No convincing needed here. I'm onboard with keeping the dirty crankcase fumes out of the intake to help with both DI and AFM problems. Never gave a thought that fresh air was a source of contamination to the oil or that too much was coming into the crankcase then into the intake. I admit to not fully understanding what happens with air flow direction and volume under different driving conditions, WOT, coasting downhill, etc.

Have you posted elsewhere what you've done to your Sierra PCV system?
thanks

 

Yes, you have given many a long posts about your theory.

Please make a instructional write up explaining how implement your fix, and the steps you took with your truck. With paragraphs and pictures, rather than a wall of text.

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Ill try to get some pics but the detail IMO is more important than the "wall" of text. It's an explanation with the ideas and theory behind. A picture does not give that detail. Also there is not a lot to this and different ways to go about it as stated. The basic principle is limiting the amount of flow. Which can be done many different ways. If you have a catch can, install a 1/8" NPT reducer from you size if larger.

Mine is cut from the 10mm Nylon tube with 5/16 heat shrunken with 1/4" tube heated into it. From there is goes to a push lock to 1/8" NPT into the outlet side of a small filter, using a 40 micron tin/copper particulate/moisture separator element. From the inlet side it comes back out through the 1/4" tube to the 5/16-10mm to the valve cover in the same setup as the intake side. On the passenger side, I split the line and inserted the 5/16 with 1/4" tube inside it and put the entire thing back together.

 

Pictures (with a detailed description) are worth a thousand words. The average guy reading even that last post will have absolutely no clue what you're talking about without a reference.

But that is a neat setup

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If you're doing what it sounds like you're doing, don't take this personal, but I don't think that's a good idea at all. Restricting air flow of your crankcase breather is likely to force oil into places it ought not to be.

 

Still not 100% sure what your doing (that's where pics come in) but it does sound like you are trying to limit the amount of vapors that can escape the crank case.

I'm my opinion, that's not the best thing to do. To me, that's asking to blow out some seals. No different than taking your axle breather, and restricting that.

The ideal setup would be a simple open breather system. Just vent any vapors straight out. Almost all of the older diesel (heavy duty) had a road draft tube. Just a tube going from the valve cover right out to under the truck. No filters, no nonsense.

The newer motors still have a similar setup depending on the application. For example, I work for International and some of out motors can have an open breather put on them and others can't. School busses for example, can not.

Even the "open" breather still has a filter on it to catch the oil which drains back into the oil pan.

The closed breathers have a real issue of letting oil pass into the intake which really gums up the turbo and charge air coolers.

 

Yeah the outside air isn't the source of contamination. The blow by from combustion is the source of contamination.

 

If you're doing what it sounds like you're doing, don't take this personal, but I don't think that's a good idea at all. Restricting air flow of your crankcase breather is likely to force oil into places it ought not to be.

No problems here. But I have to disagree obviously. I do agree with the contamination of blow by but not that it is the only source. As far as blowing a seal or forcing oil into places I believe my engine would have to be worn out to come close to that but I will add a pressure gauge and check it under load etc. I will be surprised if build any positive pressure, if so I believe it will be minimal.

 

In theory, in a motor that is in sound condition, you will have more "pressure" at idle and lower rpm. And less "pressure" at higher rpm and higher engine load. This is due to the compression making the rings seal better.

This is most easily seen in the diesel side of things. If you get a motor that was sitting idle alot, the cylinder liners can become glazed over and shiny, and you then start to notice compression entering the bottom end.

But a diesel is different than a gas motor since its bad to see a shiny cylinder wall on a diesel. Whereas a gas motor, that's the norm. I just rebuilt a motor at work with 500k on it that still had the original cross hatching on the cylinder walls.

But I digress. It will be interesting to see if your way does anything beneficial over the usually catch can setup.

 

I think OP said he's been running this for 40K and it had an effect on lifter noise and oil useage. At what point does one say he might be onto something?

apcnc, are you using a catch can or only the restrictions in the PCV hoses?

 

Yes I'm using a filter as a can. Tin/copper 40 micron element with a small poly carbonate bowl. 3 oz maybe. I had dropped the size of the of my line to .18 and just recently dropped to .125.

Btw... I did put a gauge one the system with the line running through the window. The needle did not move so I removed the line to see if any positive pressure comes out ... Only vacuum and it's still a considerable amount our vacuum being reduced to 1/4 capacity.

 

Also it's was measured with a tee straight off the line coming out of the valve cover. Went up to 80 mph normal and hard acceleration if anyone is interested in that. Normal vacuum loss for a second on open throttle but no positive pressure enough to measure or feel.