AFM Failure Prevention?

Tech discussions on the L77 6.0L V8.
dtully
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AFM Failure Prevention?

Post by dtully »

So like I said in my intro post I’m looking at a 9c1 that had a new motor dropped in at 82k, it’s sitting at 137k now, so 55k on the new motor. I’m going to guess that an afm failure grenaded the first motor. Having this happen again before I get the cash together for a full deletion is my biggest hang-up on pulling the trigger on buying this thing. Is there any way to maximize the life of the afm system or prevent a failure? The PD that had it before did it’s oil changes every 5k like clockwork and clearly that didn’t help lol
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Re: AFM Failure Prevention?

Post by smwalker »

Well I doubt you will idle it as long as they did in everyday use. That could be one factor. But other consumers have had the same issue with other GM models that have the same set up. SO think t is just a crap shoot really. Enjoy it till you can't, then deal with it.
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Mooseman
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Re: AFM Failure Prevention?

Post by Mooseman »

You can prevent AFM failure by disabling it, either by disconnecting the vacuum sensor on the brake booster (cheap and easy but will give a CEL and code), a tune (preferred and has other benefits) or an AFM disabling device plugged into the OBD port (more expensive but more convenient).

AFM usually fails when the lifter fails to operate normally again when going from V4 to V8 mode and stays collapsed. By stopping it from going into V4 mode, you will prevent this from happening because it won't go into that collapsed mode.

However, there have been instances of complete failures when the lifter and cam failed and ground into each other sending shrapnel through the whole engine. This usually happened on engines that had high idling hours or just bad luck.
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dtully
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Re: AFM Failure Prevention?

Post by dtully »

Has anyone sorted out why the lifters get stuck in the first place? The only thing that I’ve found, and I don’t even know if it’s correct, is the secondary oil filter before the VLOM gets dirty and crap gets into the lifters making them stick? If that is correct, maybe cleaning/changing that filter and using high quality oil will do the trick?
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Re: AFM Failure Prevention?

Post by Mooseman »

I have read that there were two things with the first years. One was a bad lifter design in the collapsing mechanism that made them prone to get stuck. Second was the VLOM that was redesigned for better oil flow. That filter, when clogged, would throw a low oil pressure code even though the oiling system was fine. Neither really fixed it.

Lots of info here: http://www.lt1swap.com/afm_delete.htm" onclick="window.open(this.href);return false;
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CrashTestDummy
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Re: AFM Failure Prevention?

Post by CrashTestDummy »

dtully wrote:Has anyone sorted out why the lifters get stuck in the first place? The only thing that I’ve found, and I don’t even know if it’s correct, is the secondary oil filter before the VLOM gets dirty and crap gets into the lifters making them stick? If that is correct, maybe cleaning/changing that filter and using high quality oil will do the trick?
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Re: AFM Failure Prevention?

Post by Mooseman »

Valve Lifter Oil Manifold (aka: lifter valley cover)
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Re: AFM Failure Prevention?

Post by CrashTestDummy »

Mooseman wrote:Valve Lifter Oil Manifold (aka: lifter valley cover)
Thank you, Mooseman!!

Most of the failures I've read about usually indicate a roller failed, which also usually takes a cam lobe out. That's what happened with our '12 when it was in service, at least according to the job writeup by the dealer.

Since most departments will be running their vehicles under warranty, they'll at least be using a proper-spec oil in order to maintain that important warranty. They'll either already be using a high-quality oil, if not Mobil-1 Dexos, or be having the local GM dealer do their oil changes, so one would hope they are.
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Re: AFM Failure Prevention?

Post by HoldenPPV »

How many idle hours is considered a high amount?
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Re: AFM Failure Prevention?

Post by Mooseman »

From what I have read, 1 hour of engine idling is equivalent to 100 km, which seems to jive with this:
https://itstillruns.com/convert-hours-e ... 78869.html" onclick="window.open(this.href);return false;

I have seen some at my work (CVPI though) that had over 9000 hours, which would come to 900 000km (560 000 miles) and still running. This may be in addition to actual mileage so that might bring the total to over 1M Km.
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