Why do DOD/AFM Lifters Fail?
Why do DOD/AFM Lifters Fail? I have a 2013 Silverado, 143,000 miles and it developed a very loud valvetrain "tick" all of a sudden on the road.
Knew it was DOD or rocker related, so after taking the passenger valve cover off I found the #4 intake pushrod was loose, and ~.5" lower than the rest. Rockers, and rocker stand all in good shape.The valley cover seals looked good.
So-why do they fail? Engine oil changed very regularly, very clean internals. Truck never beat on.
I'm thinking of just changing out the 8 DOD lifters and hoping it's good for another 100k. What GM part number should I use? I hear GM updated the lifters to a more reliable lifter.
Thanks
Knew it was DOD or rocker related, so after taking the passenger valve cover off I found the #4 intake pushrod was loose, and ~.5" lower than the rest. Rockers, and rocker stand all in good shape.The valley cover seals looked good.
So-why do they fail? Engine oil changed very regularly, very clean internals. Truck never beat on.
I'm thinking of just changing out the 8 DOD lifters and hoping it's good for another 100k. What GM part number should I use? I hear GM updated the lifters to a more reliable lifter.
Thanks
TECH Senior Member
Joined: Jun 2016
Posts: 22,290
Likes: 3,615
From: Central Cal.
Simply put, it's a more complicated lifter than the "regular" ones. And the more complicated or complex something is, the higher the likelihood is for failure. Maybe a form of Murphy's Law?
I've dealt with two different trucks failing, both were oil pressure to the AFM lifters. First one is my truck with a partially blocked filter screen and possibly a leaky VLOM. Second one was a friend's truck that ran low on oil due to crazy oil consumption issues (another awesome AFM side-effect). Both instances seem that oil pressure was lowered in the AFM system.
I think your best case is to replace all the AFM lifters and the VLOM and make sure the filter screen under the oil pressure sender is clean. Then check your oil often to make sure you're not consuming a lot. Or just disable AFM in the computer and deal with slightly lower fuel economy.
I think your best case is to replace all the AFM lifters and the VLOM and make sure the filter screen under the oil pressure sender is clean. Then check your oil often to make sure you're not consuming a lot. Or just disable AFM in the computer and deal with slightly lower fuel economy.
TECH Senior Member
Joined: Jun 2016
Posts: 22,290
Likes: 3,615
From: Central Cal.
I doubt you'll notice any real fuel mileage difference. My wife's Suburban has DOD and the only times I've seen it in 4cyl. mode is while coasting and RARELY at steady cruise. Being a heavy truck like this with a 5.3L, it does not surprise me being in 8cyl. mode about 95% of the time. I'd rather it didn't have DOD because of the extra complexity.
I've dealt with two different trucks failing, both were oil pressure to the AFM lifters. First one is my truck with a partially blocked filter screen and possibly a leaky VLOM. Second one was a friend's truck that ran low on oil due to crazy oil consumption issues (another awesome AFM side-effect). Both instances seem that oil pressure was lowered in the AFM system.
I think your best case is to replace all the AFM lifters and the VLOM and make sure the filter screen under the oil pressure sender is clean. Then check your oil often to make sure you're not consuming a lot. Or just disable AFM in the computer and deal with slightly lower fuel economy.
I think your best case is to replace all the AFM lifters and the VLOM and make sure the filter screen under the oil pressure sender is clean. Then check your oil often to make sure you're not consuming a lot. Or just disable AFM in the computer and deal with slightly lower fuel economy.
I doubt you'll notice any real fuel mileage difference. My wife's Suburban has DOD and the only times I've seen it in 4cyl. mode is while coasting and RARELY at steady cruise. Being a heavy truck like this with a 5.3L, it does not surprise me being in 8cyl. mode about 95% of the time. I'd rather it didn't have DOD because of the extra complexity.
At least it's not a terrible job to do, as long as they don't fail far from home.
So far the most frustrating part is getting the exhaust manifolds away from the head to remove that row of bolts... manifold to exhaust flange is damn tight
VALVE LIFTERS - GM (12645725) should be the part number i need, correct?
VALVE LIFTERS - GM (12645725) should be the part number i need, correct?
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I was thinking................... if this happens again, what's stoping me from tuning out DOD/AFM in the PCM and running a longer pushrod on the lifter that failed?? I would think the failed lifter would stay pretty static as far as pushrod cup height. I could measure how long of a pushrod I would need and that cylinder should operate as normal then, correct?
I was thinking................... if this happens again, what's stoping me from tuning out DOD/AFM in the PCM and running a longer pushrod on the lifter that failed?? I would think the failed lifter would stay pretty static as far as pushrod cup height. I could measure how long of a pushrod I would need and that cylinder should operate as normal then, correct?