2015 Sierra 5.3 Engine Replacement

Slickracer34 · February 6, 2021

Hey everyone. Sorry if this has been covered before but for some reason I can't do a search in the forums. I have a 2015 Sierra 5.3 with 132K kms. I have had a Range disabler and Magnaflow cat-back pretty much all along, and about 10K kms ago I installed an HPS intake. A couple weeks ago when climbing a hill on the highway at about 3.5K rpms the truck stopped pulling but continued revving and the exhaust changed to a high pitched sound. I backed off and it seemed to catch it's breath but it didn't run right the rest of the week. On that Friday about a mile from my house I stepped on it again and up around 3.5K it did it again and this time it caused damage. #7 cylinder has only 30psi compression and the shop says the cylinder walls are scored and the piston is damaged. They didn't mention any damage to the head. I have not seen the pictures yet and they haven't told me yet what they think happened other than there was oil and coolant on the piston. I'm sure the coolant was spillage from pulling the head. The only code showing was P0307. There was no audible tapping or knocking sound but the exhaust sounds hollow and garbled when idling and had a really bad sour smell when driving up on the flat bed. Maybe a ring land failure from detonation? If it was detonation could the aftermarket intake have possibly anything to do with it? TIA for any opinions.

Edited February 6, 2021 by Slickracer34

CamGTP · February 6, 2021

The intake won't have anything to do with what may have happened.

Sounds like bad luck and something let go. I would only be guessing at the cause from where I sit as well. Could be a ring failure that scored the wall, injector issue that lead to it or who knows what else.

Slickracer34 · February 6, 2021

1 hour ago, CamGTP said:

The intake won't have anything to do with what may have happened.

Sounds like bad luck and something let go. I would only be guessing at the cause from where I sit as well. Could be a ring failure that scored the wall, injector issue that lead to it or who knows what else.

Yeah I didn't think so either. If the intake was the issue I should have got a code for lean condition or something. It never threw a code until it was in my driveway puking 10 mins after it let go. On a side note the oil pump grenaded at 15K kms and they didn't replace the motor. It got flushed and they said it was fine and everybody I knew said they should have replaced it. I said if that oil pump failure did any damage it'll show before my warranty is up. My warranty is up at 140K so I'm glad that whatever it was that happened it happened now.

PPK · February 9, 2021

It could have been detonation... and then a broken ring.If you catch it immediately - pull the piston and replace it - you can just have some marks in the cylinder. With a broken ring.. any period of time running it- that ring - the broken part that is a half circle sized or so - the ends will gouge the cyl wall.

When you pull the piston and see the ring - and the top ring - you can speculate detonation caused ring land / broken ring failure was the result....

i know this the hard way....

Edited February 9, 2021 by PPK

Slickracer34 · February 11, 2021

On 2/8/2021 at 7:22 PM, PPK said:

It could have been detonation... and then a broken ring.If you catch it immediately - pull the piston and replace it - you can just have some marks in the cylinder. With a broken ring.. any period of time running it- that ring - the broken part that is a half circle sized or so - the ends will gouge the cyl wall.

When you pull the piston and see the ring - and the top ring - you can speculate detonation caused ring land / broken ring failure was the result....

i know this the hard way....

I just got my truck back today with the new motor. All the work order said is there was moisture in the exhaust manifold and past the valves. There was blow by and a hair line crack in the cylinder. I never did get to see the photos they took of the damage. I'm pretty sure whatever it was that happened wasn't caused by my cold air intake. There must be a thousand or more people running intakes on these motors with no issues whatsoever. The dealer said this is the first L83 they have ever seen this happen to. Was your detonation issue on your L83?

PPK · February 12, 2021

Detonation.. yes.. A Ford. broken ring lands - and rings. i think the piston broke first - and then the rings of course without support went. Detonation in a pre-90s Ford without the sensors and controls of fuel injected engines...

Slickracer34 · May 8, 2021

Here's an update on my engine replacement. I'll never know what happened to the original motor since it's been shipped back. The dealer somehow lost all the photos of the damage and seem to dance around all my questions when I push them on it. Oh well at least I have a new motor and 2K kms of warranty left. The more I run it through my mind and remember what it sounded like when it happened I am positive it was detonation that killed it. I've only ever run 87 octane and two weeks ago I switched to 91. Since then my mileage has gone from 17-18L/100km to 13.5-15L/100km. I think that's about 14mpg to 17mpg but not sure. It runs better, idles smoother, and feels more responsive. I plan on putting the HPS intake back on when I put my summer wheels on and will be running 91 octane from now on. Just my two cents.