2015 3.6L Pentastar Cylinder Borescope Result

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I was wondering if the resident experts could weigh in on the results of borescoping the cylinders on my 2015 Jeep Wrangler with 122,000 miles. All of the piston crowns have a fair amount of carbon buildup, but also have these yellow and white specs that I can't identify. Cylinder No. 1 appears to have a fairly deep gouge in the top of the piston, and Cylinder No. 3 valves have some odd looking pitting on the face around the edges. The cylinder walls all have a good crosshatch, but there are some locations of irregular scratching and what could be slight pitting.

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Interesting pics indeed. It's hard to determine based on what I see on my monitor.

What symptoms lead to scoping it?
 
A yellowish glaze on a spark plug is signs that the cylinder was running too hot / lean but only some of the time - like under hard acceleration. Would that apply here??
 
The unusual scratches on the cylinder wall is probably from when the tool was withdrawn from the cylinder. A non issue.
The pit looking marks on the cylinder walls might be casting flaws, or a small rust pit, also likely a non issue.
The carbon is coming off the piston and exposing aluminum below, which is discolored a bit, looking yellow.
The pit on the piston is likely an index mark. Remember, when something is ingested, it bounces around creating a wonderful pattern of destruction. Not just one "ding".
Can't tell on those valves. That might simply be carbon buildup that's creating various patterns.

Borescopes provide notoriously misleading images. They often use an LED light which is NOT a high CRI source. (color rendition index) In the aviation world, inexpensive borescopes lead to massive problems, due to misinterpretations. I use a "mini-maglight" grain of wheat bulb soldered onto two small single strand copper wires (like old telephone wire) and attached to a battery pack with 2 AA batteries and a small switch. It provides a much better light source and a very clear understanding of what you are looking at.

I do find it odd that the carbon pattern is so uneven. Are you ingesting water?

mcb4.bmp
 
The divot you are seeing is on all the pistons, it's the locating mark so they are installed the right way. Here's an example on a new piston:
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The gouge/indentation I showed in the 2nd picture only exists on the piston in cylinder 1. I looked thoroughly, and there is nothing like that on the other pistons. The shape is not triangular like you show, it looks more like an irregular lima bean.
 
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Interesting pics indeed. It's hard to determine based on what I see on my monitor.

What symptoms lead to scoping it?

I have it apart to replace the oil cooler housing due to failure, and wanted to assess engine health to determine if it would be a good idea to try to unload it now or keep it for another 10 years. Main symptom is that on 87 octane fuel that the manual recommends, it will ping upon hard acceleration from 1500-2500 RPM so I have to run 89 octane or higher. It developed the typical rocker tick from the left bank at 80,000 miles, and the LH cylinder head, all rockers and lifters, and one cam were replaced by dealer when it was still under warranty. I replaced the thermostat which failed open at around 110,000 miles. I also had done a relative compression test with a lab scope last year, and thought there was too much spread between the peaks. I am planning on doing a traditional compression and leakdown test on it today.

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Any history on this engine?
fuel used? oil brands/type? intervals? fuel system cleaners?

History is that I purchased the vehicle brand new, and have owned it since mile 5. I have only used E10 Top Tier fuel including Chevron, Costco and Arco. Oil has been 5W20 Pennzoil Platinum with a 5,000 mile change interval. Fuel system cleaner was seafoam in the gas tank for the first several years, and then Chevron Techron with a 5,000 mile interval.
 
A yellowish glaze on a spark plug is signs that the cylinder was running too hot / lean but only some of the time - like under hard acceleration. Would that apply here??

This is a picture of one of the original plugs that I replaced at 80,000 miles. I'll post a picture later on of one of the plugs I just took out.

Spark_Plug.jpg
 
The unusual scratches on the cylinder wall is probably from when the tool was withdrawn from the cylinder. A non issue.
The pit looking marks on the cylinder walls might be casting flaws, or a small rust pit, also likely a non issue.
The carbon is coming off the piston and exposing aluminum below, which is discolored a bit, looking yellow.
The pit on the piston is likely an index mark. Remember, when something is ingested, it bounces around creating a wonderful pattern of destruction. Not just one "ding".
Can't tell on those valves. That might simply be carbon buildup that's creating various patterns.

Borescopes provide notoriously misleading images. They often use an LED light which is NOT a high CRI source. (color rendition index) In the aviation world, inexpensive borescopes lead to massive problems, due to misinterpretations. I use a "mini-maglight" grain of wheat bulb soldered onto two small single strand copper wires (like old telephone wire) and attached to a battery pack with 2 AA batteries and a small switch. It provides a much better light source and a very clear understanding of what you are looking at.

I do find it odd that the carbon pattern is so uneven. Are you ingesting water?

mcb4.bmp

I typically use high volume top tier fuel stations and the vehicle is driven constantly, so I don't think there would be water in the fuel. How else would water get into the system? The carbon buildup looks similar on all the pistons, but only piston No. 1 has that indentation/gouge.
 
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those pistons look just like the ones in my friend's 2013 3.6 Chrysler minivan at about 200,000 miles.
i saw them while doing plugs and an oil cooler
 
those pistons look just like the ones in my friend's 2013 3.6 Chrysler minivan at about 200,000 miles.
i saw them while doing plugs and an oil cooler

Did you notice any "pitting" looking marks on the valve faces, or the gouge/indentation only on cylinder 1 piston?
 
Did you notice any "pitting" looking marks on the valve faces, or the gouge/indentation only on cylinder 1 piston?
i wasn't able to see the valves, just the piston. the indent in the piston looks like a casting mark, or possibly a bubble in the casting. i don't remember seeing any indents in my friend's piston, but I wasn't looking super close. if the piston made it this far I wouldn't worry about it.
 
Here are a few more pictures of the gouge/indentation in piston No. 1. Could this be erosion occurring due to detonation, or damage due to debris going through the engine?

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PHO00017.JPG
 
The gouge/indentation I showed in the 2nd picture only exists on the piston in cylinder 1. I looked thoroughly, and there is nothing like that on the other pistons. The shape is not triangular like you show, it looks more like an irregular lima bean.
I just gave you an example, the one in your pic looks like a crescent, which is common. I expect the others may be concealed by carbon so you didn't see them. It is, in my opinion, far too uniform a mark to be anything other than a directional marker.
 
Honestly, nothing there looks terrible to me. Unless you have an actual complaint of performance or use, I would not be loosing sleep over this.

Run a few bottles of Techron if you want a warm fuzzy you did something.
 
I just gave you an example, the one in your pic looks like a crescent, which is common. I expect the others may be concealed by carbon so you didn't see them. It is, in my opinion, far too uniform a mark to be anything other than a directional marker.

The part number of the Mopar Piston/Rod Assy is 5184347AH. I pulled the stock image of the piston off the Mopar.com Estore, and the one of the used piston from Ebay. It looks like there is supposed to be a circular divot in the piston crown based on these images, so do you think thats what we are looking at on mine? Perhaps it looks crescent shaped because the other half of the circle has a chunk of carbon built up?


Piston_Mopar.jpg
Piston.jpg
 
Honestly, nothing there looks terrible to me. Unless you have an actual complaint of performance or use, I would not be loosing sleep over this.

Run a few bottles of Techron if you want a warm fuzzy you did something.

The complaint of performance is that it will ping on the manual recommended 87 octane fuel and I have to run 89 or 92 to eliminate it. You don't have any concerns about the pitting looking marks in the valves?
 
First picture is Cylinder No. 5 spark plug and second picture is Cylinder No. 1 spark plug I just removed at 122,000 miles and they have been in since 80,000 miles. Note the oil on the threads on the Cylinder 5 plug, which also exists on the Cylinder 6 plug. I do notice some oil on the back of the throttle plate and in the intake usually when I am servicing it, but I never thought much about it because I replaced the PCV valve at 80,000 miles. I usually fill oil to the upper mark on the dipstick which is just shy of 6 quarts, so not sure if it could be blowing oil into the intake due to being overfilled.

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