Tore Down the Honda Engine

[Gangly]

As some of you know, I recently replaced my Honda Pilot engine with a Ridgeline engine because the Pilot engine had a distinct, cyclical, knocking sound. As an update, its been a few weeks since the engine swap and the Pilot is running as good as ever with the Ridgeline engine.

I got curious about the old engine, so I decided to tear it down to see what was going on with it. Overall the engine was pretty clean for 155k miles which made obeservations pretty easy. Although there was a bit of excessive cam journal wear, and some peculiar rod bearing and crank journal bearing patterns, the main culprit appears to be piston slap in cylinder one.

 

[xjfish]

It is always nice to find and visually confirm the cause of an engine noise. I often don't get the chance to do so. I suspect a cylinder balance test may have helped pinpoint before teardown? I bought a Grand Cherokee years ago as a repairable that had a "knock" that was hard to pinpoint. (I initially though it may have been timing chain related noise) The 4.7L had a hole and piston that looked very similar to yours...

 

[Sturgeon]

Pretty good, so what are you going to do?

 

[xjfish]

Pretty good, so what are you going to do?

I suspect he will not be fixing it? His Pilot is fixed. Correct engine repair would be bore and oversize pistons + ? = $$$

 

[tarmy]

Sooo…was that cylinder in the rear bank?

Wifey had one with the v6 where the fuel economy solution shut down the entire rear bank. Many people had problems with the engines eating themselves due to oil pressure issues. Just wondering if that played a roll.

 

[xjfish]

Sooo…was that cylinder in the rear bank?

Yes, cylinder 1 is.

 

[Gangly]

That was cylinder 1. No known oiling issues other than my son driving it with with very little oil in it for a prolonged period. If you look closely at the oil ring, you can see where the oil baked into the corrugations of the ring.

*Edited - Insufficient knowledge to account for my original thought.

 

[Gangly]

Pretty good, so what are you going to do?

I've removed all of the sensors, coil packs, injectors, etc. and will hold onto them in case I might need to replace one at some point on the newer engine.

I'll save a good portion of the bolts since they are quality bolts, just to have as extras.

The block and heads will find their way to a dumpster, but I'll prolly hold onto the cams, crank, and pistons and try to make a lamp or something out of them.

 

[finn]

That was cylinder 1. No known oiling issues other than my son driving it with with very little oil in it for a prolonged period. If you look closely at the oil ring, you can see where the oil baked into the corrugations of the ring, resulting in insufficient oiling between the cylinder walls and piston skirt.

The oil on the skirt is splash from the rotating assembly, or in some cases a piston cooling jet aimed to shoot oil under the piston to cool the crown.

If the oil ring had carbon buildup to the point the expander had unitized, that ring is passing oil and not scraping oil off the wall.

Skirt/wall scoring is caused by inadequate film , ie bore polishing so there is no oil retention in the hone pattern , or excessive heat in the skirt causing the piston to expand beyond design limits, or debris taking up the clearance.

My bet is a failed ring pack, leading to carbon buildup induced bore polishing.

 

[Gangly]

The oil on the skirt is splash from the rotating assembly, or in some cases a piston cooling jet aimed to shoot oil under the piston to cool the crown.

If the oil ring had carbon buildup to the point the expander had unitized, that ring is passing oil and not scraping oil off the wall.

Skirt/wall scoring is caused by inadequate film , ie bore polishing so there is no oil retention in the hone pattern , or excessive heat in the skirt causing the piston to expand beyond design limits, or debris taking up the clearance.

My bet is a failed ring pack, leading to carbon buildup induced bore polishing.

For all I know you may be correct Thanks for the input, I edited my post accordingly.

Heads up though, the oil ring does account for lubrication of the skirt, rings, and cylinder walls and insufficient oil flow through the oil ring will create skirt and cylinder bore damage.

 

[Gangly]

What I'm actually most curious about is the horizontal wear markings on the cam journal. I've never seen that before, it almost resembles cylindrical bearing wear like you might see on a wheel hub, but there are no bearings between the cam journal and head assembly to make that unique pattern.

 

[finn]

For all I know you may be correct Thanks for the input, I edited my post accordingly.

Heads up though, the oil ring does account for lubrication of the skirt, rings, and cylinder walls and insufficient oil flow through the oil ring will create skirt and cylinder bore damage.

34 years engine engineering development experience, including power cylinder development says that’s not exactly correct.

The drilled holes behind the oil ring are drainback holes to keep the oil ring from being flooded and floating on the cylinder walls.

Skirts are splash lube from oil flinging off the bearing side clearance and general windage.

 

[Wrench97]

Lack of oil from when the son ran it for a long time low on oil gets my vote for the damage.

 

[PoorUB]

34 years engine engineering development experience, including power cylinder development says that’s not exactly correct.

The drilled holes behind the oil ring are drainback holes to keep the oil ring from being flooded and floating on the cylinder walls.

Skirts are splash lube from oil flinging off the bearing side clearance and general windage.

Stuck or other wise screwed up oil rings shouldn't cause cylinder scoring. The rings remove oil, not add it.

 

[BurtEggley]

was a master engine and head machinist once upon a time. To me, that looks like a cylinder got hot and scuffed, then over time that material got into the oil and damaged some cam journals. Did you ever have a time when the coolant was low, or it was driven at a really high speed for a long distance? Sometimes the conditions an engine is driven it, say out in the desert on a 100 degree day, at 85 - 90 mph, the heat becomes quite uneven in an engine, and one cylinder or another may overheat, while the overall engine temperature shows normal. Typically the cylinders farthest from the cooling source.

The area between the top arrows shows that oil has been washing over it, cleaning the deposits off. That aligns with the deep scratches, which appear to have begun with scuffing - unless you find something in the block in line with that which may have been shedding debris. The bottom arrow points to the are where the majority of the oil was flowing past the rings, inline also with the scratches. Directly below the head of the bottom arrow is a channel that has been eroded away. Below that are two dark lines. The widest may be a gouge. I would hate to think that happened at the factory when being assembled, but it could have been. Has the engine ever been apart before, for warranty work?

As the piston wore away, you got slapping. Too thin of lubrication can cause scuffing too, like oil that has lost its ability to lubricate either thru being an inferior oil, or used too many miles, etc.. But if it only happened on one, and there is nothing shedding particles near there, it is likely to be a cylinder that got a little hotter - farther from the radiator on a hot day. It is not likely to be detonation damage or the crown would show it.

 

[four.cycle]

block and heads will find their way to a dumpster

scrap metal guys will fight over that block and heads. put it on CL free and let 'em pick it up!~

Lack of oil from when the son ran it for a long time low on oil gets my vote for the damage.

exactomundo.
+ more than likely the conditions described by @BurtEggley as well as @finn ... your location says you're near Houston so I think it's reasonable to assume "hot outside" - the perfect conditions for this kind of disaster when combined with low oil/dirty oil.

 

[roc_on_the_rocks]

Lack of oil from when the son ran it for a long time low on oil gets my vote for the damage.

In my experience rod bearings fail sooner than pistons when lubrication lacks or it's limited.

 

[BurtEggley]

re the scuffing. The shop was in SoCal in the Riverside - San Bernardino area. We used to get a lot of high end car engines coming back from Vegas where one or two cylinders that got the least cooling would scuff. (Or an injector might be working only partially and cause that cylinder to run lean.) In either case the oil would be at the average engine temp. Scuffed pistons, or warped heads where steam collected in the highest spot (where some idiot manufacturers put their temperature sensors for some reason who knows). The owners would say the temp gauge was moving up and up, and then it went back down (as the steam collected) so they thought they were Ok. That engine can be bored over and rebuilt but I seriously doubt that the expense will ever pencil out. It isn't a one of a kind collector car.

 

[four.cycle]

That engine can be bored over and rebuilt but I seriously doubt that the expense will ever pencil out. It isn't a one of a kind collector car.

Not unless you're able to buy all the parts directly from China and have your own machine shop capable of re-boring and installing new sleeves.


Looks like you can pick up a complete used 3.5L in the neighborhood of $1400-$1800 - no way are you going to completely go through that engine for that money.

 

[Gangly]

was a master engine and head machinist once upon a time. To me, that looks like a cylinder got hot and scuffed, then over time that material got into the oil and damaged some cam journals. Did you ever have a time when the coolant was low, or it was driven at a really high speed for a long distance? Sometimes the conditions an engine is driven it, say out in the desert on a 100 degree day, at 85 - 90 mph, the heat becomes quite uneven in an engine, and one cylinder or another may overheat, while the overall engine temperature shows normal. Typically the cylinders farthest from the cooling source.

The area between the top arrows shows that oil has been washing over it, cleaning the deposits off. That aligns with the deep scratches, which appear to have begun with scuffing - unless you find something in the block in line with that which may have been shedding debris. The bottom arrow points to the are where the majority of the oil was flowing past the rings, inline also with the scratches. Directly below the head of the bottom arrow is a channel that has been eroded away. Below that are two dark lines. The widest may be a gouge. I would hate to think that happened at the factory when being assembled, but it could have been. Has the engine ever been apart before, for warranty work?

As the piston wore away, you got slapping. Too thin of lubrication can cause scuffing too, like oil that has lost its ability to lubricate either thru being an inferior oil, or used too many miles, etc.. But if it only happened on one, and there is nothing shedding particles near there, it is likely to be a cylinder that got a little hotter - farther from the radiator on a hot day. It is not likely to be detonation damage or the crown would show it.

That area between the arrows is what I wiped off with a rag, its edges matching the skirt wear is coincidental. I was wiping the top lip of the piston to see if any marring occurred to the top of the piston. Its not oil washing over the surface and cleaning it.

All of the pistons showed skirt wear, this being the most severe. The oil change intervals were shorter than required and the engine oil was Mobile 1 FS. The rest of the engine block is clean with no buildup or sludge present. As I mentioned previously, or maybe in another post, the engine was maintained before my son ran it for a prolonged period of time with extremely low oil levels.

The vehicle has never had cooling issues and it didn't occur in the summertime.

I don't believe the ring pack to be causative at all, nor cooling of the engine to be an issue at all. I believe the other pistons would have exhibited the same degree of damage pretty soon had the engine continued to be driven without the necessary volume of oil, this cylinder and piston just happened to show it first.

I honestly do appreciate your analysis though, your insights are noted and valued.

 

[Gangly]

In my experience rod bearings fail sooner than pistons when lubrication lacks or it's limited.

Rod bearings did have wear, but minor compared to that observed on the skirt.