Concurred on all 3


Clean the top of the piston before you proceed further with anything else

 

you said you found liquid in the cylinder when you did the borescope.....what kind of fluid was it? oil, fuel, coolant?

 

I'm not sure. Oil coolant and fuel? Here's a video.

 

My only retort, and I'm no expert by any means, is that you seem to have eliminated everything else. About the only things you can't "see" are the rings. I agree, a ring failure should probably score the cylinder, but, maybe there's a failure mode where that doesn't happen.

In your video, the first look at the liquid seemed to show it as non-viscous, like water. Didn't look thick enough to be oil. And, it didn't really look like anti-freeze to me either.

- Jack

 

I don't know what the liquid is because my theory - that's all it is - is that the fuel not being burnt could thin the oil? However, the color sure looks like oil and coolant to me. I just don't know.

 

Did you try a wet compression test before you tore it down? Or check the compression on the cylinders on either side of the dead one? Is the head flat? Too late to do a pressure check with it apart.

 

judging by the pictures and the video, to me it looks like coolant.

I'd get the head milled since you already have it off and somehow clean up the coolant passages, they are pretty gunked up to me.

 

I wish I had done such tests, but no, I didn't.

The coolant that came out looked great. Actually considering this engine has almost 200k, everything looks pretty good. I'll do a flush anyway.

 

If the intake valve isn't opening it won't have much compression. It was just a wild guess since no other simple explanation was forthcoming.

 

Now that's an interesting thought! Makes sense to me too. You'd exhaust the existing volume during the exhaust stroke, pull vacuum during intake and have nothing to compress during the compression stroke. You'd basically be back at one atmosphere (zero compression) at the top of the stroke.

- Jack

 

which picture is the cyl w/ the problem?

 

In the video looks like you have a head gasket problem. should have test for compression in the cooling system before the rip down. Also hit the tops of all the valve/springs w/ small hammer to see if they all sound the same. (Broken spring) The 1st picture look like a gasket leak on the head by the water port.

 

Were all the spark plugs out of the head when you did the compression test or did ya leave some in? Just thinking that compression may be leaking between 2 cyl's next door to each other??. take the next door plug out and compression goes away????

 

But, wouldn't that cause two cylinders to have poor compression?

- Jack

 

Jack very true! But I have seen what I have I said happen by not checking things in order! Guys have missed the 2nd cyl not having compression. Could be a crack piston, head,bad cam, bad rings or head gasket for sure. Its hard to fix human error.