I am in the middle of my intermix repair and while checking my cylinder bores I see these marks. They seem to be non-structural and looks almost like simple blemishes on the casting. In doing some research I have seen hints of it in other pics but no real discussion on what they are. Can anybody help? These marks are on the four cylinders I have checked so far, I am sure they are on all 6.

Thanks

2000 C2 Cab with 176K miles.

 

I'm no expert any means, but this could be "d-chunking." But the reason it gets it name is due to the shape of the chunk that comes off the cylinder wall. Might be worth looking into.

 

I forgot to mention that there is a definite crack on the 4-6 cylinder head which I believe is the source of the intermix. As for the "d-chunk" would not the crack be more pronounced? This looks more like somebody marked the surface with a pen.

 

Almost looks like water or solvent "High Water" lines from washing it while the block was horizontal in the wash tub. Are they on the bottoms of both sides?

 

maybe do a dye check

http://www.magnaflux.com/Products/Li...5/Default.aspx

 

The marks are exactly the same on the four cylinders I have checked.

 

They could arise from where the molten alum. came together as the block was cast.

With 176K miles on the engine if they are from d-chunking it is the slowest development of d-chunking on record.

Besides, d-chunking is a 3.4l engine issue and the chunk comes form the top inch or two of the cylinder.

If you run a finger nail over the blemish and feel no catch or ridge or anything my WAG is it nothing to worry about.

 

Fpb111, I think I will do the dye penetrant like you suggested. But I wonder how cracks would materialize this way (if they turn out to be cracks). Any thoughts?

 

Macster, I did run my fingernail through it and I could not feel anything. I looked at it pretty closely and other than the marks, there are no other tell tale signs it may be cracks. I am hopeful it is nothing to worry about too, but I want to be sure so I will do the dye penetrant like fpb111 suggests.

 

Anything on the water side of the cyllnder you see or feel?

 

Nothing I can tell from the other side either. It is harder to "see" from that perspective though.

 

Marc- Isn't his engine a 3.4? Am I missing something?

 

?? clys starting to go oval, stress in the same places across the all the cyls??

I think that /\ is a Looong shot.

 

There are a number of dye types. Some don't need developer.
This cracked head pic has been floating around for a few years.
Not sure which dye they used on it.

 

It is indeed a 3.4l.