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YOUR RESEARCHSurface Marks?
Leading reported evidence
Check so far, i am sure they are
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Performed · outcome unconfirmed · Original poster
These marks are on the four cylinders I have checked so far, I am sure they are on all 6.
Leading evidence: 'Check so far, i am sure they are' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'shape of the chunk' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check cylinder bores i see these marks' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suspected cause
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.
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Suggestion · Original poster
I am in the middle of my intermix repair and while checking my cylinder bores I see these marks.
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shape of the chunk
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Suspected cause
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.
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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?
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.
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.
Jake,
Great advice! Since these marks are on all 6 cylinders though, is it possible that the problem is instead on a common part like the fuel pressure regulator or fuel pump?
I sent Hartech an eMail about these marks and here is their response. I post it here so that others can benefit from the explanation.
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"These marks can be puzzling and we have never been able to absolutely determine what they are or the cause.
The manufacturing process is for a liner to be constructed from a composite mixture of a resin and silicon particles forming a rough shaped porous tube.
These are then located inside a metal casting mould and the molten aluminium is forced in under high pressure that permeates the liner filling up some of the gaps between the particles while burning off some of the resin leaving a porous silicon rich surface with an outer aluminium casing.
Our tests show that the resulting Lokasil part (the bore par which is roughly half the thickness of the visible liner area) is more porous but also stiffer (more brittle and less flexible) than the aluminium.
The wall thickness of the cylinder composite tube combined with the open deck design allows the cylinder to flex under the load of the piston thrust face (that eventually can make the cylinder distort oval enough as a result of �creep� to remain oval by up to 0.25mm after which it usually cracks or �D� chunks).
The cylinder head gasket has circular cut out sections on the top and bottom layer of the triple steel gasket to allow the plastic sealing coating to remain in contact with the cylinder head while this flexing is taking place.
Putting all these facts together - we think these marks are probably minute surface cracks with no measurable depth in the make up of the Lokasil. They are effectively just surface marks that seem to have no mechanical or operational consequences.
There is a variation in the distribution of the aluminium and the amount of silicon and the proportion of resin and the penetration of the aluminium during casting that can very rarely result in some areas actually washing away the surface by up to a half a milimetre � so there is clearly a possibility that these marks are just where a trace of different bonding occurred such that as the cylinder expands and contracts during warming up and cooling and also distorts under load � one specific area is slightly less strong than others and the silicon particles just there � while perfectly well bonded to the substrate internally � never the less at the surface release their bonding strength to the circumferentially adjacent particles.
In any case we have never experienced them becoming a problem and so I think you should ignore it."
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