Cylinder Block Assembly: Testing and Inspection
AH01.00-P-0300-01VA General information on inspecting cylinder walls
General note
If a complaint is made about an engine, for example because of noises, overheating, oil consumption etc., perform a visual inspection of the mounted cylinder head by inspecting with light probe with an endoscope. The following notes should be helpful in assessing the cylinder barrels to allow a professional decision to be made about the condition and further use of the crankcase. If this can cannot be assessed with sufficient security through inspecting with an endoscope then the work "Check compression pressure" and "Check cylinder leakage" must be performed before removal of the cylinder head. AH01.00-N-1300-02A Determine Loss of Pressure at Cylinder
The results of checking should be documented on a repair order. For deviations from the prescribed wear and tolerance values one should particularly determine the direction of the leakage while checking the leaktightness of the cylinder (in the direction valve or in the direction of the crankcase).
In the case of deviating compression pressure values, in particular when not achieving the installation tolerance/new values (measured with a compression recorder), one should check for indications of a fluid lock (e.g. wet piston crown, wet air filter, water-oil-glycol residues).
Individual score marks up fields of score marks:
Ideal condition
A matt gray user interface, no honing pattern, a dry cylinder barrel, without polished sections or mirror polished flats.
It is also possible that irregularities can occur which should be individually assessed.
Ideal condition:
Individual score marks up fields of score marks
Caused by residual waste or soiling during company, e.g. through back pulsation of particle from the catalytic converter or the exhaust system.
Continue to use crankcase.
Ring shaped imprints:
Ring shaped imprints
Visible in the upper and lower reversal range of piston rings, are not a reason for complaint.
Continue to use crankcase.
Brown coloring of cylinder upper surface:
Brown coloring of cylinder upper surface.
Brown coloration (oil varnish) over large areas of the cylinder barrel indicates that the engine has been driven at a high temperature level. This is normal and not a cause for complaint.
Continue to use crankcase.
Pressure gloss marks, smooth spots:
Pressure gloss marks, smooth spots
Individual blank points, e.g. in middle of cylinder or in area of cylinder head bolts. An all-round impression at the piston ring reversing point above and below.
Continue to use crankcase.
Optical stripes, friction marks:
Optical stripes, friction marks
Starting from the first, second or third piston ring, run out after approx. 30 mm. Traces of dry friction marks which cannot be felt, caused by soot particles and oil film being washed off by fuel, e.g. from frequent cold starts associated with short-distance driving. These traces of friction marks which occur principally in area of cylinder head bolts and on pressure side are not a problem provided they are smoothed.
Continue to use crankcase.
Imprint on valve cooling bore for an 8 and 12 cylinder engine:
Imprint on valve cooling bore for an 8 and 12 cylinder engine
The cooling bore in the crankcase shows a different coloration to the cylinder barrel.
Continue to use crankcase.
Corrugated wear of the cylinder barrel:
Corrugated wear of the cylinder barrel
A washboard type surface structure of the cylinder barrel, partially or all around.
Do not use the crankcase anymore.
Roughened mottling, friction scoring:
Roughened mottling, friction scoring
Starting from first, second or third piston ring, tapering to an end only in bottom part of cylinder. Friction marks as described under "Optical streaks, friction marks", in an advanced for becoming friction eroded areas.
If friction eroded areas are perceptible the cylinder barrel is unusable.
Do not use the crankcase anymore.
Piston seizure, eroded areas on the ring:
Piston seizure, eroded areas on the ring
Most of cylinder wall perceptibly roughened over the entire length. Material deposits and perceptible scoring marks on cylinder wall and at piston skirt.
Cylinder barrel unusable.
Do not use the crankcase anymore.