General information on inspecting cylinder walls - AH01.00-P-0300-01A
ENGINE 122, 134, 135, 200, 270, 271.951, 274, 276.9, 607, 611, 612, 613, 622, 626, 628, 629, 639, 642, 646, 647, 648, 651
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 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 cannot be assessed with sufficient certainty through inspection using an endoscope, then the "Check compression pressure" and "Check cylinder leakage" operations must be performed before removal of the cylinder head.
The results of the check must be documented on a repair order. In case of deviations from the prescribed wear and tolerance values, the cylinder leakage check must focus on determining the direction of leakage (towards valve or towards crankcase).
In case of deviating compression pressure values, in particular if the measurements taken with a compression recorder are below the installation tolerance and/or new values, a check must be made for signs of a fluid lock (e.g. wet piston crowns, wet air filter, water-oil-glycol residues).
A magnet can be used to perform a quick check on which type of cylinder barrel is involved, because cast-iron cylinder barrels are magnetic.
Engine with cast-iron cylinder barrels
Glazing, smooth spots
Individual blank points, e.g. in the middle of the cylinder barrel or around the cylinder head bolts.
Reuse crankcase.
Visible stripes, friction marks
Starting from reverse area of the upper piston ring tapering downwards.
Traces of friction marks which cannot be felt, caused by oil film being washed off by fuel, for example from many cold starts when driving short distances.
Friction marks occurring mainly around the cylinder head bolts and on the pressure side are not a problem provided that they are smoothed out.
The piston rings are not damaged.
Reuse crankcase.
Ring shaped imprints
Visible imprints on cylinder barrel in the upper and lower reverse area of piston rings are not a cause for complaint.
Reuse crankcase.
Rotary bright, reflective, polished cylinder barrel
Starting from the reverse area of the upper piston ring with measurable, partial cylinder wear.
The cylinder barrel is unusable.
Do not reuse the crankcase.
Rough streaks, friction scoring
Starting from first and second piston ring, tapering to an end only in bottom part of cylinder. Progressive signs of friction lead to friction score marks.
Where these signs of friction are perceptible, the cylinder barrel is unusable.
The piston rings may be damaged.
Do not reuse the crankcase.
Continuous individual traces of scratch
Caused by soiling, for example, by the back-pulsation of soot particles from the exhaust system.
Reuse crankcase.
Piston seizure
Most of cylinder wall perceptibly roughened over the entire length.
Material deposits and perceptible scoring marks on cylinder wall and at piston skirt.
The cylinder barrel is unusable.
Do not reuse the crankcase.
Brown coloration of cylinder barrel
A brown coloration over large areas of the cylinder barrel is oil varnish and indicates that the engine has been driven at a high temperature level.
Oil varnish above piston ring zone is normal and is not a reason for complaint.
Reuse crankcase provided no impermissible cylinder distortion is present.