General Information On Checking Camshafts And Bearing Points Of Camshafts - AH05.20-P-1000-09SZ
Engine all (4xWD, CAR, Light transporter, smart)
The following figures and notes aid in assessing the camshaft and its bearing points. They should provide for a professional decision-making aid regarding condition and continued use. The illustrated damage profiles that follow are only a selection of possible forms of damage. Not all possible damage profiles can be shown here. When assessing forms of damage, always incorporate the surface condition of the camshaft and bearing points into the damage diagnosis.
Wear or damage to the camshaft or camshaft bearing point is often caused by:
- Lack of engine oil
- Poor engine oil quality (oil viscosity) or thinning of the engine oil, e.g. through fuel entry
- Delayed maintenance
- Soiled or damaged oil filter
- Fault in oil circuit; e.g. oil pressure is too low
- Poor cleaning during engine repair
- Excess sealant after an engine repair
- Failure to observe tightening sequence
After an engine repair, fill oil circuit with approved engine oil before starting. Then crank engine several times with starter until oil pressure is established.
Cylinder head camshaft bearing and valve cover without damage in as new condition.
Continue using cylinder head and camshafts:
Camshafts with normal running tracks.
Camshaft bearing with normal running tracks.
Camshaft bearing in valve cover with normal running tracks.
Camshafts with traces of processing and hold-down tool. Processing traces and running tracks on the camshafts between the bearing points do not result in any function impairment.
Score marks in the camshaft and in the roller-type rocker arm caused by dirt particles that have been pulled through.
Micro pitting on the cams or the camshaft as a result of unfavorable lubrication conditions. Micro pitting can be caused by aging or worn engine oil, poor engine oil viscosity, high engine oil temperature or low lubricating film thickness.
Do not continue using camshaft and roller-type rocker arm:
Significant pitting on the camshaft. The cam is partially to completely worn and partially chipped. The same picture also shows the corresponding roller on the roller-type rocker arm.
Significant pitting on roller-type rocker arm. The roller on the roller-type rocker arm is partially to completely worn and partially chipped. The same picture also shows the corresponding cam.
Do not continue using cylinder head and camshafts:
Camshafts and camshaft bearing points seized.
Camshafts seized on engine 157, 276, 278 due to failure to observe tightening of the high-pressure pump (HDP).