General Information On Checking Valves, Valve Seats And Valve Guides - AH05.30-P-1000-02SZ
Engine All (4xWD, CAR, Light transporter, smart)
The following figures and notes aid in assessing the valves, valve seats and valve guides in the cylinder head. 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 valves, valve seats and valve guides into the damage diagnosis.
Wear or damage to the valves, valve seats and valve guides in the cylinder head are often caused by:
- Poor engine oil quality (oil viscosity) or thinning of the engine oil, e.g. through fuel entry
- Delayed maintenance
- Faulty engine timing
- Poor cleaning during engine repair
- Poor fuel grade
- Faulty assembly
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.
Valve body
Shown on engine 272 with two removed valves and removed spark plug
Continue to use valves:
Valves with normal combustion residue, shown on spark-ignition engine. Combustion residue in the combustion chamber may be caused by the fuel quality, the driving profile and the engine oil used.
Valves with normal combustion residue, shown on spark-ignition engine. Combustion residue in the combustion chamber may be caused by the fuel quality, the driving profile and the engine oil used.
Valves with normal combustion residue, shown on diesel engine. Combustion residue in the combustion chamber may be caused by the fuel quality, the driving profile and the engine oil used.
Valves severely sooted due to carbon deposits.
If complaint occurred due to damage on valve stem or valve guide, replace valve or cylinder head.
Otherwise, the complaint will reoccur after a few kilometers.
Carbon deposits in the combustion chamber can be caused by defective piston rings, defective valve stem seals, damage to the cylinder barrel, incorrect engine oil or incorrect fuel.
Intake valves with carbon deposits on valve disk. Clean intake valves with carbon deposits and continue to use if no damage is visible on valve stem.
Continue to use cylinder head:
Due to compliance with installation tolerances, reworking the valve seat in the cylinder head or valve guides is fundamentally not permitted.
The valve seat in the cylinder head must display a uniform contact pattern all the way round or be uniformly wide all the way round.
Do not continue using valves and cylinder head:
Exhaust valve burnt through at valve disk.
The complaint may occur for reasons such as:
- Insufficient cooling
- Seat ring wear in cylinder head
- Foreign objects in combustion chamber
- Material fault in valve disk
Valve seat worn in cylinder head.
The complaint may occur for reasons such as:
- Valve guide knocked out in cylinder head
- Valve seat ring not pressed into cylinder head correctly
Exhaust valve seat burnt through.
The complaint may occur for reasons such as:
- Valve guide knocked out in cylinder head
- Valve seat ring not pressed into cylinder head correctly
- Foreign objects
Valve guide worn and knocked out.
The complaint may occur for reasons such as:
- Inadequate lubrication in valve guide
- Damaged valve stem
Valve guide loosened or broken.
The complaint may occur for reasons such as:
- Incorrect mounting
- Foreign objects
Do not continue using valves; check area of valve seat rings and valve guides in cylinder head:
Valves positioned on pistons.
The complaint may occur for reasons such as:
- Incorrect engine timing
- Engine timing chain skipped
- Engine overspeed
Valves bent in shaft.