Gasketset cilinderhead complete

A cylinder head gasket set restores the seal between the cylinder head, engine block and the connected oil, coolant, intake and exhaust passages. For MAN and Mercedes trucks, buses and vans, the set must always be identified exactly based on the chassis number. Visual comparison or selection by model name alone is never sufficient: engine generation, emission standard, cylinder diameter, cylinder head version, gasket thickness, number of valves and coolant passages may differ within a single engine family. This applies to MAN D08, D15, D20, D26, D28, D30 and D38, and to Mercedes OM 364, OM 366, OM 402, OM 421, OM 422, OM 441, OM 442, OM 457, OM 460, OM 501, OM 502, OM 503, OM 904, OM 906, OM 926, OM 934, OM 936, OM 470, OM 471 and OM 473.

Depending on the engine variant, a complete gasket set includes a cylinder head gasket, valve cover gasket, intake and exhaust manifold gaskets, injector seals, valve stem seals, O-rings for coolant passages and sealing rings for oil supply and return lines. On common-rail engines such as the MAN D26 and D38 or Mercedes OM 471 and OM 473, the seals around injector holders, EGR connections and line pass-throughs must also match the fitted cylinder head exactly.

The cylinder head gasket must be able to withstand high combustion pressure, temperature fluctuations and fluid separation simultaneously. Multi-layer steel gaskets generally consist of profiled steel layers with elastomer coatings and precisely formed sealing beads around cylinders, oil galleries and coolant passages. A cylinder head gasket with a fire ring has a reinforced metal sealing ring around each combustion chamber. This fire ring concentrates the clamping force around the cylinder bore and prevents hot combustion gases from blowing through between the cylinder head and engine block. This is particularly crucial on heavily loaded turbo diesel engines with high peak pressures.

Oversize cylinder head gaskets are intended for engines where the cylinder head surface and/or engine block surface has been surface-ground following warping, corrosion or fire damage. Material removal changes the distance between the cylinder head and piston crown. A thicker gasket compensates for this reduction and maintains the required piston protrusion, compression ratio and clearance between pistons, valves and cylinder head. Only select an oversize gasket after measuring the machining depth, cylinder liner protrusion and specified gasket grade; a thicker cylinder head gasket must never be used to conceal a warped or cracked cylinder head.

A defective cylinder head gasket often causes coolant loss without a visible external leak, overpressure in the expansion tank, hard coolant hoses, white exhaust smoke, unexplained temperature increase or engine oil contaminated with coolant. Leakage between two cylinders can result in compression loss, irregular idling, misfire codes and loss of power. On Mercedes OM 457, OM 460, OM 501 and OM 502, and on MAN D20, D26 and D28, also look for local blow-by marks at the edge of the cylinder head gasket.

Start diagnosis with a pressure test of the cooling system at the specified test pressure and check the pressure loss over a sufficient stabilisation period. Then perform a CO₂ test or analyse combustion gases in the coolant. Measure compression or, preferably, carry out a cylinder leak-down test; air bubbles in the expansion tank during the leak-down test indicate a connection to the cooling circuit. Also check the flatness of the cylinder head and engine block using a calibrated straightedge and feeler gauge, and measure cylinder liner protrusion with a dial indicator.

Only remove the cylinder head after the cause of overheating has been resolved: check the thermostat, water pump, coolant radiator, EGR cooler, cooling circuit and any injector issues. Clean the mating surfaces without creating grooves, remove fluid from bolt holes and use new cylinder head bolts and strictly follow the specified tightening torques, angle turns and tightening sequence. Fit the correct gasket dry and in the specified orientation. Technical support with identification based on the chassis number reduces the risk of selecting the wrong gasket and unnecessary downtime.