OM906 Gaskets and Gasket Sets

Plastic or aluminium rocker cover?

What decides the OM906 upper gasket set is the rocker cover material. The plastic-cover and aluminium-cover versions differ in gasket profile and sealing elements, and are tracked under separate part numbers. Ordering without seeing the engine is a frequent source of error. The material can be identified by eye without removing the cover: one photo before ordering is enough.

Does it fit? The OM904 mix-up risk

The OM904 and OM906 are from the same engine family; they differ in cylinder count and share some items. Many parts are listed together as "904/906" in catalogues, meaning that item fits both. But not everything is shared — cylinder head gaskets and set contents in particular diverge. When you see "904/906", whether the part genuinely covers both should be verified.

Upper set and full set

The upper set brings together the gaskets needed whenever the cover comes off: cylinder head gasket, rocker cover gasket, intake and exhaust manifold gaskets and the related seals and O-rings. The full set goes down to the sump and lower group. Because the OM906 upper set comes in two contents depending on cover material, cover information is always requested with a set order.

Cylinder head gasket and thickness grade

On the OM906 too, what decides the head gasket is whether the head face has been machined before. On a skimmed head a standard thickness will not give correct clamping. If the engine history is unknown, the grade should not be chosen without measuring; the wrong thickness leads to oil and water mixing.

Manifold and turbo side

Intake and exhaust manifold gaskets are also available as separate items on the OM906. Material matters most on the exhaust side: a gasket in the wrong material for the operating temperature will leak again within a short time. Turbo connection gaskets and manifold tab geometry can vary with specification, so vehicle type is requested.

When ordering for an OM906

With three items ready the right set goes out first time: (1) rocker cover material — plastic or aluminium, (2) vehicle type — Atego, Axor or bus, (3) whether the engine has been overhauled before. If you have the chassis number, we can derive all three. A photo of the cover settles the material question in one step.

Gaskets by engine

Frequently asked questions about OM906 gaskets

Will a plastic-cover set fit an aluminium cover?

No, it will not. The OM906 upper set is not one fixed parts list: which version you need depends on the rocker cover material, because a plastic-cover engine and an aluminium-cover engine call for a different gasket profile and different sealing elements, sold under separate part numbers. Fitting a set made for a plastic cover onto an aluminium-cover engine means the gasket will not seat correctly against the cover face and is likely to start seeping again before long. Mix-ups usually happen when an order is placed from the engine code alone, without the engine in front of you, because the same OM906 code has been built with both cover materials. Removing the cover is not required to avoid this: the material can be told apart by eye from the outside, so a clear photo of the cover before ordering is normally enough to settle which set is correct on the first try.

Can an OM904 gasket be fitted to an OM906?

Some items are shared and listed together as "904/906" in catalogues. However, cylinder head gaskets and set contents diverge. Whether an item is genuinely shared should be verified per part.

Which vehicles use the OM906?

It is common in the Mercedes-Benz Atego and lighter Axor applications, and in buses, notably the Setra. The same engine can run different specifications in different vehicle types.

How do I identify the cover material?

The rocker cover can be identified by eye; it does not need to come off. If you are unsure, send a photo of the cover and we will confirm.