Mercedes-Benz S400 Engine Front Cover Replacement Cost

Engine front (timing) covers are seldom replaced, however, the gaskets for these covers are replaced at some point for many vehicles. Some will last the lifetime of the vehicle, some will be ignored if the leak is small or only seepage, but many will leak and need repair. The average timing cover reseal occurs between 80,000 and 160,000 miles, and it is safe to say that time and use both play a role in the development of oil leaks.

If the timing cover gasket is leaking, or the timing cover is broken, cracked, or warped, the technician will notice right away, and recommend reseal or replacement. Timing belt engines often have warped plastic components, and these will cause a rubbing noise that the technician can hear. After a visual inspection, the technician will understand the issue clearly and recommend repair. In the case of timing component replacement, the technician will inspect the inner side of the timing cover to ensure that timing chain slap has not worn grooves into the cover. If the cover is extremely worn from contact with timing components, likely the chain, it will be replaced to prevent future fracturing. Slight wear from contact will likely be ignored.

In order to access the timing cover, many components must be removed. This includes all belt driven accessories mounted on the front of the engine, many cooling system components, possibly air conditioning system components other than the air conditioning compressor, and likely the valve covers and the oil pan. Once all of these components, and likely others, are removed, the timing cover mounting fasteners can be removed, possibly in sequence. Once fasteners are removed, the timing cover will be gently pried from the engine block, cylinder heads, and oil pan to break the silicone seal. Sealing surfaces on the engine and front cover will be thoroughly cleaned, any additional work items will be performed, and silicone sealant will be applied to all sealing surfaces on the front cover. The front cover will be replaced onto the clean, dry engine block, and the fasteners will be installed, tightened lightly, and torqued to specification in sequence.

When the front cover is removed the technician will have access to inspect all timing components. Since replacement of any timing components require the timing cover be removed, if any signs of abnormal wear are present, no matter how severe, those timing components should be replaced. Also, common points of failure have been identified on many models of vehicles, these typically include timing chain guide rails, timing chain tensioners, and timing chain guide rail pins. These should be replaced on models where failure is common, and the parts used should come directly from the manufacturer to ensure the latest revision is installed.

When removing and installing the front cover, even a new front cover, it is imperative that the front cover be installed in the exact sequence and at the exact torque specifications recommended by the manufacturer. This will prevent warpage to the front cover, and possible stress fractures. The front seal for the engine crankshaft is also installed in the front cover, and this should be replaced any time the front cover is removed. Lastly, the oil pan should be flushed when the front cover is removed, as this will prevent particulate matter from servicing the front cover from clogging or partially clogging the oil pump strainer.

This is not a job for the DIY technician unless they happen to be very skilled and knowledgeable with engine repair and timing component operation and installation. If timing components are found to be worn, the vehicle will likely require a professional technician to service the vehicle. Again, except for the most qualified DIY mechanics, this should not be attempted at home.