Engine all (4xWD, CAR, Light transporter, smart)
Improved engine outputs, as well as fully-automated production processes for the sealing of major assemblies in the drivetrain have significantly changed the requirements profile for sealants. Seals are divided up into two different systems. There are the dynamic systems in which one of the surfaces to be sealed is in motion (for example, cylinder/piston seals or shaft/housing seals). Static sealing systems are designed to not permit any relative motion. A typical example is the seal between two bolted housing halves (the oil pan to the crankcase, for example). In the field of static sealing systems, the advantages of liquid seals are increasingly being used.
Liquid seals no longer perform the sealing work in the classic sense, but serve merely to equalize the sealing surfaces. This is why a clean working method in accordance with the instructions is absolutely essential.
The sealing surfaces must be thoroughly cleaned before the sealant is applied. For cleaning, use only clean tools and clean, lint-free rags. Remove any residue of cleaning agents and loosened contaminants. Use only the sealant listed in the repair specifications. Apply sealant at specified areas only and process within a period of 10 minutes. Do not spread the sealant bead.
The incorrect or excessive application of sealant can result in considerable damage to the major assembly, or even its total failure. Overflowing sealing material in the engine can block the various oil holes and ducts in the main oil circuit and in the cylinder head.
Consequential faults are possible, such as malfunctions of the camshaft adjustment and inadequate lubrication of the crankshaft and camshaft bearing points. Clogged oil holes to the vacuum pump result in malfunctions in the wastegate actuation of the turbocharger and adverse effects at the coolant pump.
The sealant specifications with regard to the thickness of the sealant application must be complied with. The following examples clearly shows how the sealant application expands when the component parts are joined.
Sealant application 1.5 mm and 3.0 mm.
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Sealant application in pressed condition (under glass pane). Sealant distribution at 10 mm and 17 mm width.
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Below are some examples in which the sealant specifications have not been complied with:
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