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Video Engine Management

Video Cylinder Head 1
Video Cylinder Head 2
Video Cylinder Head 3
Video Cylinder Head 4
Video Cylinder Head 5
Video Cylinder Head 6
Video Cylinder Head 7
Video Cylinder Head 8
Video Cylinder Head 9
Video Cylinder Head 10
Video Cylinder Head Repair
Video Cylinder Head Gasket

Video Exchange of Gases
Video Comb. Chamber Shape
Video Cam
Video Camshaft
Video Adjustable Camshaft 1
Video Adjustable Camshaft 2
Video Adjustable Camshaft 3
Video Cambelt
Video Cambelt (assembly)
Video Camshaft Timing Chain
Video Camshaft Timing Chain
Video Upright Shaft
Video Timing Diagram
Video Valves
Video Valve drive
Video Natrium Cooled Valve
Video Valve Spring
Video Valve Stem Guide
Video Valve Seat
Video Valve Seat Angle
Video Valve Stem Sealing
Video Valve Overlap
Video Valve Play Adjustment
Video Valve Contr. (desmo.)
Video Hydraulic Lifter
Video Operating Valves
Video Var. Valve Timing 1
Video Var. Valve Timing 2
Video Var. Valve Lift 1
Video Var. Valve Lift 2
Video Drawrod Engine

Video Engine Control 1
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          A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Hydraulic Valve-play Adjustment









Assignment

It automatically compensates and adjusts the valve-play clearance. The amount of effort put into maintaining the engines is reduced, because a regular adjustment of the valves is no longer necessary. Due to the complete valve-play compensation, the valve-opening is optimised and the engine is quieter.

Function

The cylinder head and the valves are made of different materials. Apart from this, the more a valve is in operation, the longer it becomes, this is because the spring at the end of the valve-shaft pulls the valve back and because it is abruptly stopped by the valve-disc at the other end. This is why, in engines without the hydraulic valve-play adjustment, a valve-play of 0,1 to 0,4 mm is necessary, which cools the valve, so that the valve-disc can close securely.

With the hydraulic valve-play adjustment, valve-play is not necessary. In this case, a cylindrical space, from which only a small amount of oil can escape, is filled with oil pressure through a check-valve. This construction provides a valve-play compensation. With the direct drive, the cylinder can be integrated into the cup-tappets, this however, increases in moving mass. This can be avoided if, e.g., the pivot points of the cam followers are hydraulically adjusted (see figure). The valve springs and the cam surfaces are then less subject to strain.

There are sometimes problems with the hydraulic valve-play adjustment. Brief rattling after starting the engine is mostly not that serious. Should the rattling persist, then either the check valve or the variable filling space is clogged or the oil lead is leaky. In this case, there's nothing that can be adjusted and a so-called engine purge seldom brings the desired success. At least it's (only) the tappet cover(s) and possibly the camshaft(s) which have to be removed or dismantled to replace the respective parts.

By the way, on the strength of an unfavourable compression test, established mechanics have, after taking the cylinder head apart, been known to have found no real defect. It would have been better if they had first had a look at the hydraulic lifters, sparing the customer the cost of needless work. 04/09




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Translator: Don Leslie - Email: lesdon@t-online.de

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