The Main Failure of The Valve Train

The valve train failure mainly has the gas distribution phase misalignment and valve train noise. Gas distribution phase misalignment is mainly synchronous belt installation position is incorrect or synchronous belt tooth wear caused by slippage, in the event of this failure should immediately replace the synchronous belt, and according to the relevant content of the engine disassembly re-installation synchronous belt. Troubleshooting and troubleshooting of the gas valve train parts are described below.

Camshaft rattle

Phenomenon is in the upper part of the engine rhythmic more dull heavy "clatter" sound. It is obvious at medium speed, and the sound is chaotic or disappears at high speed.

The reason is that the axial clearance of the camshaft is too large and axial runout is produced. The camshaft has bending and twisting deformation. The cam working surface is worn. The camshaft journal is worn and the radial clearance is too large.

Diagnosis and troubleshooting: Check the axial clearance of the camshaft. If its axial clearance is too large, the thrust plate should be replaced; if it is serious, the camshaft should be replaced.

If the axial clearance of the camshaft is normal, it indicates that there are bad phenomena such as camshaft bending and deformation, wear of this wheel or wear of camshaft journals. In this case, you should decompose the air distribution mechanism, find out the specific cause and replace the camshaft as appropriate.

Valve foot rattling

The phenomenon is the engine idle, the cylinder head cover rhythmic "tada tada" sound. Engine speed increases, the sound increases. Engine temperature changes or for the fire test, the sound remains the same.

The reasons are improper adjustment of valve clearance, valve rod end and valve clearance adjusting screw wear, valve clearance adjusting screw lock nut loose and cam wear or rocker arm arc working surface wear.

Diagnosis and troubleshooting: remove the cylinder head cover, check whether the lock nut of the valve clearance adjusting screw is loose; check the valve clearance value, and readjust as appropriate. Check the valve rod end face and adjusting screw wear, if necessary, replace the valve or adjusting screw. Check the wear of the cam and rocker arm circular arc working surface, and replace the camshaft or rocker arm as appropriate.

Valve springs rattle

Phenomenon is the engine idle speed there is a clear "chugging" sound. Each speed has a crisp sound, multiple valve springs are bad, the body has shaking phenomenon.

The reason is that the valve springs are too soft or broken.

Diagnosis and exclusion: remove the cylinder head cover, pry the valve springs with a spinning tool, if the spring is broken can be clearly seen. Broken springs should be replaced.

Still pry the valve spring with a spinning tool, idle engine, if the sound disappears, that is, the spring is too soft. Springs such as too soft, must be replaced.

Valve seat rattle

The phenomenon is rhythmically similar to valve foot rattling, but much louder than the sound of valve foot rattling. When the engine speed is certain, the sound is sometimes large and sometimes small, and accompanied by crushing sound. When the engine is running at low speed, the sound is crisp, the sound increases at high speed and becomes chaotic.

The reason has valve seat ring and cylinder head valve seat ring seat hole with insufficient interference, valve seat ring set into the cylinder head valve seat ring seat hole, rolling edge when the seat ring is not pressed firmly. As well as the valve seat ring powder metallurgy quality is poor, heat deformation to loosen.

Diagnosis and exclusion: remove the cylinder head cover, after inspection is not valve foot ring and valve spring ring, can be concluded that the valve seat ring ring. Decomposition of the valve train after further inspection, if necessary, reaming the valve seat ring seat hole, replace the loose valve seat ring, and ensure that it is pressed into a sufficient amount of interference.