Vaz -21213 Repair Manual page 10

Typical knocking or thumping noticeable at sudden throttle opening at idle which intensifies with higher crankshaft rate. Excessive endfloat
of crankshaft causes sharper irregular knocking, especially noticeable during smooth increase or decrease in crankshaft speed.
1. Early ignition
2. Insufficient pressure oil
3. Loose flywheel securing bolts
4. Excessive main bearing running clearance
5. Excessive thrust washers-to-crankshaft clearance
Big-end bearing knocking is sharper than that of main bearings. It is noticeable during engine idle at sudden throttle opening. The origin of
knocking can be easily identified through switching off spark plugs one at a time.
1. Insufficient oil pressure
2. Excessive big-end bearing running clearance
Thumping noise caused by piston «runout» in cylinder. Most noticeable at low crankshaft speed and under load.
1. Excessive piston-to-cylinder bore clearance
2. Excessive gudgeon pin-to-piston groove clearance
Excessive valve clearances cause typical regular noise; its frequency is lower than the frequency of any other engine noise, since the valves
are operated by camshaft rotating at half the crankshaft speed.
1. Excessive valve clearances
2. Broken valve spring
3. Excessive valve-to-guide clearance
4. Worn camshaft lobes
5. Loose locknut of adjuster bolt
Noise from camshaft operation line is caused by clearances between engagement elements and becomes noticeable in general engine noise
at low crankshaft speed.
1. Loose chain caused by general wear
2. Broken chain tensioner shoe or damper
3. Seized chain tensioner plunger rod
1. Foreign particles entrapped under oil pump relief valve
2. Seized oil pressure relief valve
3. Worn oil pump gears
4. Excessive main bearing running clearance
5. Excessive camshaft bearing journal-to-bearing housing clearance
6. Incorrect oil grade or inappropriate oil quality
1. Seized oil pressure relief valve
2. Excessively tough spring of oil pressure relief valve
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Main bearing knocking
1. Adjust ignition timing
2. Refer to subsection «Insufficient oil pressure at idle»
3. Tighten bolts to torque specified
4. Grind journals and renew bearing shells
5. Fit new thrust washers, check clearance
Big-end bearing knocking
1. Refer to «Insufficient oil pressure at idle»
2. Fit new bearing shells and regrind journals
Piston slap
1. Renew pistons, rebore and hone cylinders
2. Fit new rings or new pistons with rings
Knocking of intake or exhaust valves
1. Adjust clearances
2. Renew spring
3. Replace worn parts
4. Renew camshaft and levers
5. Adjust clearance between lever and cam, tighten locknut
Excessive noise of camshaft operation line
1. Tighten chain
2. Renew tensioner shoe or damper
3. Eliminate seizure
Insufficient oil pressure at warm engine idle
1. Clean valve from foreign particles and flash, clean oil pump
2. Renew valve
3. Repair oil pump
4. Turn journals and renew bearing shells
5. Renew camshaft or bearing housing
6. Change oil as recommended in Attachment 4
Excessive oil pressure on warm engine
1. Renew valve
2. Renew spring