PISTON SLAP
Moderator: RichardW
PISTON SLAP
I KNOW THIS IS A HARD QUESTION TO ANSWER BUT CAN ANYONE DESCRIBE WHAT PISTON SLAP SOUNDS LIKE COMPARED WITH VALVE GEAR NOISE
Yes - hard question - how to describe a particular mechanical sound scheme [:p]
My present '89 BX16 (230Kkm/144Kmiles) has suffered from a previuos owners "extra oil filter" fitment - which apparently was able to "clean" the engine oil. This of course with the result that engine oil was not replaced - only topped up for longish time - and in turn caused unduly wear in engine.
The result is a very distinctive noise from engine at partial load (coasting) - noise not present at idle or acceleration.
The sound is best described as a constant "pokkety - pokkety - pokkety" [:D][:D][:D]
- like a soft knocking sound.
This I've traced to be piston slap - because of the ineffective lubrication - the piston (light-alloy) has worn to ovals against the liners.
It is known however that this type of noise may also come from worn conrod bearing shells (big ends) - but usually this noise scheme is more like a ticking than a knocking sound.
Worn conrod small end bushings may have the same sound - but with a somewhat higher pitch - very close to valve gear noise.
If the noise is a heavy knocking present mostly under load - then it's worn main shaft bearing shells.
If the knocking noise is more like a thumping knock constant under any engine load - it's likely worn main shaft endfloat shells.
It's a bit of a bugger job to exactly trace the origin of a particular noise scheme from any engine. Allways start with simple things like undoing all drivebelts (NOT cambelt [:)]) and do a short test run.
Then removing all plugs - the engine turned back & forth - it's quite easy to test for conrod slap by a feeler on the piston crown.
Valve clearance testing is evident - but camshaft slap test needs the cam run freely without valve spring pressure present - no easy job.
My present '89 BX16 (230Kkm/144Kmiles) has suffered from a previuos owners "extra oil filter" fitment - which apparently was able to "clean" the engine oil. This of course with the result that engine oil was not replaced - only topped up for longish time - and in turn caused unduly wear in engine.
The result is a very distinctive noise from engine at partial load (coasting) - noise not present at idle or acceleration.
The sound is best described as a constant "pokkety - pokkety - pokkety" [:D][:D][:D]
- like a soft knocking sound.
This I've traced to be piston slap - because of the ineffective lubrication - the piston (light-alloy) has worn to ovals against the liners.
It is known however that this type of noise may also come from worn conrod bearing shells (big ends) - but usually this noise scheme is more like a ticking than a knocking sound.
Worn conrod small end bushings may have the same sound - but with a somewhat higher pitch - very close to valve gear noise.
If the noise is a heavy knocking present mostly under load - then it's worn main shaft bearing shells.
If the knocking noise is more like a thumping knock constant under any engine load - it's likely worn main shaft endfloat shells.
It's a bit of a bugger job to exactly trace the origin of a particular noise scheme from any engine. Allways start with simple things like undoing all drivebelts (NOT cambelt [:)]) and do a short test run.
Then removing all plugs - the engine turned back & forth - it's quite easy to test for conrod slap by a feeler on the piston crown.
Valve clearance testing is evident - but camshaft slap test needs the cam run freely without valve spring pressure present - no easy job.
Its just that when I start up my zx 1.4 the engine runs as sweet as a nut. But if you leave it idling for a couple of minutes a loudish tapping noise becomes noticeable. The noise goes when the engine is at running temp. Its sounds like valve gear noise i.e. one of the tappets out of adjustment, I have listened to them with a screw driver against the valve cover and the noise doesnt seem to becoming from there I cant really pinpoint where its coming from. I have noticed that when you put the car on full lock i.e. straining the power steering pump the noise seems to fade but come back when the load is taken off.
The engine also had its engine oil(comma or Valvoline semi synthetic oil) and filter (purflux) replaced every 3000 miles since we purchased the car with 20,000 miles and previous to this a full citroen service history, however the citroen service where done a bit late i.e. 9000 service at 13,000 and 18000 miles at 23000 miles. So really it was only the first one which can be described as the lengthy one.
The engine also had its engine oil(comma or Valvoline semi synthetic oil) and filter (purflux) replaced every 3000 miles since we purchased the car with 20,000 miles and previous to this a full citroen service history, however the citroen service where done a bit late i.e. 9000 service at 13,000 and 18000 miles at 23000 miles. So really it was only the first one which can be described as the lengthy one.
Well -
Why did you keep that as a secret in 1. place [?]
Now it's clear to me your engine has been best taken care of [:I]
Try that simple trick : remove any auxillary drivebelt for a short test run - to reveal any noise from auxillary equipment - like your servopump or generator or whatever is driven by such belts.
Why did you keep that as a secret in 1. place [?]
Now it's clear to me your engine has been best taken care of [:I]
Try that simple trick : remove any auxillary drivebelt for a short test run - to reveal any noise from auxillary equipment - like your servopump or generator or whatever is driven by such belts.