My 2.5L (103,000 mi., running Mobil 1 10-30) was running fine, but after travelling back from Phoenix to SD, I suddenly hear a consistent tapping when engine runs at low RPM's. i thought sure that I just needed oil, but even after adding almost a qt., the tapping, rapping persists. I had my mechanic look at it, but he reports that valve train is not in need of adjustment, cylinder compression is normal, and plugs not burned or wet. It starts fine, idles smooth (though clackety), and is maintaining normal performance/RPM levels. It just sounds like an old sewing machine .
Mechanic fears I may have cracked a piston skirt, but wouldn't that have caused an engine seize?...any ideas at all?

Any observations and thoughts are appreciated! Thanks

 

It could be the power steering pump or alternator or other part not the engine.

Try running it with the belt off and see if it goes away if so its not the engine just don't do it if the engine is already HOT.

ha ha forgot the 2.5 uses an efan to cool it off listen to the efan it could be the problem

 

mechanics stethoscope can usually track down tapping sounds.. run it over your valve cover; and any other frame; assemblies; back of power steering pump and so on.. and you can usually find the tapping..

I had a tapping; my rockers/lifters make a litlte noise.. guess that happens with age..

but there is another tapping from the Tensioner pully you can see it instead of gliding its more of julting.. result of **** poor machinging/design and luberication of the dayco factory in china or where ever they claim its made.. i had put it on the back of the frame of it and located the sound very clear..

Secondly the AC compressor can also make a similar sound as they wear out.. i know mine kinda makes this rattle noise while its on.. i suspect a bearing is going out but not quite to the point of failure yet. dont think its the clutch either.. think its internally.

which caused an extra tapping sound.... Just throwing that out there..

 

i had a 97 2.5 that cracked piston skirts around 150000 miles. just driving one day and it started ticking like it had a bad exhaust leak. dropped the pane and saw the problem right away.