noisy idle noise - "diesel" like sound

[Lacostas]

Hello again to this great community!

I decided to write here for an issue im having lately. My 2.7 (2003) boxster engine is doing a "knocking" sound on idle.

About the noise:
- Almost Irrelevant if warm-cold engine.
- It Reminds me of a diesel engine car sound ( )
- No CEL or anything related, spark plugs/coils/oil new

Only thing im a bit guilty is that the sound started happening when i switched to 95 Octane, but maybe its irrelevant ?

No idea of the Serpentine belt condition by the way.

Thanks to All!

[alm001]

My water pump sounded like you describe when the bearing started to go. Pull your belt off and check the WP.

[Gilles]

My CS developed a lifter noise while idling and a friend of mine (Porsche specialized shop) suggested to try Liqui Moly "hydraulic lifter additive" which I used on the next oil change (LM 5-W40) and it helped a lot to reduce the lifter noise, you may want to try it.

[Bruich10]

I had the “diesel” noise late autumn/early spring - extremely annoying sound. Proved to be the servopump and the generator making noises at idle. I did not do the replacements myself but according to my independent technician it was not a straightforward job.
Mine is 2003 S with 190.000 km on the clock - now spinning like a cat again.

[Beelzy]

Sounds like the water pump. Mine made the same noise right before it started
dumping coolant.

[ndfrigi]

Have u tried opening the engine access behind the seats? try to use a plastic tube and use it to hear each part of the engine where the noise/sound is coming from.
Water pump, idler pulleys, alternator, power steering and AC motor.

[Bruich10]

My waterpump went down 5 years ago at about 125.000 km - sound maybe similar but much more aggressive - and if the sound came “lately” it does not correspond with my wp experience.
Mine was: Sound - leak - wp bonkers!
But of course it is worth checking everything,