Car (2007 C2S) suddenly started making the noises in the audio. This was recorded when the engine was fully warmed up, the blips are to 1300-1400 rpm.

It's in the shop right now and the mechanic can't pin point it yet. Any pointers would be appreciated.

- It's not doing it while cold. It's intermittent and happens only once it heats up, past 165-170F coolant temperature.
- It's doing it with the accessory belt removed so it's not the accessories.
- It seems to be tracking the rpm roughly, not exactly and it's almost never doing it on idle.
- Mechanic had the stethoscope on it from the bottom of the engine, on the front, rear and the cylinder heads and it doesn't seem to be coming from anywhere there.
- Car runs fine, full power, no codes, doesn't burn oil, exhaust tips are clean, last oil analysis was 300 miles ago and was stellar.

What could it be? Evap solenoid?

Thanks.

 

Making noises in the audio? Not sure what you mean by that. Noises from the "audio" (speakers?) is a sign of some electrical problem, a grounding issue, cross talk.

The noise appeared suddenly. Was the car worked on any before the noise appeared?

Is the oil level, coolant level, power steerging fluid level ok?

Have you considered dropping the oil filter housing and dumping the oil and filter into a *clean* drain pan and looking for debris? My thinking is this could be (could be) a case of some serious internal engine problem and if it is to the point it is making noise then debris in the oil filter and oil filter housing oil might be a sign. I don't think you'll find anything scary but maybe you want to check just in case.

The clip is not very long and the racing the engine doesn't help but somethings come to mind.

The mechanic has practically eliminated the noise from inside the engine but it is not from the accessory drive system.

(A long shot but someone reported a noise present and not from the engine and present with the belt removed. Long story short it proved to be some bolt in the crank shaft pulley. Not one of the bolts that holds the pulley to the crank but just a loose bolt that somehow got inside the cavity of the pulley and was rattling around in there. Also, some few weeks ago when I restarted my Boxster engine after just a few minutes it was making a noise that I was sure was a bad accessory drive (water pump) or possibly a bad idler bearing, tensioner bearing or even a bad belt. Had the car falt bedded to the dealer and after the car was dropped off at the dealer and the engine started the noise was gone. The tech checked the car over very thoroughly and found nothing wrong. I drove the car just like the day before and was unable to produce the noise. The tech/SM thinks something got caught in the accessory drive and this was the source of the noise. On the back of the truck on the 30 mile ride to the dealer whatever it was got blown out. If not a bolt in the crankshaft pulley maybe a small rock or pebble or some other debris?)

Be sure you check, the mechanic checks, for a loose plug or a loose exhaust heat shield. Give a listen to the converters.

(My Boxster had a loose converter brick that buzzed something fierce when hot and when cold knocked in such a way I thought the crankshaft was suffering from too much end play.)

 

Oil change was done literally 50 km ago and then again, once it started rattling, just in case (paranoia). Nothing in the oil. Like I said, oil analysis was stellar too.

This is intermittent too. My mechanic reported it stopped doing it Friday afternoon which didn't make his job easier.

Thanks for the suggestions, I'll suggest it to the mechanic. It could be the exhaust.