After a 30 minute drive home yesterday, I had just made it back into my neighborhood, cruising along at 25-30 mph. Out of nowhere, heard a squealing sound, which I thought at first was something on the radio. Turned the radio down, and it was still there. Not as high pitched as I'd consider a belt squeal to be - much more moderate than that. And constant, not rhythmic. I immediately clutched in and let revs fall to idle, no change. Came to a stop, no change. Gave a gentle rev of the engine, and it did not seem to track rpm. I quickly shut the motor off and restarted it - the noise was gone. Did not come back in the 1/3 mile to my house.
I'm about to take the car out again for a few errands, and I'll pay close attention to see if it happens again. Any ideas on a noise like this that doesn't seem speed or rpm dependent?
FWIW, I replaced spark plugs and accessory belt about 6 months back while chasing a chirping/squeal sound (loose plugs was the culprit). Also had a new clutch/flywheel/pp put on the car last month. I have ~56k miles on the odometer. Original water pump.
-Jeff
I'm gonna go with a failing water pump. Mine went at 40K and from everything I read, that's about normal. If yours is at 56K you are well past due a failure.
Possible vacuum leak? Check your AOS too (puff of smoke when you start up).
Anything else I can think of would be RPM related (belt, water pump, pulleys, etc.).
If it didn't change pitch with engine speed, it's unlike to be a bearing or anything connected to the serpentine belt. AOS squeal will change with engine speed, too (it will decrease as RPM increases)- when this happened on my 986S, it was NOT subtle. Was it just the engine bay cooling fan, perhaps? It'll come on sometimes at lot speeds on hot days.
Okay, back from running errands. Probably 20 miles total with a few stops sprinkled in. Car ran absolutely perfect, not a hint of anything out of the ordinary. I certainly feel better than before I left. But it's still a puzzle...
No smoke at startup. If I had a vacuum leak, wouldn't I expect to see a "visit workshop" message on the dash?
Well, it WAS hot yesterday, I was driving home from the beach. Somewhat aggressively, with several bursts to 90"ish" on the highway. If the engine and turbo were both hot, slowing down in my neighborhood could possibly trigger extra cooling. I'm used to hearing the radiator fans up front, but not behind me. And this was not a normal level of fan noise, whatever it was. Much louder. Which would suggest whatever fan it was may have an issue.
I think we're all on the same page thinking that since it's not coupled to rpm, it's not a belt driven accessory. Fan is an interesting thought...especially if it's one that runs rarely. I suppose there is also a pump associated with the turbo's intercooler plumbing to the front radiator, since that's a closed system. Or maybe even something with the AC system? I'll make sure to turn off the AC if I hear the sound again.
It's also entirely possible that I'm the world's biggest idiot.
I was trying to think back to what I had in the trunk, in case anything I was carrying could have made some noise. Well, I did leave my cell phone back there. Inside a stack of aluminum foil pans (unused extras from the beachside BBQ I was at). Hmmm... what if the phone had a calendar alert or a stack of emails/message, and vibrated for several seconds...
So, I just went into the kitchen and grabbed the phone, the stack of foil pans, an aim-a-flame lighter, sunscreen, etc. (everything that had been thrown in there while packing up) and started playing around with the arrangement...while calling my phone from another line. Well, believe it or not, I was able to get the aluminum pan to sing in a tone pretty similar to what I heard yesterday.
Not certain I'm convinced the phone would buzz long enough for what I heard yesterday, but who knows... ?
glad it doesn't seem to be anything wrong - be careful the combination of things doesn't start a fire or signalling outer space
Love it! Science!!!
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