Does this rumbling noise sound like the idler pulleys? - Page 2 - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I have a rumbling noise that occurs at idle most of the time, moreso when the car is cold. I managed to capture the noise in this video . Before I order the 2 idler pulleys, am I on the right track here? Thanks as always in advance!

If you remove the belt, you can turn ALL the pulleys one at a time to see which one needs attention..............

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Ah great! Assume I'm looking to be able to recreate a noise of some description while turning them by hand?

Yes, a rumble or similar sound and feel.

….is very bad news. I have seen three different Boxsters go up in flames after an idler pulley failure. Belt friction set that thing on fire.

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I got access to it today while I'm waiting for time to take the belt off. I can hear the noise much better with the access panel off. Can someone take a look at this latest video that shows the rumble a lot better and let me know if I'm on the right track with the pulleys, or is this loud enough that it could be something else? Regardless I'll be taking the belt off to check the pulley bearings as @JFP in PA mentioned, but wanted to check in case this is something else that I would need parts for so I can get them ordered.

I also think it is one of the bearings of one of the pulleys. Take the opportunity to renew the belt as well. If the AC compressor might be the culprit, switch it on and off and check the difference -- if there is any.

With all due respect, taking the belt off is about a 30 second operation. Just do it.

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Got the belt off tonight and took a look. I'm not completely sure what I'm looking for to know if the pulleys are "bad" or not. I took a video of me rolling them, would anyone mind taking a look and letting me know how they seem? I'm not sure that anything I'm hearing here would equate to the noise I hear in the original video I posted, but maybe that's all it takes? Thanks as always for the help!

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That bearing you rotate by hand is gone. Should be basically silent when it is good.

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Thank you so much! So the first and second ones in the video ( the upper and lower idler pulleys )? The tensionser pulley doesn't seem to make noise.

You identified them by yourself: "noisy".

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I have just ordered replacements for the first two ( upper and lower idler pulleys ), I figure I might as well just replace them anyway. The tensioner pulley seems "stiff" to me, but isn't noisy at all, maybe that's how it's supposed to be?

Correct, if it's not running rough or noisy it should be fine. And do not forget to engage the clutch of the AC-compressor to rule that bearing out.

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Looks and sounds to me like the first two you spun need replaced. The first one may be louder and definitely the one causing most of your noise, but the second one isn't far behind. When it spins freely like that, it means that the grease is gone. The third one is quiet, and quickly stops, which means it still has grease.

Any opinion on just replacing the bearings, instead of the complete assembly

Pull the respective pulley... pop off the plastic retaining ring... examine the bearings... bad? Replace with new bearings... press in some grease (by hand) reinstall the plastic retaining ring... reinstall the pulley. Bearings good, upon inspection? Remove the bearings... spray clean the bearings and the pulley... reinstall the bearings... regrease... reinstall the ring... close it up and reinstall the pulley. Go driving.

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You can certainly save some money by doing so. https://burnerscars.blogspot.com/2016/10/how-to-repair-bad-idle-pulley.html

Installed the new upper and lower idler pulleys this weekend and put everything back together. Long story short, the rumble is still there. Maybe a little better, hard to tell. Regardless those 2 pulleys needed switching out anyway so not a complete waste of time. Back to the drawing board, but at least I eliminated 2 of the potential culprits.

Had another chance to revisit this today, the rumbling is almost certainly coming from the alternator. I was able to very this by using a long screwdriver as a "stethoscope" and the noise is far and away loudest when placed on the alternator compared to the waterpump or AC compressor areas. What is my path of least resistance on fixing this? New alternator? New to me alternator? Is it possible to just replace the pulley? I'll be doing this myself so any advice is much appreciated. Here's what I have:

Great you nailed it down. I think you have two options. Refurbish the generator by yourself, there are lots of vids out there. I would do that if you have time. Otherwise buy an excahnge unit and resend you old alternator. For dissambly check this.

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I'm leaning towards replacing just the pulley and hoping that solves the noise issue. Are there other parts of the alternator that might be making the noise, or is it likely that replacing the pulley will solve it?

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If the car is a manual transmission, the alternator will have an OAP (overrunning alternator pulley has a one-way clutch allowing the alternator to coast freely), if it is a Tip trans, it will have a simple fixed pulley. The OAP can develop noise, the simple pulley will not. There are also bearings internal to the alternator which can go bad as well.

Turns out it was the alternator. Guess how I found out? Lesson 1, don't wait too long once you hear the rumbling. Lesson 2, don't skimp on an eBay alternator as a replacement. I should probably be glad that it broke before I got it installed in the car. Ended up buying a new Bosch and everything is working amazingly. Thanks so much to everyone here for helping me navigate this problem from start to finish!

This is what I use, it provides charging possibility and gives you the information from the alternator. Can be switched off.