997S noise above 4000 RPM

[bigscotia10]

I'm getting a weird buzzing noise (buzz/whine) when above 4000 RPM. It's a 997S 1st gen no mods, with about 70k on it. It sounds a bit like the car is struggling at anything past 4000 RPM.. It happens in gear and in neutral. When its hot and cold. if anyone has any ideas of parts I should look at, that may be causing this, please let me know!

 

I'll post a video of the sound in the next couple of days too, so you can hear what it sounds like.

 

Thanks a lot!

[White987S]

All maintenance up to date? Stuff like; plugs, filters, serpt belt, water pump? Any CEL's?

[bigscotia10]

Yep, had a maintenance about 3,000 miles ago and no CEL at the moment. Haven't had a chance to record the noise yet, but will hopefully be able to add that soon.

[Ahsai]

I think the easiest will be to get under the car and use a mechanics stethoscope or long screwdriver to poke around the engine, catalytic converters, heatshield, etc. for the source of the noise while someone revs the engine to 4k.

[bigscotia10]

Yeah thats a good call. I'll do that over the weekend and see what I can find.

[bigscotia10]

I revved up the engine until 4000 RPM, and went behind the car. It actually sounds like it might be a belt noise. It's a high pitched squeal that sticks around at 4000 plus, then goes away once the engine revs are dropped down bellow 4000 RPM again.

[White987S]

When was your 60,000 mile (or 6 year) serpentine belt service done? Check your pulleys too.

[bigscotia10]

The belt looks ok to me. It looks like it was replaced at the last service about 6 months ago. Any tips for what I should look for visually on the pulleys. The plastic is not completely flat and has a slight ridge but I'm not sure if that is normal? I may just swing up to the dealer and compare the pulley and see if mine is any different.

Thanks a lot for the help!

[dphatch]

Could be one or more the bearings in one or more of the pulleys or an alternator bearing. Need to remove air filter housing and the serpentine belt

and spin each of the pulleys and listen. Not unusual for these bearings to go. You can get the whole set from SunCoast or Sunset for acouple hundred bucks. Replace the belt while your at it regardless of your determination of it's condition. $ 30 parts aren't worth

trying to get a few extra miles out of.

Edited December 23, 2014 by dphatch

[White987S]

Could still be the water pump. Only replace with an OE Porsche pump.

[Mijostyn]

Some good advise here. It does sound to me like your belt is slipping. The belt tensioner may be bad. Engine Ears will tell you exactly where the noise is coming from. This is an electronic amplified mechanic's stethoscope and IMHO worth their weight in gold. It will find any rattle or noise.

http://www.amazon.com/Products-steelman-Stethescope-Electronic-Engine/dp/B000WNJ90W If for instance it is your water pump going the noise in the headset will be dramatically louder when you point the directional microphone at the water pump.

If it is your belt slipping then you should replace it as well as figuring out why it is slipping. It could be a bad tensioner or a bad bearing anywhere in the accessory drive. The Engine Ears will tell you which pulley is slipping. If it turns out to be something else altogether then the Engine ears will lead you right to it.

JFP, how often to the tensioners fail??

[bigscotia10]

Thanks all! I haven't had a ton of time to look at it recently, but I did do a quick noise test with someone else revving it. I think it's coming from the alternator pulley... but I'll keep troubleshooting.

 

Is it safe to do the following?

1. Pull out the airbox

2. Take of the belt

3. Rev the engine without the belt on

 

I want to verify the noise is coming from the pulley/belt.. but want to make sure that doing this test won't damage anything?

 

Thanks again for all your help!

[Ahsai]

Yes, it's safe if you run it only briefly, say less than a minute.

[bigscotia10]

Just a quick update.. So I took the belt off and checked all the pulleys.

The tensioner and bottom idler pulley seem fine, and both act exactly the same. The top pulley seems to spin a bit too freely. And the AC compressor pulley has the slightest little bit of play.

So my plan is to replace the top idler pulley (think it needs it either way) and belt, and see if that fixes the issue. If that doesn't, then I'll try running it above 4,000 RPM with the AC on and see if the noise is different/gone... and go from there.

[bigscotia10]

So I replaced the upper pulley and belt. The noise was gone when going above 4000 rpm. Took it for a drive and the noise appeared only when decelerating down past 4000. Then after driving for a while it came back both accelerating over 4000 rpm and decelerating. Any ideas? Same noise with ac on and off.

[Ahsai]

Have you checked the alternator pulley and power steering pump pulley? Yours may have the clutch type that slips when the alternator spins faster than the pulley. I think you may still want to check the noise with the belt off briefly.

Edited January 13, 2015 by Ahsai

[Mijostyn]

Noises like this can be a real pain and they can be very tough to localize. With the Engine Ear you will have your answer in 30 seconds before you waste a lot more money and time replacing parts. This makes the kit an extreme value and I believe a must for anyone who likes to work on their own cars. I think I paid $89 for mine on Amazon. Here are two pictures one with the probe attached. I hardly ever use the probe. Just pointing the microphone around does the trick 99% of the time.

 

 

 

[bigscotia10]

Thank you both.. I order that tool, so I'll give that a shot once it comes.

 

All the other pulleys seemed fine when tested. I'm a little hesitant to run the engine with the belt off, since I need to get it above 4000 to hear the noise, and the engine heats up quickly.. I don't want to cause any damage, but I think I'll give that a shot soon if I still can't find the issue.

 

I started looking around at the clamps too and tightened them all up, just to make sure the exhaust isn't the culprit. Does anyone know where I could fine a diagram that lists all the exhaust clamps? I want to check to make sure there are no hair line cracks in the cramps that could be causing the noise.

 

Thanks a lot!!

[Ahsai]

Here you go http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=997-05-08&section=202-00

 

When you test the alternator pulley, you could try to spin it quickly, then stop the pulley abruptly. The internal armature should still keep spinning.

[bigscotia10]

Thanks for the link! Alternator seems fine when testing it.

 

Checked all the brackets, they all seem fine. I tried using the Engine Ear, no luck so far. I pulled the orange plug to turn the pse on all the time, and I don't think I hear the noise anymore. I definitely heard it when it was turned on via the PSE button and when off. I think next up I'll check all the heat shields.

 

As far as I can tell, it seems to only happen at 3900 - 4100 in each gear. I wonder if something is just changing over in that rev range? Also, any idea what is disabled when the orange PSE plug is pulled? For example, I wonder if it's bypassing something that comes into play around that rev range.

 

The engine ear did help track down an interior noise though, so def a useful tool to have.

[Mijostyn]

Just have somebody rev the engine up to 4000 and point the Engine Ear at the shields. It is either there or it is not. If you did not find the noise with the engine ears you were probably in the wrong vicinity. The trick is the wave the wand slowly around picking the loudest direction repeating this maneuver until you find it. The noise is coming from somewhere. The Engine Ear amplifies sound in a directional manner. There is a learning curve here. If you can't find it by air conduction you use the probe touching various parts following the volume of the signal. 

[bigscotia10]

In case anyone else has a similar issue, it looks like this is due to a broken flap in the PSE or a crack somewhere in the right side of the exhaust.

 

If it's the flap, I think the only option is to replace it, right?

[White987S]

In case anyone else has a similar issue, it looks like this is due to a broken flap in the PSE or a crack somewhere in the right side of the exhaust.

 

If it's the flap, I think the only option is to replace it, right?

Contact Darin at FD Motorsports. He may be able to salvage your PSE with a little surgery, and provide a great sounding exhaust in constant sport mode without drone. And ceramic powder coat a few different colors. Good luck.

 

http://fdmotorsports.net/fister-exhaust-997-one

Edited March 27, 2015 by White987S

[bigscotia10]

Thanks for the heads up White987S, will have a look.

[bigscotia10]

Just an update incase anyone else has this issue. I ended up pulling off both mufflers, and took a closer look. The passenger side one was missing a weld on top of one of the pipes. It looks like it was never actually welded from the factory. And both mufflers had identical cracks on the support braces. These are the braces are that furthest from view, so I hadn't noticed them without taking the muffler off. I took the mufflers to a welding shop and had them weld the straps and non welded pipe. I put them back on, and I think that may have solved the issue.

Edited May 1, 2015 by bigscotia10