Whining/Screeching Noise

wstring · 11:24 AM

Need help diagnosing a very loud whining/screeching noise coming from the engine compartment in a 2003 Boxster S. 5 speed triptronic.

Symptoms: Noise starts after the engine has warmed up (approx. 8 miles or 10 min) after initial cold start. Noise is consistent in park, neutral or drive. Noise does not change with manipulation of steering or A/C. With car in park or neutral noise does not change with throttle response. Noise disappears when throttle/accelerator is depressed (car is accelerating) but returns after reaching any cruising speed. Transmission in manual mode. There is absolutely no vibration/engine knock/or other unusual sound or feel while driving.

What it shouldn't be: IMS bearings replaced with retrofit kit 30K miles ago by Porsche dealer. Water pump replaced 1K miles ago by Porsche certified mechanic. Serpentine belt, idler pulleys replaced 10 miles ago. Belt had a small groove on inside edge. Tensioner pulley has not been replaced (didn't have the part on hand at the time the idlers were replaced). Local mechanic did the work (which cost me $700 dollars only to drive out with the same noise I drove in with). The local mech now thinks the noise is coming form the drive shaft (using the same stethoscope that told him it was an idler pulley).

Looking for a second opinion. (other than I need a new mechanic?) The closet Porsche dealer is 250 miles.

A couple more details about that noise. It starts as a light chirping noise and then after a few minutes it is continuous. Also I just had the oil and filter replaced when the idlers were replaced and there and there was no evidence of metallic or plastic material. There was 4300 miles on that oil and filter.

Any help would be appreciated.

Dmitry at Pelican Parts · 04-09-2018, 01:11 PM

Hello and welcome to the forum! Is there any way for you record the sound? - it may be beneficial to our community to hear it to help diagnose the issue. I'm also including a link below to our site's DIY tech articles on your Boxster.

Boxster DIY Tech Articles

wstring · 04-09-2018, 04:44 PM

Thanks for the reply. I will try to get a recording. In the meantime i notice that if i pull the oil stick with engine running there is a sucking noise. Feels like a vacum is being created in the engine block. Also the oil cap will not come off with engine running. Obviously not normal but no check engine light to indicate any issues.

BoxsterSteve · 04-09-2018, 04:49 PM

Just a WAG... screeching sounds like symptoms of a failing/failed AOS.
From your description you have enough crankcase vacuum that you can’t remove the oil filler cap.
Don’t run it or drive it.
If it pulls enough engine oil through, you’ll hydrolock the engine.

wstring · 04-09-2018, 06:40 PM

As soon as I figure out how to insert a recoding I will. Did notice a few more things that may help figure this out though. RPMs at idle is 900. Flucuates slightly when I pull oil stick. Flucuates severly when I remove oil cap. However the whinning noise ceases when i pull either. The noise must be coming from air being sucked in around a seal? White cloth over both exhaust no oil residue. No white smoke. Oil level normal.

Steam Driver · Steam Driver's Garage

I don’t have experience with the engine in question but I think the previously mentioned air/oil separatoris VERY likely the issue. Our 2011 GTI did exactly that and it was the AOS. Not hard to swap on the VW, I don’t know about the Boxster.

wstring · 04-11-2018, 06:22 AM

So based on all I read and you guys input here, I had my indy mech order a new AOS and hoses and elbow. Car starting blowing white smoke which convinced me we were on the right track with the diagnoses. The mech mentioned something about may needing to pull the oil pan and check some "lower" parts associated with the AOS system.? Does this make sense to anyone out there and if so what parts would that be? Thanks again for your help.

mikefocke · 04-11-2018, 07:19 AM

Why would you pull the oil pan? To check for debris, to clean it out, to access oil pumps and oil pickups. But AOS? Doesn't make sense to me. AOSs fail with age generally and not typically as the result of some other failure.

You take off the right rear wheel to gain access to the AOS and it is a most difficult install. Especially for a first timer. But not so bad for someone who has done a few and has the right tools.

Use a Porsche AOS, not aftermarket. And save any warranty paperwork because even stock ones can fail early.

What I've seen done is look at the air intake and throttle body as that is where a failing AOS dumps oil and it could need a good cleaning.