Weird whining / whistling sound after IMS replacement - anyone experienced this?

Hi everyone, I have to admit, I’m feeling pretty depressed about this situation. A little over a year ago I bought a 1998 Porsche 911 Carrera 2 Tiptronic. I know many people prefer manuals, but honestly, I don’t really care about that. The price was good, but the main reason I bought the car was the color combination: forest green with a beige interior. It was exactly what I had always wanted, and the car looks amazing. The car was running well, with no real signs of any major issues. I drove it for around 10,000 km and the engine always sounded and felt very healthy. This year I decided to do some bigger maintenance. Oil service, suspension arms, and since the car was already at the mechanic, I also decided to replace the IMS bearing. It was the original double-row IMS bearing, and by the way, it looked completely fine. The car has around 104,000 km. Unfortunately, that is where everything started. After the IMS replacement, a strange whining / whistling noise started coming from the engine area. Since then, many things have been checked and replaced several times. The AOS was replaced, the IMS was changed again, even using three different manufacturers, and the external belt system and pulleys have been checked multiple times. But nothing has solved the noise. My mechanic now says it could possibly be something inside the engine timing system. His theory is that when the IMS was removed, the chains may have loosened slightly, which could have accelerated some hidden issue that was already there. Of course, removing the engine and splitting the case would be extremely expensive and time-consuming, and honestly, I’m quite worried about what else could be found inside. Before this service, the engine had a beautiful sound and ran perfectly. Has anyone here had a similar experience after an IMS replacement? Or does anyone have any idea what could cause this kind of whining / whistling noise?

What a nightmare! It's quite an invasive procedure changing the IMS bearing especially putting the new one back in. It's impossible to diagnose what's happened especially from a description of a sound it's making but I understand you can't really replicate it and we'd need to know roughly where it's coming from. Banging the new one in might have done something at the other end of the IMS shaft where it enters the oil pump housing but I doubt it as we'd have known of this issue before unless someone was particularly heavy handed with it.. It's important to freeze the bearing prior to fitting to reduce the effort required to bang it back in. Someone on here pointed out on here you shouldn't do that because of condensation but in this case the bearing will be covered in oil very quickly so shouldn't matter, I'd definitely freeze it in this case. I'm waffling , I hope you can find out what it is, hopefully it might not be anything to do with the IMS. Best of luck.

Sorry to hear of your problem. My honest opinion - they've bust something inside the engine when they started messing with the (perfectly OK) IMS bearing. This is why is shouldn't be done in situ unless you know the original bearing is goosed, as it's the lesser of 2 evils yanking it out. There's plenty of things that can get damaged internally when doing it. Have they had a listening stick around all the engine bay and underneath to pin point where the noise is coming from? Or has it been a case of just fitting new parts hoping the noise will go away? If it's coming from inside the engine, then get saving as it'll need to come out and be stripped, preferably by someone who knows what they're looking for.

Are there any figures supporting the dual row IMS failure rates...?

Quotes source post: 2812623

I've always been a believer you can't put a figure on something like this or borescore as it's not like a % left the factory with that fault. It's an ongoing thing. ........but Porsche claimed when there was the US lawsuit 0.8% dual row & 8% single row. You could also argue that all those destined to go have gone. When mine was changed at 170k I was told there was a very slight amount of wear but very minimal and ok.

Thanks for all the replies, I am not the one who is scared by IMS failures as I know how low % it affetcs, but I felt that "why not" when it was there...maybe it was better to not touch it. I asked some AI what it could be, and it pointed me to a thread here with similar issue, https://911uk.com/porsche/whining-noise.94743/ Also it is pointing to few things that may be the issue 1. IMS chain tensioner – removed during IMS replacement, may have been reinstalled incorrectly or is faulty. Accessible from outside the engine. 2. Chain guide installed upside down – easy mistake to make during IMS replacement, causes exactly this type of RPM-dependent noise. 3. VarioCam unit – oil pressure activated, which would explain why the noise appears only after a minute or two of running. Anything makes any sense?

OP, was this mechanic employed by a Porsche specialist...?

1. Was your chain tensioner removed when the job was done? Not normal to do that. 2. Chain guide can only be removed / installed by opening up the engine. 3. Variocam unit is electrically operated / activated. Like I asked earlier, has the area the noise is coming from been pin pointed by your mechanic?

Quotes source post: 2812684

I dont know. I am not talking to mechanic, my friend who is the chief of official WV service centrum here is dealing with it. The mechanic worked on his 996 as well for years. I will have to go there and record the noise - maybe it will be helpful.

Without pin pointing it's location you're knackered.

I doubt it's anything to do with the vario cam or chains as this would cause more problems than a noise. It could be that the torque converter has been knocked out of balance or not bolted back on to it's original balanced place to the flywheel. The pair should be marked before disassembly and put back in the same place.

Sounds possible.

okey, will try to find exact spot. How common is that you really have to take the engine apart to fix something like that?

Quotes source post: 2812721

If you start messing with any internal engine parts from outside the engine, then yes, there's a good chance you may have to take the engine part. My opinion - changing an ims bearing in situ is suicide. The force exerted on pulling the bearing out and pressing another in is greater than the strength of some of the components connected to it. Then you also have the issues of it not being pressed in correctly (square) too. On top of that you have issues around tolerances of the shaft and bearing - too tight and the bearing's wear will be accelerated. These last 2 points are relevant for any frictionless ball/roller bearing that is being pressed into position. This may all be ok fitting something like a wheel bearing, but on such a critical internal engine component, not for me.

I'm not even sure you can press the IMS bearing in can you? The normal procedure is too thump it in using the tool in the kit. It's not good whatever , I did it on my old 2.7 Boxster but when I had the engine out of the 3.4 C2 this year, I didn't even pull the cover off , not leaking so I left it alone as well as the RMS.

I totally get what Alex is saying and about 99% of so called specialists bash the bearing in with a lump hammer, but it doesn’t have to be like that . If you freeze the bearing overnight it can be just carefully taped in even the double row goes in easily. It’s a job that needs care and attention not too be rushed. most just don’t have time to do right and end up causing damage.

When I was a young Toolmaker I got the World's biggest bollocking off one of the older Toolmakers for installing a bearing in a press tool knocking it in. Words were something like - "It's not a f***in' nail you f***in' Ham-booner!!" I still use that term (Ham-booner) today. I think the actual translation from Lancashire hairy arsed Engineer to English is Ham fisted Bonehead.

Quotes source post: 750277

I just searched the site for ham-booner and this came up

Oh wow... for years, I read all over the internet how everyone is replacing the IMS on their 996 like it is the most common and right thing to do and once I do it, it is suddenly the most risky thing that can get critical Great. So the mechanic could really damage something while putting the new one in? I remmeber seeing tons of videos on YT how people changing the IMS and it looked like it is smooth job, with no force needed.

Yes, they can damage something putting it in. Not worth the risk unless you KNOW your's is beyond help and about to fail.

Quotes source post: 2812789

And this surprises me as never I saw aonyone write about this, everyone is always like "I preventively changed it - because why not. Seems like no matter what when car is at big service people do this.

Here's an interesting read from the owner of famous Porsche engine builder Hartech: Post in thread 'Ims advice please and help' 23 May 2018 The difficulty here is that some bearings were fitted a bit tighter than others (usual manufacturers tolerance build up) and these generated more minute running in metallic particles that mixed with grease and formed grinding paste that prematurely damaged some bearings. Most however were OK. The grease gradually escaped because when hot it is very thin and at that point it depends how worn the seal is as to how much engine oil can seep back in to protect the bearing. This is why they either seem to fail early (under 45K) or last well over 100K. Unfortunately the small spindle shaft... bazhart

Both my 1997 Boxster and 1999 996.1 still have their original double-row IMS bearings. When I had the clutches replaced, I had the RMS done at the same time, but after a lot of research I decided not to replace the IMS bearings. Both cars were already over 200k miles, and the general consensus I found was that the double-row bearing is a robust design. If it has survived that kind of mileage without issue, it’s generally likely to continue doing so. One of the arguments that made sense to me was that replacing the bearing means fitting a new component into a housing that may have developed wear over many years. The original bearing, on the other hand, has worn in together with the shaft and housing and is already running within those established tolerances. I’m not saying replacement is wrong, just that in the case of a proven, high-mileage double-row IMS, I wasn’t convinced there was enough benefit to justify disturbing a bearing that had already demonstrated its reliability over 200k miles.

Quotes source post: 2812796

OK great this sadly wont help me much now.... I know that double row should be more durable, but you never know it is 27 years old component so from what I get as general consesus is - replacing it for new is always more likely be failure proof thatn leaving old one in.

Quotes source post: 810735

Not true. The issue with IMS bearing failures is infant mortality, not wear. Any wear that is seen with the bearing is usally down to the effects that cause infant mortality too. I wrote about it here around 12 years ago (I would say the wear failure position on the below graph would likely be well over 200k):

Especially pertinent to the 98 and 99 cars.

I wonder if the noise you can here is the bearing spinning in the case ! Do you know which bearing was fitted? Probably not that but just trying to think what might have happened. What Hooner said about the tip box is more likely.

A bit of a punt, but the air con compressor can whine if it's low on gas...it will also only start to whine after a period of time and as the compressor is driven by the engine, the sound will change with RPM. Have you tried turning off the A/C (so the compressor clutch disengages) and if so, does the sound immediately stop?

Thank you for all your input. I will hopefully visit the mechanic on Friday and will record the noise and ask him about everything

You really need to identify where the sound is coming from. Easy to do with a piece of hose or a stick.

Does it sound like this?

[Image-only or quote-only post; no author-written text.] https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f923.png

Whilst harsh on the OP and unhelpful, for others reading this in future, this is why you don't go changing dual row IMSBs on cars built before 2001 model year without good reason. (In 2001 MY for 3.4l C2 or C4 up to engine number 661 14164 is dual row). Most that come out are sound and there is the potential for failure if the job isn't done correctly... If when you have the 'box out it is leaking oil or has play, then do it (and the main seal), otherwise leave well alone. Now, single row bearings... Documented higher failure risk but still seem to be concentrated to early life failures. Might be considered more of a 'whilst you are in there job' if the 'box is out, but only change the bearing, no need to go to flash ceramics or oil fed versions that cost a fortune. A single row IMSB is a common size and cost about £5 from a bearing distributor.

Box off. Check for play. Remove seal. Box back on. That should be standard protocol.

I had an EPS IMS kit fitted 2 years ago on my 2002 996 C4 and I too have a whistle on acceleration and higher speeds that I am pretty sure wasn’t there before. I have lived with it and got used to it I guess.