S80 T6 strange noise on the Timing Belt

nberga · Post by **nberga** » 06 Jul 2025, 01:20

Hi,

Just changed my Timing Belt and Water Pump, everything weny smooth, checked and re ckecked timing, both upper marks and crank marks, they lined perfectly after rotating the engine 4 times.
Adjusted the tensioner on the middle with the specs for my country

Finish the job, started the car, and i have this strange noise....

What do you think?

Vova585 · Post by **Vova585** » 06 Jul 2025, 17:49

Hard to say without being close to the car with stethoscope. I would first question quality of the tensioner roller and idler pulley(hope you replaced both with quality items). If that was checked and looks good, I would make sure all the surrounding metal plates(covers) properly tensioner so no vibration. Thirdly- was the serpentine belt or rollers or both changed? Sometimes serpe time belt can be installed in incorrectly so would check diagram for that as well.
Sorry, never had 2.9 engine(at least o assume ot is 2.9 6cyl)

On the other thought..have you checked your steering fluid level..

nberga · Post by **nberga** » 07 Jul 2025, 02:19

Vova585 wrote: ↑06 Jul 2025, 17:49 Hard to say without being close to the car with stethoscope. I would first question quality of the tensioner roller and idler pulley(hope you replaced both with quality items). If that was checked and looks good, I would make sure all the surrounding metal plates(covers) properly tensioner so no vibration. Thirdly- was the serpentine belt or rollers or both changed? Sometimes serpe time belt can be installed in incorrectly so would check diagram for that as well.
Sorry, never had 2.9 engine(at least o assume ot is 2.9 6cyl)

On the other thought..have you checked your steering fluid level..

Vova585, thanks for the answer, both Tensioner and idler were from GK, the same for the Timing Belt, was the kit they have for the 2.9L.

The Serpentine is brand new like the tensioner also, from Continental, but was installed some weeks ago and never had the noise, only now was the Timing belt and water pump changed.

The covers were remove for the video and also to delete any possible resonations from there, so no covers to make noise.

The fluid level was topped yes but now that you mentioned never checked after the engine running, will check it.

Cees Klumper · Post by **Cees Klumper** » 13 Jul 2025, 10:14

x2 on the power steering fluid, sounds like it's drawing air.

nberga · Post by **nberga** » 14 Jul 2025, 00:12

Cees Klumper wrote: ↑13 Jul 2025, 10:14 x2 on the power steering fluid, sounds like it's drawing air.

Already checked and it's top level on cold.

Cees Klumper · Post by **Cees Klumper** » 13 Aug 2025, 23:14

Oddest thing!

Just this weekend I also replaced my timing belt, water pump, serpentine belt and all tensioners and pullies and now I have the exact same sound on my 2002 T6! What are the odds. I verified that the timing is spot on, no trouble codes, engine is as smooth as ever and pulls strong etc. Was planning to remove the plastic covers as the most likely culprit in the coming days but you already did that. All parts from Skandix Germany, and exactly same dimensions etc as what came out. Tension on the timing belt set as per guidance for the temperature.

Could it be the rear plastic cover perhaps? I had to loosen that to swap out the water pump.

Cees Klumper · Post by **Cees Klumper** » 24 Aug 2025, 09:16

Small update is the noise is now less but still there. It is NOT present at cold startup, nor when just slightly increasing RPM. So, only at warm idle now and disappears at normal driving rpms.
This is still bugging me so I will tear it all back down in the coming week or so. Everything was super quiet before I changed the belts and pullies/tensioners. Hate to think brand new parts would cause this noise and still think it could be one of the plastic or metal covers. I did check the pullies and tensioners before installing, they seemed perfectly ok but of course can't spin them by hand under the type of tension and at the speed the engine does. I tried pinpointing the location with a surrogate stethoscope but to no avail.

Cees Klumper · Post by **Cees Klumper** » 30 Aug 2025, 07:59

Update: today I decided to dive into trying to figure out why my S80 T6 is making this noise, immediately after I replaced timing and serpentine belt, water pump and all tensioners and pullies. First I removed the serpentine belt to rule out that whole section - no change in the noise. So then I moved onto the timing belt etc.
I first removed the plastic cover - no change.
I then decided to run the engine without any covers. To my surprise, the timing belt is 'wandering' on the pullies, from side to side. It appeared to be the worst on the tensioner pulley, so I decided to remove and inspect that. There was just a little bit of 'compacted grease' in one spot - some caked on oil thingie must have fallen onto it when I installed it without my noticing it. I carefully inspected the tensioner and idler pullleys, comparing to the old ones I took off (Volvo branded) and looking for any clues as to whether one of the pulleys maybe was not 'straight'. Both were ultra smooth and no indication of any problem. I contemplated putting the old ones back in but decided against that. Put it all back together and took this video:

As you can see, the 'wandering' is not that significant - it appears to be a bit better after I cleaned that little bit of dirt off the tensioner pulley. I also think the noise I am hearing is caused by this wandering behavior, as it is likely causing some friction as the belt moves across the toothed pulleys.

I then decided to do a google search for 'why is my timing belt not running straight' and lo and behold most top hits were about Volvos, and led to discussions on this here site. Most comments attribute the wandering to the brand of belt used: for example, Gates branded belts according to the comments tend to wander, while Contitech belts do not. I imagine Volvo branded belts also do not, since that is what I replaced a few weeks ago. The most comforting comment in these threads on this site was from Robert (rspi) that he sees this wandering a lot and don't worry about it. The belt I installed is a Hutchinson branded one.

I need to take a 200 mile trip next weekend and am worried about breaking down (well, about destroying the engine actually if the timing belt breaks, of course). I don't have time between now and then to get and install a different belt. But, I can also take my Volvo C70 which is running beautifully, and try a different belt (and probably I would get new tensioner and idler pulley just to be sure, and likely also a new water pump, although the one I just installed is the proper Aisin one) after I get back from my trip. I got all of these parts at Skandix, not some discount Ebay special.

Should I worry or stop worrying about this OR try and eliminate the wandering/noise? The engine runs super smooth and strong and there are no particular wear marks on the timing belt. So far I've done about 250 miles on this new setup. The noise seemed a bit stronger in the beginning, now it's quieter. Grateful for any suggestions.