Strange noise coming from timing belt area

Applesauce · Post by **Applesauce** » 28 Oct 2021, 22:54

My 850 is making this whirring humming noise from the front of the engine.

Some background info:
The noise started after I took the head off to replace valve stem seals. After putting it back together, I did a full timing belt service with genuine volvo and oem parts.

I already ran the engine with the serpentine belt off and verified that the noise is coming from inside the timing cover.
I also ran it without the timing covers and the noise was a bit quieter but it was still there.

Here is a link to a video I recorded of the engine running and making the noise. https://youtube.com/shorts/HWCRQO_3PkQ?feature=share

Post by **bmdubya1198** » 28 Oct 2021, 23:25

It's kind of hard to hear on the video, but I can make out a strange noise. Is the tensioner set properly? It should be a hydraulic tensioner on that car, so it's unlikely to be an issue being that they're self-adjusting. It wouldn't be a bad idea to check to make sure that there isn't too little deflection on the belt when you press down on it between the cam pulleys.
Have you checked to make sure the plastic covers behind the belt are not rubbing on anything? They can get weak and oil-soaked over time and begin to rub on the belt or pulleys.

Applesauce · Post by **Applesauce** » 28 Oct 2021, 23:57

the tensioner seems to set properly. I can take a video of me poking around the belt with the engine off to show what it looks like. As for the covers, im confident its not the upper cover or the timing belt cover rubbing on anything as there is no difference in The noise with them on or off. As for the plastic cover behind the belt and pulleys, I'll have to double check that one. I'll also post a video of the engine running the with the covers off. When I get a chance.

Applesauce · Post by **Applesauce** » 29 Oct 2021, 14:45

bmdubya1198 wrote: ↑28 Oct 2021, 23:25 It's kind of hard to hear on the video, but I can make out a strange noise. Is the tensioner set properly? It should be a hydraulic tensioner on that car, so it's unlikely to be an issue being that they're self-adjusting. It wouldn't be a bad idea to check to make sure that there isn't too little deflection on the belt when you press down on it between the cam pulleys.
Have you checked to make sure the plastic covers behind the belt are not rubbing on anything? They can get weak and oil-soaked over time and begin to rub on the belt or pulleys.

Ok so I've recorded some more footage.
And i think i might be onto something now.

Here is a video of my poking at the belt checking for proper tension. I noticed I could move the belt with my fingers witch seemed odd. I also found I could turn the idler pulley with my fingers. But if I turn the engine over clockwise it tightens up. Is this normal? It seemed to have good tension otherwise.

Here is a video of the engine running with the covers off.

And here is a video with the engine running (covers off) but strangely the noise seems to have gone away! using a vaccun hose as a stethoscope, i probed that plastic back cover you mentioned and I think I might have tweeked it or something. Take a listen.

Post by **bmdubya1198** » 29 Oct 2021, 18:08

I think that cover might have been rubbing and you tweaked it enough to clear. I definitely hear the difference between the two videos!
The belt is usually able to move a little bit on the pulleys, so as long as it's not super loose you should be fine. Deflection looks good, nothing excessive. As long as you pulled the pin from the tensioner piston (which you must have if the belt isn't completely loose) then I think you might have fixed your noise.

Applesauce · Post by **Applesauce** » 29 Oct 2021, 18:59

bmdubya1198 wrote: ↑29 Oct 2021, 18:08 I think that cover might have been rubbing and you tweaked it enough to clear. I definitely hear the difference between the two videos!
The belt is usually able to move a little bit on the pulleys, so as long as it's not super loose you should be fine. Deflection looks good, nothing excessive. As long as you pulled the pin from the tensioner piston (which you must have if the belt isn't completely loose) then I think you might have fixed your noise.

Well okay! That's releiving. I thought I broke something for bit there. I'm gonna do some more testing and listening; make sure its all good. Thanks for your help!

Post by **bmdubya1198** » 29 Oct 2021, 22:34

Obviously it's just a visual from the video, but everything LOOKS to be installed correctly. I think you're probably good to go with the installation, just dealing with some minor annoyances with old engines!