Xantia engine area humming noise (1.9TD)

[Deacon]

Hello,

The last week or so I started hearing some humming noise from the engine area. I can hear it from inside the car and a bit when outside where it doesn't seem to be coming from the alternator. The sound appears to change to a higher pitch when I rev the engine, but not by much.

The noise could be heard some time (and not always) after a cold start, not immediately, maybe after 3 or 4 minutes of driving. If I drive a lot and the engine really warms, then the noise disappears.

Immediately after engine start nothing is heard, but if I turn on the a/c compressor the noise appears, and when I turn off the a/c compressor, the noise remains, so I am not sure what to think now... Is it caused from the cold weather? It's cold here, - 8 C in the morning to 3 or 4 C during the day...

Here's a video of the noise that I recorded. Listen to the background humming or whining. It gets a bit louder after revving. For one I am sure that it doesn't come from the hydraulic pump and alternator.



The engine has a 5w40 oil and filters changed 1200km ago, coolant changed a few months ago and the suspension is well maintained.

[white exec]

The heavy bass thrumming sounds like air induction, or exhaust.
Check air filter?

[ksanturion10]

Damper pulley?

[moizeau]

Whip the aux belt off and see if it remains.

[Deacon]

@white exec, you mean the diesel knock noise after the revving? I think the phone's microphone exaggerated the sound a bit. Sounds normal from the cabin.

I will check the aux belt. But I suspect some of the pulleys to be making the sound due to the cold. The damper pulley was changed around 20 000 km ago as well as tensioner and belts and all the rest of the pulleys. Yesterday the car didn't make a sound when I drove home and the weather was warmer. I think I'll wait for the weather to warm up and see how it goes. If the sound persist, I guess I'd go to the mechanic, desconnect the aux belt and try to isolate the noise.

[white exec]

I wasn't sure which aspect of the sound was the problem.
The heavy thrummm sounded loudest, but, as you say, maybe exaggerated by the phone.
Tell us more...

[Deacon]

So today it was 15 degr C. No sign of that sound. The sound is hard to describe but imagine the sound the "Conjecteur" is making, sry don't know the English word, but make it seem continuous like from a bearing. I give it to some of the pulleys not liking the cold hehe. I will keep my ears open. Hopefully will go away as the weather warms up.

[white exec]

Still unsure which noise exactly.
You can test whether it is belt noise by carefully squirting some water (nothing else, and NOT wd40) at the running surface of a belt, to see if it affects the sound. Do just one belt at a time...!

[Sharkie]

Only way to be sure is to remove the belt and check each of the pulleys and rollers.
Sounds like belt wearing on metal, might be from failing roller that tilts belt sideways. Look for ground up belt bits in area.