new engine resonance sort of sound

[taylora]

hi
wondering if anyone can suggest what the issue might be before i have to drag the car off to be looked over properly by someone with more oil in their veins than me.

so its 2007/50k miles saloon.
and there is a sort of resonance/whine at certain revs. i first noticed it not long after getting the oil cooler pipes change -but that could be cooincidence. its not loud but its my car and i notice it! even if the missus seems to think i'm talking rubbish again.

the noise it seems to build with revs. but but comes and goes very predictably depending on the revs and temperature.
eg. starts at 1500rpm when cold, but changes to 2000 or so when warm and seems louder. but is gone by 2200 or so. and over 3000 it might be back but you can't hear it over the racket of the rest of the v8.


i can hear only hear it inside the car. not loud enough to noitce outside, and does it in all gears irrespective of clutch in/out and load, eg moving slowly through 2krpm in 6th or fast in first or down through the revs in 3rd.

apart from the noise - which i'll try and record tomorrow - its all fine. no apparent rubbing of any belts, no misfire, vibration, warning lights, or untoward rattlings, got a nice kick at 5k.

as its a sort of resonance sound and specific revs, any idea if it could be something like a belt drive, oil pump or something?

thanks in advance

alistair.

[MikeFish]

Did you use OEM oil cooler pipes or did you get the Forge oil cooler?

[taylora]

audi parts all the way - or so the bill says.

[TonyHayers]

Sure it's not just the normal whine from being chain driven?

[rwilsonrs4]

well you may have a noisy aux belt tensioner possibly , but i think its likely the normal noise from the timing chains , its a different set up totally to the S4 /Q5 and sounds unique, they arealso at the rear of the engine right next to the bulkhead so more likely to be noticed in the cabin i dont hear mine any more as the supercharger is noticably louder

[taylora]

hi
so had a good poke about this morning. i don't think its the normal chain noise, or anything at the back of the engine.

i'm pretty sure now that its somehow connected to the oil cooler pipes.

if i set the engine to a speed where the noise can be heard using my hi-tech adjustment device (broomstick on the throttle through the window)th and then use a socket set to put a bit of pressure on the pipe above the cooler then it seems to go away.
i'm guessing - and from the suggestion about what type of oil cooler, that somewhere behind the bumper there is very little clearance and its somehow leaning against something firm which is transferring the sound into the cabin.
i might try and see if i can losen/tighten the bolts through the grill, otherwise i'd guess its bumper off to see how the routing has worked.

a.

[Audi Pardner]

hi
so had a good poke about this morning. i don't think its the normal chain noise, or anything at the back of the engine.

i'm pretty sure now that its somehow connected to the oil cooler pipes.

if i set the engine to a speed where the noise can be heard using my hi-tech adjustment device (broomstick on the throttle through the window)th and then use a socket set to put a bit of pressure on the pipe above the cooler then it seems to go away.
i'm guessing - and from the suggestion about what type of oil cooler, that somewhere behind the bumper there is very little clearance and its somehow leaning against something firm which is transferring the sound into the cabin.
i might try and see if i can losen/tighten the bolts through the grill, otherwise i'd guess its bumper off to see how the routing has worked.

a.

I'm not sure the cooler could get close enough to anything to vibrate. The mounting lugs space it away from the rad behind and it comes nowhere near the bumper/spoiler, so unless the mechanic has routed the pipes wrongly (which would be difficult to do) it's unlikely to be the cause. Worth checking out though, even if it's a pain removing the bumper. Good luck.

[MikeFish]

The reason I asked is because the forge oil cooler originally came with some bolts that were slightly too long and caused the sort of resonance you are talking about so entirely possible to cause it but not sure just changing the pipes will do it unless they are touching something they shouldn't be.

[adsgreen]

The pipes have rubber spacers that need to be cable tied into position (there was a tech note about it to dealers). If not located correct the pipes can rub...
Might not be the exact cause but certainly a possibility.
I think that there are also rubber spacers/washers in the installation - maybe missing, too tightly secured or not torqued correctly.