Engine Bay Whine

[Petoir]

Hi,

Looking for some help and advice. I'm always nervous after taking the RS4 into Audi - sounds ironic I know, but after this occasion I think I might get it serviced by a specialist next time around.

Car's just had the 40k belt change last week. A new sound has developed since, I don't know exactly what is done for the belt change, but I presume the engine comes out?

Basically, if I accelerate in 4th or 5th from low revs 1/1500 to boost, post 3 / 3500 to 5000 revs staying in 4th or 5th, a whining sound comes from the engine bay. Given the revs I presume it's the turbos, but it's not quite the sweet whine you normally get, there is a definite grind / hiss that wasn't there before last week and it's pretty noticeable in the cabin. Kind of sounds like two dinner plates rubbing together.

Could be the turbos?? Could be the new belts slipping???

Car performs well, no hesitation and no noticeable sounds or problems in other gears, through the rev range.

Warranty is up in Sept and I will be taking it back to Audi this week - but any tips / help on anything similar would be appreciated. Car is standard apart from Milltek Catback. (Stage 1 coming in Oct.)

Cheers,

Pete

[RED_ROCKET]

It may be the clutch, release bearing??

I seem to get the same sound..

[JAMES]

the engine doesn't come out as far as i am aware.
i dont think the cam belts are slipping or you would have heard a crash,(then its all over for the engine).these belts are toothed and must not slip or break as the engine components will colide together.which is why the 40k belt change is very important.a fan belt would slip in all gears.
maybe a turbo pipe is loose,but seems strange its only in 4th and 5th.
sorry cant think of anything.

[RED_ROCKET]

it may be the flywheel bearing>>

[Golich]

This is a tricky one without hearing it. But as you say it wasn't there before you had the timing belt replaced. The 4th and 5th gear could be relevant to the turbos as if you are accelerating from a low speed in a high gear the engine rpm will be low and the boost pressure sustained for a relatively long period than say accelerating quickly up though the box. The low rpm means reduced noise so you stand a better chance of hearing other anomalies. It’s anyone’s guess on this forum.

One thing you can do is to have a look at the rotating components at the very front of the engine. i.e. by the radiator. Check that none of the alternator/power steering belts etc have come loose or the fan is rubbing on something such a hose or intake pipe. With my last S4 some Muppet had clearly changed the DVs with a little too much force on the plastic pipes from the intercooler up to the TBB. This snapped the plastic pipe clamps and judging from the wear on the fan the fan was obvious touching the pipes under some condition of engine load as it was clear when the engine was idling. However the sloppy engine mounts of our cars mean that there is quite a bit of movement under acceleration and deceleration.

PS the entire front end of the car is removed to access the timing belt which resides right at the front of the engine. The service includes removing and replacing the belt tensioner pulley and the water pump if memory serves me right. If the belt is not tensioned correctly it is not uncommon on other cars for the belt to rattle off the plastic cover. I have experienced this and it sounds like the big end bearing is knackered!! On the other hand, if the belt is too tight it can cause a strange whine which changes with engine rpm which is noticeable upon free reving at idle.