Whooshing/hissing air type noise from dash area over 30mph

[AllHailKingVolvo]

Hi all,
I collected my 240 estate from my local garage today after they fitted a new rear main seal and input shaft spigot bearing.

The car drives fine, but I'm noticing a whooshing/hissing noise from the dash area at over 30mph...the garage have had the car for several days so I can't remember if it was there previously. Either way, my 740 doesn't make that sort of noise, so I presume it's something I need to sort out.

It doesn't change when I dip the clutch, and seems to be specifically related to speed not rpm. It doesn't change when loading either side of the car during cornering or abate/change when I hit the brakes, other than getting gradually quieter as the car slows down.

Altering the heater controls/air redirection flaps doesn't seem to have an effect either.

Any ideas would be very welcome!

[honestjoe]

Hi..i"ll make a start on this...Could it be the gear lever gaiter/rubber sleeve come adrift?..a lot of noise would be produced if that was the case.I know this sounds stupid but is the passenger door shut tight..Same sort of sound produced.and just for other readers was it the engine rear seal replaced?..trying to imagine where the work was carried out on the car..Hope you get to the bottom of this..regards hj.

[AllHailKingVolvo]

Originally Posted by honestjoe

Hi..i"ll make a start on this...Could it be the gear lever gaiter/rubber sleeve come adrift?..a lot of noise would be produced if that was the case.I know this sounds stupid but is the passenger door shut tight..Same sort of sound produced.and just for other readers was it the engine rear seal replaced?..trying to imagine where the work was carried out on the car..Hope you get to the bottom of this..regards hj.

Yes indeed, it was the rear main that was replaced. I'll check the gaiter, I didn't think of that!

[Stephen Edwin]

Originally Posted by honestjoe

Hi..i"ll make a start on this...Could it be the gear lever gaiter/rubber sleeve come adrift?..a lot of noise would be produced if that was the case.I know this sounds stupid but is the passenger door shut tight..Same sort of sound produced.and just for other readers was it the engine rear seal replaced?..trying to imagine where the work was carried out on the car..Hope you get to the bottom of this..regards hj.

That sounds (sorry....) very likely.

It reminds me of the Austin Somerset one fine summer making strange noises. A garage diagnosed it. The car was being driven past fence posts with the front windows wound down.

.

[AllHailKingVolvo]

I've gone over it with a fine toothed comb and can't find and bungs, gaiters, seals or soundproofing loose or misplaced.

One thing I DID spot though is that right at the base of the NSF brake disc (where the flat bit meets the hub bit) there is a fresh, bright silver groove worn, as if a stone or some other debris has become trapped in there and has been scraping away at the disc. This could easily be the noise I'm hearing. I'm going to whip the wheel off at the weekend and do some investigating. I may well order a set of pads for it too whilst I'm at it. Two birds and all that!

[Nicholas Lewin]

I also wondered whether the rubber flap seals on the two centre dashboard air vents had perished (and lost their efficacy) and as they are force-fed fresh air from the below-windscreen grille are always getting a supply of fresh air. Worth a check if your brake issue proves non-conclusive?

[AllHailKingVolvo]

Originally Posted by Nicholas Lewin

I also wondered whether the rubber flap seals on the two centre dashboard air vents had perished (and lost their efficacy) and as they are force-fed fresh air from the below-windscreen grille are always getting a supply of fresh air. Worth a check if your brake issue proves non-conclusive?

Good thinking, I would never have thought of that! The car has a reasonably high degree of rubber degradation (all the suspension bushes have had to be changed, and engine and gearbox mounts are next on my list), so there's every chance that the rubber flap seals have expired too. I'll investigate asap!

[Clifford Pope]

A coincidence though that it suddenly happened after removing the gearbox?

I'd still check the fit of the gearlever grommet to the metalwork, and that the thick rubber insulation packing has been correctly put back in place.

As an example of how much noise can come from a small gap in that area, just try pinching the boot round the gearlever while driving along. If there is a tiny gap, slide the boot down and put a turn of insulating tape round the lever.

And of course they've disturbed it again having to re-do the flywheel

[AllHailKingVolvo]

Originally Posted by Clifford Pope

A coincidence though that it suddenly happened after removing the gearbox?

I'd still check the fit of the gearlever grommet to the metalwork, and that the thick rubber insulation packing has been correctly put back in place.

As an example of how much noise can come from a small gap in that area, just try pinching the boot round the gearlever while driving along. If there is a tiny gap, slide the boot down and put a turn of insulating tape round the lever.

And of course they've disturbed it again having to re-do the flywheel

This is indeed where the noise is coming from! If I push the carpet down ahead of the gear lever and gaiter, the noise vanishes. I'll get in there with some soundproofing methinks. At least I now know it's nothing serious!