V70 TDI ...booming note during acceleration

[SilverSwede]

Checked intercooler pipes and other air hoses - all ok. Air filter/ airbox no leaks.

It's a boomy intake noise like when you have the lid off the air box and no filter in an old Escort mkII - this is the only way I can describe it...

This sound seems to have got louder since engine mounts have been replaced but engine running fine otherwise.

Has anybody any suggestions what may be causing it?

Many thanks in advance.

[brickman]

Mounts backwards? Front and rear mount look very similar but wrong way around will cause excess vibration into subframe under load.

I posted about the same a few months ago as couldn't work out which way they went. Only source for one of the mounts is skandix, got both from there, quality very meh, so barely much difference from my 300k old mounts.

Note. Does the rubber bung under gearbox touch the subframe? Mine does with new and old mounts, but not sure it's meant to touch subframe all the time. That would also be a source of excess noise

[SilverSwede]

Yes I saw your useful post about mounts and made sure the Scandix ones and FRF (or PFS?) ones were marked according to their positions under the engine. Scandix great service btw - 4 days from Germany!
Rubber bung now 5mm clear from subframe and vibration much better - a correctly-timed recon fuelpump should get things near perfect.

As I say, this is more of an irritating boom/suction-type noise rather than vibration, and I'm hoping it's not sucking **** in from the atmosphere from some as-yet unknown location on the engine! The breather on top of the engine is the latest suspect as seems a little oily and loose. Just need to figure how to get it off?

[brickman]

Originally Posted by SilverSwede

Yes I saw your useful post about mounts and made sure the Scandix ones and FRF (or PFS?) ones were marked according to their positions under the engine. Scandix great service btw - 4 days from Germany!
Rubber bung now 5mm clear from subframe and vibration much better - a correctly-timed recon fuelpump should get things near perfect.

As I say, this is more of an irritating boom/suction-type noise rather than vibration, and I'm hoping it's not sucking **** in from the atmosphere from some as-yet unknown location on the engine! The breather on top of the engine is the latest suspect as seems a little oily and loose. Just need to figure how to get it off?

Air duct grin grill into air box fitted right? You can hear turbo induction sounds if this isn't located on properly. Sounds great but it's warm air rather than outside air which is always worse.

Go round all your boost pipes, usual one to fail is under the sump and then over the front part of subframe, worn engine mounts put extra load on this and can cause it to come off or fail. Intercooler is super strong unlike newer cars.

Breather just pulls vertically off but it's a rare issue. Crank case smells get sucked towards turbo and burnt through induction again.