BMW X5 4.8is Strange Rattle Noise from Underside...

[Lion Heart]

Hi guys!

I recently got a 4.8is and noted it had a rattle noise from the engine area. I'm pretty sure it's not cam chain related as that would (I beleive!) normally manifest itself upon cold start up due to the oil pressure being initially low. I also thought maybe vanos, but by further investigation is seems the rattle is louder from under the car...

So recently I did an oil and filter change and everything good.

However, the rattle noise is still present. It does not happen on cold start up, but generally after 30-60 seconds or so.

However, I had the car on a ramp and so could have a good look and listen around. The rattle is actually FAR more noticeable (twice as loud) from underneath the engine...

The noise seemed to be eminating from the sub frame plate area, through the hole where the oil filter cap is, and at the back of that plate where the engine meets the gearbox. That said, this could be because those are the two areas where it does not have the plate and so bound to be louder there (i.e. the plate will help block the noise).

But DEFINITELY 100% a lot louder from underneath the engine.

Does anyone have any idea's on this???

[henrym3]

Might I suggest you get a long screwdriver or similar and put it to your ear and touch the end of various different bits on the car/engine, this will highlight the noise and localise the area, first place to try is the cats, could well be broken inside and start rattling once heated and have expanded.

[Lion Heart]

Hi henrym3

Yes, I'm liking that idea. I'll give that a try!

I'll be back with the results, and any other ideas most welcome in the meantime!!

[allanhelen]

Just had a similar noise on my E70 4.8i and it turned out to be the water pump

[IanP]

Maybe cat internals coming loose?

[X5Sport]

Could be a torque converter going bad?

Any sign of trouble (hesitant, slower, reverse not engaging instantly) with gear changes?

[Lion Heart]

I put a screwdriver to my ear on the cats, and they sounded absolutely fine so not those.

As for the torque converter, no issues at all driving. Gear changes etc all good.

As for the water pump, was your rattle noise appearing to come from the location I mentioned, and where is the water pump located on these, anyone know?

[allanhelen]

Water pump is located at the front and is belt driven.

Mine had the rattle from cold, you could clearly hear it in the cabin and lifting the bonnet it seemed to come from pretty much everywhere. I never got under the car so can't tell you what it sounded like from there. Initially the noise did calm down once the car warmed up but as it went on it just rattled all the time. 

[Lion Heart]

Thank you for that. Yes, I thought it would be located on the front. The noise does not seem to be coming from the front of the engine, but the rear (bottom).

[IanP]

Flwheel to torque convertor bolts? Its only a thin steel affair

[Lion Heart]

Interesting... Are those accessible from he outside (i.e. without removing gearbox) at all?

[IanP]

Some engine have an access plate, not sure on yours though