Hi All
I noticed a noise coming from the front RH corner area today with the engine ticking over {2005 X350 3 ltr}. Roughly the same area as the suspension compressor but the other side. The last time I had the plastic liner out I noticed some sort of unit at the front, above the bumper and made a mental note to find out what it was. Overtaken by events I put the liner back and promptly forgot about it. Does anyone know what lives under the front right hand wheelarch cover above the bumper and would it make a noise like a motor running?
Any information most welcome.
Thanks
Pete

 

The module under the RH bumper cover is the Secondary Air Injection Pump. I thought those were only fitted to North American vehicles, but obviously you have it on yours. It's more-or-less a vacuum cleaner motor that will blow air into the exhaust manifolds on cold starts to warm up the cats faster. Should only run for 30-60 seconds on cold startup. Sounds like your motor just wore out.

 

Thanks for that information mhamilton. I'll see if I can disconnect it.

 

The other thing in that position is the headlamp and windscreen washer tank and pump(s)

 

I have the same noise. Happens at low speed and is not engine related. My mechanic thinks it could be the air pump mounts. It can be very annoying, sounds like a can of marbles to me

 

Curiosity got the better of me yesterday and I took the right side front wheelarch liner out to see the offending item. It's a black barrel shaped thing about 6 inches in dia and about 6 inches long but dimensions are just a guess from fading memory. I started the car up from cold and the contraption started up. After about a minute and a half the tone changed as the control valve which allows air into the exhaust system closed then after a few more seconds the pump stopped. I think that's exactly what it's supposed to do but only after a cold start. Apparently it's to help burn off unburnt fuel particles and raise the temperature quickly to reduce emissions and protect the cats. I'm sure mine was running continuously the other day but of course it's behaving itself now. I noticed that there is a hole in the front apron right underneath the pump so you can see it if you look up and even touch it with your finger to see if it is running.
My last X350 was a 2004 and didn't have this system so I'm wondering if it ever goes wrong I could somehow disable it. Fuse No27 in the fusebox on that side seems to be the protection for the system and if it ever starts running again when it shouldn't I'll pull the fuse and see what happens.. The relay for the pump lives right next to the pump so maybe that's a suspect if it runs when it shouldn't.
Good luck finding the marbles.

 

From what you describe this is indeed the Secondary Air Pump. This is what it looks like (photo from an eBay auction):


Unfortunately pulling the plug/fuse/relay will cause the ECM to set some codes. It monitors the AIR system on startup to see that it is performing correctly and that the valves are opening at the appropriates times. If your pump was running continuously past approx 30 seconds on a cold start, then I would also suspect a stuck relay. These pumps are not meant to operate continuously.