I can hear a strange humming sound when I fire up my x305.
It lasts about a 30 seconds, perhaps a minute, then stops. It always stops before I can figure out what it is.
Any thoughts?
Its pitch changes with engine revs.
Any help much appreciated, as it will help me narrow it down.
I’m guessing it must be something that’s driven by the engine, but has some kind of clutch mechanism that disconnects it.

 

Secondary air pump.

 

If it is the secondary air pump (I assume I’ll be able to tell now I know where to look), any thoughts on the urgency of replacement?

 

The pump might be home-overhaulable.
https://www.jaguarforums.com/forum/x...e-done-246347/

 

My car has the start up hum from the air pump also, and it’s nothing to be concerned about. You can only hear it because everything else is so damn quiet.

 

As I wrote in the thread above, if you are concerned about excess noise from your smog pump you may just need to detach the in and out air hoses (accessible from the wheel arch) and putting some compressed air through it to clear out any dirt and dust that has been ingested.

Also blow some air into the clutch gap area at front of pump as crud can get in there and cause slippage/noise.

I never reasssembled the smog pump I dissected, must get around that.

 

There is a specific secondary air pump relay on the V - 12 you can pull

There is a fuse , but is shared with the injectors so no run

Pulling the relay will not effect other things except smog test

The relay can be stuck in the socket and can be freed up with some penitrating spray of the water seal square seal in the seam after you flip it upside down

The relay may be pitted on the power contact inside comprising the proper power to perform and can be swapped with a same part # headlight , fog , A / C clutch of the same LNA6707 abouts

You can see how easily the relay's mounting position can be swapped around by error

Oliver Marks has opened his V - 12 smop pump for complete overhaul and is a different pump than the inline 6 I took fully apart to repair

Would a soaking with penitrating oil for a while help ?

 

You don't get a CEL? I was reading the OBD-II manual and theres a bunch of possible codes for inop air pump, which scared me into not disabling mine.

 

You will get a CEL without a smog pump. The thread I linked to was about how to keep the smog pump operating efficiently. The one I took apart was a spare, not the one on the car.

 

Original poster N Bath has a smog pump that is turning somewhat just noisy so may not show a code in my opinion ( not a V - 12 owner )

 

G'day Gents,

My car, a V12 built for the British market, has no smog pump and no associated CEL so there must be a way to program the BPM or ECU to allow for this.

All that is there in the pump's place is an idler pully.

Cheers,
Jeff.