"Sawing idle sound" when AC is on

[mitch2k]

Hey folks,

When I put my airco on, or the big lights, and the engine is idling, it makes kinda of an "sawing" sound. The rpm goes a bit up and down.
The garage that refilled my airco says this is probally the managment of the dieselpump.
When you look in BMW TIS, it tells to replace the dieselpump.

Is this something to worry about? Cause I dont feel like spending $2500 for replacing the pump...

Thanks for the input!

[joshua43214]

where in the enigne is the noise coming from?

[liquidtiger720]

When I had this problem...it was become somebody backed into the grill and pushed the metal supports in front of the fan causing contact.

[mitch2k]

It is from 'the whole engine'. It is not one part that is making the noise. It is like somebody is pushing a bit up and down on the pedal...The RPM jumps up and down..

[joshua43214]

Take a piece of vacuum hose or other small tube. stick one end in your ear, presto, you have a directional mic. wave it around the engine bay and try to pin down an area or part.

[632 Regal]

if the sound goes away above idle your belt could be loose/glazed/need replacing.