I had to laugh when I searched old threads for "grinding", "growling", etc. All kinds of posts came up! I guess XJs really do make a lot of noises. But I really couldn't find anything that sounds like this;

I have a '99 XJ that I love dearly. I just got the A/C charged, and now sometimes when I turn it on, it makes this weird growling/grinding/low-pitched-like-I've-never-heard-in-my-life noise. It sounds like it's coming from the right hand side, down low in the engine. I sometimes also get a little squeal from the belt, but it stops as soon as it runs for a few seconds.

I imagine that the compressor is going out. Figures. But what is that grinding noise?

 

Could be the clutch on the compressor. Or the compressor itself, I suppose.

Check the auxilary fan though, even though it's on the opposite side. Mine was cracked and made a ton of noise / vibration when it ran. Swapped it for a better one and now my AC is nice and quiet.

 

That sounds right. It does sound like gears that are slipping. I will have to figure out how to look at that. Thank you!

 

Oh, and I forgot to mention that it only does it for about 2 seconds and then quits after the compressor starts running. And hopefully no one is around when it happens because it's really loud and almost sounds like a large electrical buzzing like a "zzzzzz". I just cannot describe the sound. I had my husband listen to it, and he said he's never heard anything like it before either, and he used to work on cars!

 

The compressor cylinders are full of oil when it first engages, once the extra oil pumps out the noise goes away.