So I just picked up a used 03 MCS with 27k miles and in the last few days I've noticed that when the A/C is on or was just recently on there is a strange noise that sounds like some sort of pump... except a pump thats not working correctly. Does anyone know what this could be??? Its pretty loud from inside and outside the car. I'll see if I can get video clips of it, but I don't know if it will pick it up. Thanks

 

I bet its your power steering pump. That's my first guess. Hopefully I'm dead wrong and your PSP isn't.

 

I don't think it is because it only happens when the a/c is on or just recently was on.

 

Turning the A/C on overloads the cars temps. Which then puts more strain on your power steering pump fan which is directly linked to your power steering pump.

Like I said, I could be wrong. But it's worth examining. Get some videos up and then we can better assist you.

 

i just tried to do the video thing and you can't hear the difference over the rest of the engine noise on it... i'm gonna make an appt at MINI and let them check it over

 

I too think that it's your power steering pump, unfortunately. Last summer I had a loud vibration and noise that could be felt often when warm out, and I could trigger it on/off by turning on/off the air conditioning. However, when the A/C (and the rumbling) were on, I could make the noise change pitch by turning the steering wheel. That's the acid test for whether it's your steering pump or not - go out to the car, turn it on, turn on the A/C and wait for the noise to start up after a couple of seconds, and then slowly turn the steering wheel to one side about 45 degrees. If the rumbling noise changes, you are likely to have a steering pump issue.
My pump was replaced by MINI last year when I took the car in (under warranty) and showed them this simple test. I think the symptom is back this summer, so I'll have to go in at some point and complain about the rebuit replacement pump too.