Hi all. looking for a little help diagnosing this problem. First of all this is on my 03 Expedition with the 5.4. There is a wierd buzzing noise that only happens when the A/C or heater is turned on and I rev the engine. I also noticed after checking it out reving the engine there was a greenish/black leak on the driveway. I'd hate to take it in and find out its something I could have fixed myself. Thanks in advance for any help with this.

 

Looking at it again this morning I discovered its only when the A/C and the defrost is on. No noise with just the heater on. Sounds like a fan spinning fast buzzing. So definitly somehing with the A/C. Anyone have any guesses?

 

Do you have the factory intake? My 07 F150 started making a buzzing kind of sound at certain times when the AC was on also I found out that it was the intake slightly rubbing the top of the fan shroud. Try holding the intake peice and see if the noice stops. I just recently put a K&N intake on so that seemed to be the problem for me.

 

AC system noise (especially when activated) can often be traced to the compressor clutch.....

However, you mentioned the defrost, too... which I assume you mean to be the heated window defrost option... which is a resistive load, much like a toaster

The window defrost and ac clutch can put strain on a weak alternator... and failing alternators have been known to 'buzz' before they fail.

 

I'm thinking compressor clutch, because when I said it happens when I turn the defrost on its when I push the button for floor heat and front defrost fan, but not when the regular defrost button is on. How hard is that to replace?

 

Westpoint- I suggest spending some of the best money you'll ever spend. You can buy a "mechanics stethoscope" at Harbor Freight for about $5. or so. I have 2 of 'em, and wouldn't be without one. Takes the guesswork out of where noises are coming from. You live in SC so you should be able to pick one up in OC without having to mail order it.