Loud "farting" sound when accelerating

[Brianibew]

Your a/c compressor is shot. My 2003 silvy did the same thing. It would only make the sound when accelerating past a certain rpm. The plastic reed valve in the compressor broke and the compressor is destroying itself inside. Cut/remove the ac belt and the noise will go away.

[Jsdirt]

That's a good thought, but only if he has the A/C on when accelerating, and the compressor is engaged. If the A/C isn't on, the compressor isn't turning.

[Soules75]

I have been running the AC a lot lately due to warm weather. I've had issues with my AC in the past. Was going through AC belts and ended up replacing the AC belt tensioner which was all locked up. Also used a more expensive gator belt and hadn't had problems since. But I haven't been able to replicate the noise with the AC turned off, and since I saw no signs at all of scratches or anything on the fan blades or shroud, I lean toward an issue related to AC.

 

I can't stand being hot, so there's no way in hell I will just live without AC. How difficult is it to replace the AC compressor? Is it expensive to have a mechanic do it?

[Jsdirt]

Replacement is pretty straightforward. Some things I do before installing is dump whatever oil is in there out, then flush the compressor with whatever oil the system takes (filling and turning the compressor by hand or wrench 10 times or so in each direction, dumping, & repeating), then refilling with the amount you removed from the old compressor. I use Nylog on all o-rings. Stuff is like liquid snot - super sticky gummy stuff that will seal anything from leaks.

 

I'd also replace the orifice tube and accumulator as a matter of practice. The accumulator has a desiccant bag which absorbs moisture from the system. Good to change whenever the system is opened, although I've run systems in the past with decades old accumulators without a problem. I wouldn't do that with anything built in the late 90's or later though.

 

Without a vacuum pump and gauges you can't recharge properly - you MUST pull a vacuum on the system for a minimum of 30 minutes to get any moisture out before recharging. I leave my pump on and go do other things - sometimes for 3 hours or more. Can't hurt going longer. You can charge with those cheap crappy store-bought single gauge deals, but I like to see what the high side is doing. Having both gauges is much better.

 

If you do it right, you'll do it once.

[Brianibew]

The sound your hearing is the ac belt hitting your transmission cooling lines when the compressor is locking up. It will break those lines if you continue to drive it with the ac on.

[Doug_Scott]

You should be able to pull the wire off of the compressor that provides power to the clutch. That way the compressor cannot possibly engage by accident or being forgetful. Noise should be easy to diagnose with two people, one inside the truck with the parking brake applied, and one foot pressing hard on brake pedal, start engine, turn a/c on, put in drive, and floor the gas pedal. The brakes being applied should prevent the truck from moving, and the load on the engine will show a bad motor mount pretty quickly. If it does not make the motor rise up, look around the a/c compressor belt to see if it is slapping against something.

[Soules75]

Today I drove home from work (30 min drive) with the AC off. No noise whatsoever. Pretty sure it is AC related at this point. Probably need a new AC compressor then...

[Brianibew]

If only ac wasn't that important...its 101 in the Midwest today. At least it's nothing truly serious and easily remedied. Good luck.

[Jo-Jo]

I have the same issue! It's your ac pulley and belt. Im not sure if there is more to it or not. I've noticed with ac on, as I approach 2,000 rpm, the sound is made. It also has a hesitating effect. What's happening is your ac belt is forcing the pulley and over extending it. Man, I've been trying to figure it out for weeks and nothing. I replaced the ac belt and bought a new ac Delco pulley only to end up with the same results. Since your initial post, have you progressed?

[Brianibew]

I have the same issue! It's your ac pulley and belt. Im not sure if there is more to it or not. I've noticed with ac on, as I approach 2,000 rpm, the sound is made. It also has a hesitating effect. What's happening is your ac belt is forcing the pulley and over extending it. Man, I've been trying to figure it out for weeks and nothing. I replaced the ac belt and bought a new ac Delco pulley only to end up with the same results. Since your initial post, have you progressed?

Jojo, the answer to your problem is in the posts above. Your AC compressor is shot, no doubt in my mind since this exact issue happened to me. Make sure your system gets flushed to remove all the metal that your compressor just injected into the system, otherwise your next compressor may have a short life. The problem is not the AC belt or idler pulley, it's the compressor.

[Jsdirt]

Interesting failure.

 

Just last year I changed the 29 year old OEM compressor in our '86 Grand Marquis. Was still working, but noisily. Original pulley bearings too - 220k + miles on it.

 

If only automakers still built things to last ...

[Jo-Jo]

Your a/c compressor is shot. My 2003 silvy did the same thing. It would only make the sound when accelerating past a certain rpm. The plastic reed valve in the compressor broke and the compressor is destroying itself inside. Cut/remove the ac belt and the noise will go away.

Thanks for your response in regards to my post. I wanted to avoid replacing the compressor, but if its what I have to do then so be it. Now, on your post you mentioned "cut/remove ac belt and the noise will go away". Did you mean to say remove the compressor? If you did actually mean the belt, how is that a solution if the compressor is destroying from within? Thanks again.

[Jsdirt]

All you have to do is unplug the clutch coil wire to the compressor, just to avoid accidental engagement (someone turning the A/C on without you knowing). Belt will be fine - the compressor is just an idler pulley when not engaged.

 

If it's easier to reach, you can unplug the LPCO switch on the side of the accumulator. That will do the same thing (prevent power from reaching clutch coil).

 

Hopefully it didn't scatter itself through the whole system - that gets expensive ...