AC making weird noise

[Georgia_Birdman]

When I first turn on my AC after my engine hasn't been running for a while, it makes a weird rumbling noise. It sounds like, "grrrunk grunk". It is two or three short bursts, then it doesn't do it anymore. It won't do it if I turn the AC off and back on. It only does it after the engine hasn't ran in a while. BTW, I did add refrigerant a couple of weeks ago. The pressure is around 45 psi. Any ideas?

 

[XLTrunner]

My guess is your bearing is on it's way out.

 

[Georgia_Birdman]

Doesn't sound like a bearing. I am wondering if I overcharged the system.

 

[koda2000]

Around 30 PSI on the low side sounds more normal to me. It might be overcharged.

 

[Georgia_Birdman]

Also, there is a small port behind the compressor. When I turned on the AC yesterday morning, a small puff of mist came out of this hole at the same time the noise was going on. BTW, what is that hole for?

 

[BKennedy]

I think that is the pressure relief valve, so maybe you have too much pressure in the system.

 

[koda2000]

I'm not aware that Ford ever put a relief valve on the A/C system (I could be wrong). Could that be the lower part of the high pressure switch? That's where the high pressure switch is located on my 01 Sport Trac. I know because the previous owner broke the top off the switch while changing the #4 spark plug. I was able to find the top to the switch shoved in a hole on the frame and I glued it back on. Mine didn't even work without the top on the switch. Maybe your's is jumped?

I'd drop the low side pressure to around 30-32 PSI and see if that stops your noise.

 

[974X4BLACKSPORT]

Put gauges on the a/c and check the high and low side.

 

[BKennedy]

I know my 1994 has a pressure relief valve. It blew when I was over 9,000 feet up in the Sierra's after some AC work was done a few weeks prior. I thought something in the cooling system blew, but when I went to look, that brass thingy was covered with green AC oil. It still ran cool after that so I figured it was over-pressured due to the recent service and altitude.

 

[donalds]

Pressure release valve I had to replace this on my 99 cheep fix
Sounds like overcharge of the system
Mine rides at about 28 when the compressor is on
Also the a.c. clutch will sound funny when you let it sit it gets a little bit of surface rust on the clutch material that will rub off when it cycles a few times

 

[Georgia_Birdman]

It is around 35 psi with an outside temperature of 75 degrees. I may need to have the system evacuated and recharged. I am going to take it to my mechanic next week. I just wanted to get a few opinions. Thanks for all your help.

 

[Georgia_Birdman]

According to my mechanic, I didn't dodge a bullet, I dodged a missile. I seriously overcharged the system. According to the vehicle specs, the system is only supposed to be charged to 1 lb, 14 oz. I had 4 lbs in it. Luckily the relief valve saved me and nothing was damaged. He evacuated and recharged the system. Everything is good now. I just made a stupid mistake which was almost a costly one. His advice and now mine is don't trust those cheap guages on the recharge kits. Let someone who knows what they are doing maintain your account system. I will admit that I am not qualified for this.