I initially thought my evap core was leaking due to the weird plastic smell from the vents that I recognized as refrigerant/oil when I first started the truck after it sat for a couple of days because I did not see any dirt or oil stains on anything under the hood. I've had to add refrigerant several times because the low side pressure was below 20psi on several occasions when checking it at idle with ambient temps in the high 80's. I was never able to get a leak detector to alert to the evap core and I did not notice any refrigerant oil stains on the passenger side frame and radius arm where the condensate drains. More and more, I started thinking the schrader valves in the ports were at fault.....I started seeing green oil around the low side port and the leak detector alerted to both ports.

Long story short, I bought a used recovery machine for $275 that looks like it had never been used, a new 30lb recovery tank for $75 and a used refrigerant scale for $50. After recovering 4oz of refrigerant, I pulled a vacuum down to what was very close to 28inHg on the gauge and it didn't visibly move after sitting for an hour with the pump off and valves closed. Weighed 29oz back into the system and it works better now than it ever has. No more refrigerant smell when I first start it either. I had the manifold gauges and vacuum pump, so $400 in tools, $40 in parts and I'm still ahead over $300 from the lowest estimate I got over the phone to do the same thing. Yes, I know about the Mastercool tools to change the Eaton valve cores under pressure....no one could get me one before July and I wasn't sure how much refrigerant was in the system so I wanted to know I was weighing in the proper amount.

 

So issue was low side port leaking?

 

Both the high and low side ports were leaking.

 

28" is not much it should be 29.5+ that could be the connection between the gauges and pump or gauge not calibrated not too big of a deal. No such thing as too much vacuum. I've seen too many so called pros do a 10-1`5 min vacuum though it's reading good and holding it's not enough time to remove all moisture. Put the pump on go have a long lunch. If you can do at least a single purge, triple is best. Draw a vacuum do a slight liquid charge, pump it down repeat. I don't know why HVAC still use sniffers especially since you need different sniffers for different gasses. I bought a quality ultrasonic 20 years ago and can find the smallest leaks from feet away behind panels even concrete in seconds. It doesn't care if freon, nitrogen, air or vacuum it finds leaks. Of course I paid for it 2K 20 years ago but it has paid for itself many times over. The 300-$500 don't work

 

Nice job! I know several mechanics (including myself) that just make it a habit to replace those valves whenever they do A/C work. They're pesky little buggers! What were your pressures after you'd filled it back up? Do you remember?

 

Thanks. It was in the mid-80's and from what I remember they were around 35/200 at idle with the windows open and fan almost on high after I weighed the 29oz in. I should have taken a photo but didn't because I was also working on this in the middle of other things and wanted to finish up after the hour and a half or so spent letting the vacuum pump run, watching the gauge to be sure there were no leaks then more vacuum pump time.

When I first started the truck after putting one 12-oz can in, I was worried because the low side was sitting up around 50 psi as I was adding the second can. Then the clutch fan engaged, I felt a blast of hot air and the pressure dropped to around 25 as I continued to fill it. Pretty cool to see the ECM command the fan on and watch the pressure drop so quickly with the increased air movement.