I do have a vacuum pump that was going to be my next step. I got lucky a few years ago and picked the pump up at a second hand store for around $25 if memory serves. I doubt it's been used more than a few times.

I just got back from a store run so I'll look in a bit to see if there are any fresh signs of the dye and hook the pump up. Like you say - not much to lose at this point so might as well try that next.

Curious there's green around the clutch though. Hard to say where it came from if it's not a leak.

 

I'll pipe in that I'm sort of with the "if it's not broke don't fix it" on this one, but sounds like you do have a leak.
a few years ago shortly after I got my current 04 lariat I noticed that it lost pressure within a few weeks to the point the ac didn't work at all. After some investigation I found that the leak was between the two halves of the compressor housing itself. So I replaced it with a denso brand compressor and replaced the orifice valve filter thing and that's all. Vacuumed it down for a half hour and then let it sit for another hour to watch the gauge, and it's still good 3 years later.

If you see green dripping from the clutch it's entirely possible you have a leak from the compressor.. take a close look at that. It may help to clean the area with brake clean so you have a fresh start.
Another thing to consider is if you can't find the leak, if the system is already empty you can pump it up with compressed air to 100 psi and squirt soapy water on all the connections and the condenser and look for bubbles.

Lots of people say you should replace the receiver dryer/ accumulator but unless you have a compressor that grenades and leaves the black death inside the system it's not totally necessary, pulling a sufficient vacuum should boil out any moisture.
replacing the orifice is a no brainier though and gives you an idea of the health of your system based on how clean it is. I think it's in the upper tube you unhook at the condenser that runs past the passenger valve cover.
Last thing is I have rented gauges several times from O'Reilly's but I have seen hit or miss with leaky gauges so finally bought my own set, because of your gauges leak you will end up chasing your tail looking for leaks in the system that may not be there.

 

I have the vacuum pump on it now while I'm off on other 'honey-do's' around the house. It's been running for about an hour.

The vacuum is sitting at about -27, -28 at the moment. I can't get more accurate because the gauges aren't graduated very well. I don't think I'll get any better vacuum considering my altitude (approx. 4100ft ASL). When I did my smaller truck I couldn't figure out for the life of me why I couldn't pull any more vacuum until I read about factoring in your altitude. I think 27 at my altitude is the equivalent (more or less) than a perfect -31 at sea level... or something like that.

I'll shut the pump off shortly and see what kind of hand I've been dealt.

PS: I did a quick look at pump and dryer prices. For OEM parts, I'm looking at about $70 for the dryer and $225 for the pump. I don't think that's too terrible? Unless there's another brand I should look at. I did see the Denso pump but I wanted to do more research on reviews. A few people's reviews (Amazon I think) wasn't too happy with their warranty related issues. Amazon came through but apparently Denso wasn't helpful. But it was only a few out of many other happy customers. And we don't really know what happened or the person's skill level, etc.

And if I do have to replace the pump - what do you guys do to flush the system? I should at least try to clean it. I noticed there's a kit you can buy that forces the cleaner through using your air compressor. Sorta spendy though for something I may not ever use again (around $40 - $60 after buying the tooling and bottle of cleaner). I'm hoping there's another way?

 

I've replaced two or three vehicle compressors and just vacuumed them about thirty minutes before adding R134a. I figured that since I saw no evidence of metal shavings or other debris there was no need to clean it. Just my experience though.

 

Same here.. If there's not gunk in the system it's probably not worth trying to flush it. The orifice tube should give you a good idea.

 

• Any luck finding the leak?

• My years-ago experience with Denso is that they make quality parts. And Needsmoarturbo has been using a Denso compressor for three years.

• Good idea

• Thanks Needsmoarturbo. I've wondered about using compressed air before but wasn't sure it would work and didn't take the time to learn how. And I just went and checked my gauge set and the yellow hose has a Shrader valve fitting that can be used. So, I'll definitely use this method to find leaks in the future. The UV dye method has always puzzled me sense sucking instead of blowing to find a leak didn't make sense.

 

UPDATE:

It held a vacuum overnight so... I can assume no leak. Not sure why or how it has a yellow dusting around the front of the compressor though.

I did notice that when you remove the caps from the charge ports, they gave a slight pressure release and then immediately stopped. Is this normal or am I looking at the Schraders going bad? It's the only weak point I can currently come up with.

I have seals inside those caps but not sure if they can hold pressure very long. I'm wondering if that's where the leak came from. I do want to replace them eventually. I would have already done it but my local shops don't have that gigantic Ford one for the High port. The universal kits didn't help either. Another Ford-only thing? I don't know. The caps in those universal kits didn't fit either.

I went ahead and re-charged the system. I figure nothing to lose at this point except the cost of 3 cans of Freon. If anything it will tell me if the system still works or if I have a major leak that I just can't readily find.

It took 3 cans and now the pump is staying on like it should and the duct temps is sitting at a nice 52 degrees (72 ambient). I'm no pro, but I think that's a success? Time will tell if the Freon doesn't escape again.

Question: I read that vacuuming the system will generally NOT remove the oil that's already in the system - or if it did, not enough to worry about. Of course I didn't notice any being pulled out. The system was pretty much bone dry of Freon when I started this adventure.

Should I add any oil back for safe measure? Can a person put in too much oil?

Thanks again everyone! You've been a huge help!

Now back to Honey-do's !

 

I suppose it's possible to have a leak under pressure, but not under vacuum I guess you will find out now.

I think I wouldn't bother adding oil unless you have to replace components line the compressor or condenser.

 

I was wondering that too. Sorta like having a micro-fracture in a cylinder. It won't leak until the engine is heated up and expands the crack. Boy oh boy I've chased my tail on that one more than once on a friend's Dodge engine. We couldn't figure it out for the longest time until we tore it down and broke out the Magnaflux. Whoever invented that is nothing short of a genius! That was eons ago. I'm not even sure if shops still do Magnaflux or is there some new kind of Star Trek Tricorder that can do it.. lol.

So I'll see what happens. I think replacing those service Shraders won't hurt. I see there is a tool to do it without discharging the system but it's another one of those 'use once and toss it in the toolbox' things. I might see how much an AC shop can do them for. How much could it possibly be and to have it done right. Or just wait and see. I should know fairly quickly if it's going to leak out again.

I did try and get that high port valve loose to measure it and it's not budging, but then again I just have one of those crappy pencil-like tools that you can't get a grip on, so I'm a little worried about trying to change it. Maybe a few drops of PAG oil might help loosen it before I attempt it again. I read some people used Liquid Wrench in there but I don't know if that's a good idea introducing oil like that in the system. Probably not enough to worry about, but what do I know.

 

Glad to hear it held pressure overnight, and that you got it blowing cold again.

I've had a leaking Shrader valve, but it wouldn't hold the vacuum. Just immediately began slowly leaking. To test for a leaking Shrader valve you can brush some soapy water on it.

I've never added back oil back except for replacing a component (compressor, condenser or receiver/dryer) when vacuuming system. And, I think I would have heard to do this from others online if it was necessary.