A/C schrader vavle replacement

[Mountain Gnome]

The schrader valve on my A/C compressor is visibly leaking oil. When you unscrew the cap, a bit of pressure is released.


I got a type of tool that I randomly saw on a youtube video that allows you to replace the valve core without discharging the system.


1) Put quick-connect tool on valve.
2) slide valve-core "socket" on a long bar down through tool

3) engage with valve-core,

4) twist counter-clockwise to unscrew the core,

5) pull long bar back up through tool
6) close ball-valve in tool
7) unscrew "long bar" assembly
valve core should be there at "socket" end of bar, or in tool above ball-valve.
9) reverse with new core to re-install


Yet the valve core is not there....
plenty of pressure built up in the tool....immediately
I can spin the socket/long-bar part, feel it seem to engage with the core, and after a bit of rotating, I feel something that seems like "threads" that have reached max....it pushes out as I spin until one point, then drops back in, and starts pushing back out again until that same point in rotation and it drops in again.


Looking in the valve before I started, I saw that the hole that the core sits in is a 2-step bore, both steps threaded. The bigger diameter bore, closest to the hole opening, is threaded for the cap, while the core sits deeper in the smaller bore.


I'm wondering if my core is free of its smaller bore, but is cocked a bit sideways in the larger one (with bigger threads, I think), and that is the feeling I'm feeling.


Seems like if I can't finagle it to come out, but it is unscrewed even a little, I can't take the tool off. Can't re-install the compressor or therefore drive the bus.


Do I have to buy a vacuum pump and suck out the system through the low-pressure valve?


The youtube video made it seem like spreading warm butter on hot toast.


In my pic, the main tool body is on the valve, and the socket on a long-bar is on the wooden block on the ground


I'm gonna try some more (wearing a welding helmet so I don't blast myself in that small space hunched over under the bus), but if anyone has a comment or suggestion, fire it up!

[Mountain Gnome]

OK that was fast.


I tried screwing it back in, and I hit the bottom and it stopped turning, so I knew I was connecting the tool socket with the core.



I tried to "unscrew" it a few more times, but then it hit me:


I turned the A/C compressor unit upside down (fighting against the rubber hoses), and unscrewed the core that way. At first it got stuck in the ball-valve, so I knew it was loose! Then I just tapped on the tool with the little mirror I had, and the ball-valve would close, so I knew it came out like it should. And it did.


I flipped it back right-side-up to install the new valve.


Did the same with the other side (low pressure side) and no problems. Done in under 5 minutes. Well worth the less than $30 I paid for the toolset, and it does my R134a and R1234yf. Could have paid near $300 at a shop to evac it, replace the core, and refill...


One thing I noticed:
The old cores had black rubber o-ring seals (and the one on the high-pressure side that was leaking oil looked old and worn), while the new ones that I bought at Advance Auto Parts and the ones that came with the toolset (bonus!) both had clear rubber. The black ones look like tire valve cores. I wonder if someone.........like the guys who installed the wrong alternator to use with a battery isolator (or visa-versa) or if the dealer (in Tucson) who sold the bus to the school did the work....I had them check my air-brakes on day one because they didn't feel right to me (but I had no air-brake experience before, except maybe test driving another bus) and they said all's OK, and three days later, my treadle valve went out on the highway. A new valve and it worked like it should, and a dealer should have known that was a problem by my complaints and a test drive 10 feet. They mentioned that the school system my bus came from "takes care of their buses' maintenance", so I might assume they were doing the work if they know about the work.


Anyway, I could hear pressure release when I took the caps off the A/C system valves after only being on for a few minutes. First test with the new cores and no hiss of pressure! I'm going to leave it there overnight and see what happens when I remove the caps tomorrow, hopefully no hiss, and then remount the compressor on the engine.


Peace y'all. Aloha!

[Rwnielsen]

Good job. That would intimidate me something awful.

[cadillackid]

sweet!!!! I love those tools!! so much easier than recovering and recharging the air conditioner system!! its a must for anyone working on their A/C. the schraeders are as major source of leaks. and the O rings i nthe caps esp the discharge rarely stop all leakage..

[Mountain Gnome]

Originally Posted by cadillackid

the schraeders are as major source of leaks. and the O rings i nthe caps esp the discharge rarely stop all leakage..

Yea, I heard that they were a major source of leaks, and intended to replace them all when I had the system discharged last summer to replace all the hoses.


Then I forgot to replace the valve cores like a D.A.


Never saw O-rings in the caps...looked for them.


The new "A/C service kit" I got from Advance had new caps that I did not use. I should look to see if they have O-rings installed!


The tool kit came with 2 new R134a cores, 2 new R1234yf cores, and 2 sets of 2 different sizes of O-rings. I was thinking the O-rings were for the R1234yf systems, or for the tool itself (there is a small O-ring on the "socket-stem" that seems the same size as one of the extras). Maybe the bigger O-rings are for the caps?


I think the thing that was giving me problems is the fact that this tool is for both systems, and the R1234yf core is slightly larger diameter. This means the bore-hole in the tool itself is slightly larger than the R134a core that I was removing, so the pressure just "goes around it". That pressure pushes the "socket-stem" back up/out. If the tool was made just for R134a, the bore in the tool would match, and the pressure could push the core back up/out also, and I would not have to turn the thing upside down. That is what I saw in the video on youtube.


I had my compressor unmounted for other reasons. If you had to unmount the compressor (in a car or something) that would possibly be more work than just a discharge, and it may not be possible then to even turn it upside down if the hoses are too short or not flexible enough.


Worked great for my bus, though.

[Mountain Gnome]

I forgot, I was thinking that maybe a bit of something sticky on the end of the "socket-stem" would pull the valve-core back up and out.

[cadillackid]

My tools are separate . It’s older so it’s 134a only, and one for the SAE 1/4 HVAC . I don’t own the 1234yf fittings or tools . Both cars with it are under warranty

I’ve seen caps with and without O rings at the parts stores.I usually try and get ones with Just for that extra layer.

Sometimes just releasing a little pressure through the Schraeder seals it if there’s a wee piece of dirt stuck..

The charge ports on busses are all over the place. On cars they are usually in line on top so you don’t have to pull the compressor. (although old foreign cars had them on the bottom ).

Busses are wherever they seemed to feel like putting them.

I try to make them accessible as I experiment with enough different refrigerant blends and charge levels that I always want to access them .