Troubleshooting AC leak before charging with R134a

[1991 Corvette ZR-1]

I have recently done an overhaul of items in the AC system and I am running into a leak when vacuum testing the system. So for the things I have done:

Rebuilt the compressor
New Condenser
New Accumulator/Dryer
New compressor hoses
New orifice tube
New pressure switches
All new o rings coated with Nylog Blue sealant

The compressor was filled with a little over four ounces of oil containing UV dye. The rest of the UV dye oil was put into the accumulator. Strangely, I pulled vacuum on the system for over an hour and 20 minutes and it maintained -30 in Hg on the low side and high side. It was not until I did a subsequent test due to paranoia that I can no longer duplicate the required hour of vacuum being maintained. The high side appears to hold vacuum while the low side is losing half of the vacuum in about 40 minutes in the attached picture. I have double checked the fittings to make sure they are not leaking but part of me thinks that is the case.

What all is isolated to the high side? What is considered low side focused parts? Part of me wants to charge the system and look for the potential leak with a UV light after a few drives. BUT the idea of a slow leak of R134a refrigerant in the garage does not sit well with me either.

Wanted to make sure I tried everything before giving in and having a shop leak troubleshoot. I would not think a leak decides not to leak one test then decides to the second time I test.

[XfireZ51]

Following this. I just installed a ?newer? condenser. In my vacuum testing, I am able to pull -29? vacuum but lose it all within an hour or so. I didn?t realize you could test high and low sides individually.

[1991 Corvette ZR-1]

Following this. I just installed a ?newer? condenser. In my vacuum testing, I am able to pull -29? vacuum but lose it all within an hour or so. I didn?t realize you could test high and low sides individually.

I pulled the new compressor hoses off the compressor and in the process of vacuum testing the system closed off now minus the compressor. There is a schrader valve on the compressor that will allow me to pull a vacuum on the compressor all by itself. So we will see if that unit can hold a vacuum as well. The condenser sat on the shelf for months until I removed the plastic fittings and was greeted with a loud pop and hiss so it was vacuum sealed and held it this entire time, I am going to rule that part out.

Knowing my luck, it will probably be the evaporator. Only way I can think of to check the system if these other parts check out separately, is charge the system and run it then look for leak with a UV light. Maybe pull the fan motor and peak in with the light to see if any leaks are showing on the evaporator.

I would strongly consider a custom eliminator pulley at this point! Pull it all off and lose some weight in the process.

[1991 Corvette ZR-1]

The compressor I rebuilt checks out. It maintained -30 inHg for three hours. Next step is undo the low pressure line from the top of the evaporator and the high side from the bottom portion of it. I will plug those ends as well as the ends of the new compressor hose and pull vacuum off the accumulator. If that maintains vacuum for an hour or more, I will probably have the answer I did not want that it is my 30+ year old evaporator that is leaking.

For the compressor, I just removed a few bits so I could thread an R134a adapter onto it to clip a connection to. I guess I should have more faith in my rebuild skills. The hose port closest to the fitting pulls the bulk of the vacuum. With just that plugged, the gauge pegs at -30 inHg but the moment you close off the valves, the needle slowly heads to 0. With both ports blocked, it holds no problem.

Small victories, I guess.

[1991 Corvette ZR-1]

Compressor, hoses, accumulator and condenser all hold vacuum. The high pressure hard line with switches on it to condenser is suspect. I isolated the hard line by capping off both ends and attached high vacuum connection to it. Cannot hold vacuum with over half gone in 40 minutes or so. I do remember the black plastic sleeve on the part nearest to the condenser needing to be cleaned due to repeat oil residue over course of a few weeks. However, the fitting was leaking previously and I figured it was just running down from the fitting to the black sleeve. Guessing the line is rotted or compromised beneath that hard sleeve.


So where would one find a good reproduction of this hard line? The L98 high side line and the LT5 line APPEAR to be the same. Still need to test the factory evaporator still in place.

[1991 Corvette ZR-1]

Old condenser and low pressure line attached to it check out, Im surprised. I isolated the hard line which would not hold vacuum, so I pressurized it and found the high side schrader valve is leaking. Ordered valve stem removal and installation tool along with valve stems.


https://www.amazon.com/gp/aw/d/B07HC9FNQY/ref=ya_aw_od_pi?ie=UTF8&psc=1


https://www.amazon.com/gp/aw/d/B0023TQEFQ/ref=ya_aw_od_pi?ie=UTF8&psc=1

Was not exactly sure of the type of valve stem so I guess we will see.

[XfireZ51]

Old condenser and low pressure line attached to it check out, Im surprised. I isolated the hard line which would not hold vacuum, so I pressurized it and found the high side schrader valve is leaking. Ordered valve stem removal and installation tool along with valve stems.


https://www.amazon.com/gp/aw/d/B07HC9FNQY/ref=ya_aw_od_pi?ie=UTF8&psc=1


https://www.amazon.com/gp/aw/d/B0023TQEFQ/ref=ya_aw_od_pi?ie=UTF8&psc=1

Was not exactly sure of the type of valve stem so I guess we will see.

This is exactly what Marc Haibeck has said is the primary issue in AC leaks. The high side Schrader valve. He suggests putting a metal cap over it rather than plastic.

[Jagdpanzer]

Dorman has a brass cap for this purpose.
https://www.dormanproducts.com/p-80262-902-025.aspx


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[XfireZ51]

Dorman has a brass cap for this purpose.
https://www.dormanproducts.com/p-80262-902-025.aspx


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Phil,

Assuming this works for our system after converting to R134a, correct?

[Jagdpanzer]

Far as I know they only work with GM style R134 service port fittings with internal threads. My 94 ZR-1 has this type from the factory. Earlier cars which were originally with R12 have the old styleR12 service port fittings.


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[1991 Corvette ZR-1]

Dorman has a brass cap for this purpose.
https://www.dormanproducts.com/p-80262-902-025.aspx


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Thank you for this. I ordered it and should have same day as the schrader valve removal / installation tools. I will coat the threads with some type of sealant, thread it in the R134a adapter and do another vacuum check once I have it.

[XfireZ51]

Thank you for this. I ordered it and should have same day as the schrader valve removal / installation tools. I will coat the threads with some type of sealant, thread it in the R134a adapter and do another vacuum check once I have it.

That was going to be my question regarding the 134a adapter. What sealer are u using for the adapter to the high side port?

[1991 Corvette ZR-1]

That was going to be my question regarding the 134a adapter. What sealer are u using for the adapter to the high side port?

I will be using Nylog Blue gasket and thread sealant. It is formulated to work with AC systems and will not contaminate the system. I used it on the new O rings I installed throughout the system.

[ghlkal]

Good, informative thread.

Thanks for documenting your work 1991. :thumbsup:

I too had a leak via the high side schrader valve, and it took several different valve stems before it was fixed. (Hopefully it's still holding this year ...)

[XfireZ51]

I?m picking up the Dorman Zbrass fitting tomorrow from AZ.
Is it possible to check if system holds vacuum without connecting to high side valve fitting?

[1991 Corvette ZR-1]

Good, informative thread.

Thanks for documenting your work 1991. :thumbsup:

I too had a leak via the high side schrader valve, and it took several different valve stems before it was fixed. (Hopefully it's still holding this year ...)


Thanks! Hopefully it helps someone else out.


I?m picking up the Dorman Zbrass fitting tomorrow from AZ.
Is it possible to check if system holds vacuum without connecting to high side valve fitting?

I?m not an expert but the system as a whole is circular, so I will say yes. As my high side valve is suspect, I have been using the low side off the accumulator to vacuum test. If you get some various sized rubber stoppers from Lowes or the hardware store that are conical shaped, you can use those to plug the ends of hoses, ports in various parts so you can pull vacuum.

Right now I have vacuum on the whole system, minus the hard line which is on the garage floor. I just removed the orifice tube from the evaporator line and plugged it. I then plugged the opening of the condenser connection for the high side and then I pulled vacuum off the accumulator and letting it sit.

Doing this to make sure everything is playing nice now that I have tested all of the parts separately. Excessive, but I?m also the paranoid type when it comes to this kind of stuff.

[1991 Corvette ZR-1]

Installed the Dorman AC schrader plug and put a vacuum on the hard line while it?s on the garage floor. -30 inHg for about eight hours so I think we are good! My schrader valve removal tools show up tomorrow, so I think I am going to attempt to remove and replace the valve before I cap it and install back in the system.

If someone has the part for the valve core let me know. Otherwise, I think the larger of these valves will be the one I need to install.

[XfireZ51]

Installed the Dorman AC schrader plug and put a vacuum on the hard line while it?s on the garage floor. -30 inHg for about eight hours so I think we are good! My schrader valve removal tools show up tomorrow, so I think I am going to attempt to remove and replace the valve before I cap it and install back in the system.

If someone has the part for the valve core let me know. Otherwise, I think the larger of these valves will be the one I need to install.

I was only able to find tire valves for Schraders. Is the AC valve different from the tire valves?

[1991 Corvette ZR-1]

I was only able to find tire valves for Schraders. Is the AC valve different from the tire valves?

The valve cores appear to be different. The high side is a different size from the cores used for the pressure switches on the same hard line. I got a small assortment of valve cores to try. The factory high side core is on the left, the new one on the right. It wasn?t a perfect fit as the top was slightly larger than the opening to fit inside and screw in. So I filed it down slightly and it worked. It appears to seal when vacuum checking it but I may cave and seek a direct replacement that represents the original factory core or as close to it as possible.

I goofed on my vacuum testing of the hard line. I had the valve closed on the AC gauge while testing, so I only proved the gauge does not leak. So after replacing all the valve cores in this hard line, I still have a very slow leak. Next step after removing the pressure switches is submerging it in water and applying compressed air to it and watch for bubbles.

[1991 Corvette ZR-1]

Just a quick follow up the previous valve core replacement for the high side does NOT work. It is too tall and with gauge on it fully depressed it actually does not allow flow, which I never thought I would have to imagine that kind of scenario. I had to source a new valve core and it is Napa part number 209586. Exact replica for the old unit. About $4 for it and it seals nicely. It?s almost weird to have a high side valve that does NOT leak.

All of my valve cores leaked on the high pressure hard line. I will say this, this is a high mileage ZR-1, but by the time I go through every damn component on it, I will have restored some of the low mileage youth. Short of the engine internals, there isn?t anything I haven?t touched or serviced on this car.

[XfireZ51]

Thx 1991. Very interesting and informative. How would u say the proper valve compares w the omes you bought?

[1991 Corvette ZR-1]

Thx 1991. Very interesting and informative. How would u say the proper valve compares w the omes you bought?

The tiny valves in the assortment link I posted are a perfect fit for replacing the cores the switches connect to. The larger cores were not a correct size height wise. Once threaded in, the stem sticks out above the opening. Too tall. Even with the R134a adapter threaded on, the gauge connection would not fully seal due to the stem.

And it does flow properly. I held vacuum on the lines for several hours and then released it through the high side, so I know I have proper connection now. One of these days I might finally put refrigerant in.

[1991 Corvette ZR-1]

World?s slowest ZR-1 mechanic here. I found some valuable info from 2013, courtesy of Scottfab posting. These steps below differ slightly from the 1991 FSM recharge procedure on 1B1-23. See Below:

Charge the A/C System
1. With both Manifold Valves closed, hook up a can of R12 to the yellow middle hose (see Note #1 below).
2. Turn the can valve fully counterclockwise to open the valve.
3. With the can upright, crack the fitting on the yellow hose where it attaches to the gauge manifold to purge the air out of the hose, then re-tighten it.
4. You can now invert the can and crack the blue Low Side valve and charge until the pressure equalizes between the can and system (no more flow is felt or heard). Never open the Red High Side valve during the Freon Charging process.
5. Now start your car and set the climate control for Max cooling with blower on high. Ensure that the compressor clutch is engaged at this point (see Note #2 below). You can now charge the remainder of the first can with can in an upright position. Always charge with can upright when compressor is running.
6. Once the first can is in, (you'll know it's all in when you can shake the can and not feel any liquid sloshing in it) you can shut the low side valve and swap to the second can.
7. Remember to purge the yellow line again prior to charging.
8. Continue this until you have added the correct amount of Freon, per the FSM. Once the system is fully charged, shut off the compressor and allow High Side and Low Side pressures to equalize before disconnecting the gauge manifold from the system.
9. Once the manifold is disconnected, cap the high and low side fittings, reconnect the pressure cycling switch and you're done.


The FSM approach in a nutshell:

1. Start engine first before any refrigerant is added. Set AC mode control button to ?off?

2. With refrigerant can inverted, open valve and allow 16 oz through low side connection

3. After 16 oz added, engage compressor with controls and set blower speed to max. (May need to jumper low pressure cycle switch to turn on compressor during recharge process).

It sounds like the engine can either be on or off during the initial inverted can fill. Then when 16 oz is added, engage compressor on already running car, or start car and turn on compressor immediately. Regardless, can should never be inverted while the compressor is running, is what I have read.

There are 12 ounces in one can of R134A that I have. According to the FSM instructions, I will completely empty one can alone just on inverting it (upside down) and introducing to the system with the vehicle off. Then I need to have four extra ounces of inverted added THEN I can start the engine.

So 16 oz in a pound means I need one pound of R134A introduced to the vacuum tight system BEFORE starting. Then with the engine on, I use an upright can and add another full can of R134A.

That would put me at the following procedure:

1st can - upside down, open valve on low side, completely empty into system

2nd can - upside down, open valve on low side, extract 4 oz ONLY, measure with electronic scale to verify, set this can aside

Start car, engage AC compressor, blower to max setting

3rd can - Right side up, with car running, open valve on low side and introduce entire can for the full 12 oz.

This will give me a total of 28 oz of R134A in the system, which works out to 1.75 lbs.


Per an old post by -=Jeff=-

?R12 at 2.25 will be around 1.8lbs (at the high end) of R-134a

Typically R-134a is about 75-80% of the R12 fill.

reason the later cars are at 2lbs vs 2.25 is the added capacity of the parallel flow condenser vs the tube and fin condenser?

So that last .5 of an ounce I will have to gently add in I suppose. Sorry for the novel but just thinking out loud on my game plan before I start pumping refrigerant.

[-=Jeff=-]

That would put me at the following procedure:

1st can - upside down, open valve on low side, completely empty into system

2nd can - upside down, open valve on low side, extract 4 oz ONLY, measure with electronic scale to verify, set this can aside

Start car, engage AC compressor, blower to max setting

3rd can - Right side up, with car running, open valve on low side and introduce entire can for the full 12 oz.

This will give me a total of 28 oz of R134A in the system, which works out to 1.75 lbs.




You might not get 2 cans in without the car running, depending on ambient temp as well.. the vacuum up previously pulled and still have on your system with pull only so much in, you may need to finish can 1 and can 2 with the car running and the compressor running. I also found placing the can in hot water (higher than ambient) will help 'push' the refrigerant out of the can

[1991 Corvette ZR-1]

You might not get 2 cans in without the car running, depending on ambient temp as well.. the vacuum up previously pulled and still have on your system with pull only so much in, you may need to finish can 1 and can 2 with the car running and the compressor running. I also found placing the can in hot water (higher than ambient) will help 'push' the refrigerant out of the can

I just wanted to do a quick follow up that I charged the system. I may not have the optimal amount of R134A in the system because the vent thermometer was only reading 50 degrees on level 10 blower setting. Although that may be the best I can get? Wondering how other DIYers made out on their cabin temps. I had the setting on AUTO and blower on 10. Also have done Marc?s blower wire upgrade as well. Passenger side window was all the way up with the driver side slightly cracked.

[ghlkal]

1991, thanks for all the information :thumbsup:

I also found placing the can in hot water (higher than ambient) will help 'push' the refrigerant out of the can

That's a good idea, Jeff. I'm trying that the next time I need to put some in.

the vent thermometer was only reading 50 degrees on level 10 blower setting. Although that may be the best I can get? Wondering how other DIYers made out on their cabin temps.

That is better than I get. IIRC, my system is closer to 60* than to 50*.

[1991 Corvette ZR-1]

1991, thanks for all the information :thumbsup:



That's a good idea, Jeff. I'm trying that the next time I need to put some in.



That is better than I get. IIRC, my system is closer to 60* than to 50*.


Thank you, sir! Hopefully it can help someone else out along the way. Maybe the increased blower speed thanks to the added 12 gauge wire helps? If I remember correctly, the added 12 gauge wire with a fuse tied into the red blower module wire helps increase the air output by 4%. Maybe that extra 4% helped inch me closer to 50 degrees? I am also unfairly comparing this to a video posted on YouTube recharging AC by ChrisFix where his thermometer reads 43 degrees at the vent. That system on that vehicle was designed to work with R134A from the start whereas most of us are trying to make the old R12 systems work at that level in a conversion.

Though I have to wonder if the replacement condenser had different sized tubes for R134A or if they keep the reproduction parts the same tube diameter. Well to breathe some life into this old system, off the top of my head.

New condenser $100
Accumulator $25
O rings $5
New compressor lines $150
Compressor rebuild kit $20
Compressor oil with dye $20
Vacuum and gauges kit $150

So $470 worth of stuff and I would say round it up to $500 for little things like R134A adapters and the Dorman plug and other little bits. Not bad.

[1991 Corvette ZR-1]

40 degrees! Not using my thinking cap, the vehicle turning higher rpms cools better than at idle. On AUTO at speed, it got to 43 degrees with max blower and I was pleasantly surprised. For max cooling, per FSM, I selected circulate and with blower on 10 was I surprised to see the thermometer showing 40. Any worries about not having enough R134A in the system have been eased. At idle, the thermometer does creep up to 60 degrees, and the cooling falls off noticeably. Probably didn?t help that I had the clear top on. Very happy with the results so far.

Next on the list will be a replacement AC clutch as the final touch one day. The world?s slowest ZR-1 mechanic finally finished this project.

[-=Jeff=-]

when you guys are posting outlet temps of your AC, what is the Ambient Temperature? I found, the blower on mine gets good voltage, air velocity out the vents equlas that of my 2016 Charger, but the volume it not there. It will get the car cool on a hot day and the coolant temp hangs around 200-210 depending on type of driving ( traffic or moving)

[HAWAIIZR-1]

Thanks for sharing all your trial and tribulations. I found my AC was not cold and the compressor not engaging due to low pressure, but no codes. I charged with 1 can and bingo it works. But after I took off the line the low pressure Schrader valve is leaking. I fiddled farted with it trying to stop the leak, but I don?t have as new valve or the tool to change it. So I?m waiting on the valve core tool and the tool to replace the valve if needed without freon discharge. When it comes to AC I?m totally clueless, but I?ll learn with posts like these and YouTube.


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[1991 Corvette ZR-1]

when you guys are posting outlet temps of your AC, what is the Ambient Temperature? I found, the blower on mine gets good voltage, air velocity out the vents equlas that of my 2016 Charger, but the volume it not there. It will get the car cool on a hot day and the coolant temp hangs around 200-210 depending on type of driving ( traffic or moving)

Ambient temp out was 90 or 91 when I went for the test drive. Vehicle was in the garage and the thermometer read 89 sitting in the vent before turning on the AC. I used the vent right about the center console.

Thanks for sharing all your trial and tribulations. I found my AC was not cold and the compressor not engaging due to low pressure, but no codes. I charged with 1 can and bingo it works. But after I took off the line the low pressure Schrader valve is leaking. I fiddled farted with it trying to stop the leak, but I don?t have as new valve or the tool to change it. So I?m waiting on the valve core tool and the tool to replace the valve if needed without freon discharge. When it comes to AC I?m totally clueless, but I?ll learn with posts like these and YouTube.


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Haha well you will certainly get it done faster than I did! I believe the special tool that prevents discharge works very well. I used a generic removal tool due to the system being flat.

Anyone know what the rpm limit is for the compressor engaged? The highest I have had the engine up to was 4K.

[HAWAIIZR-1]

Ha ha. Well, the fat lady hasn?t sang yet. I saw a YouTube video about changing the valve core but the guy used the remover and found it was just loose. I will find out in a few hours when my order arrives.

Hopefully it goes smoothly. I still have to add more Freon, but in my case it seems it was just a slow leak from the Schrader valve core on the low pressure side.

1773317734


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[HAWAIIZR-1]

Update. I was fortunate that mine only needed a new valve core on the low pressure side. I added one more can of Freon and both static pressure and while running is perfect and cold.


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[mlipmd]

I would love to be able to use that tool and tighten up or remove my low pressure valve, but the way my accumulator tank and the fill tap is oriented, I can barely get the hose attachment from the can on there. The fill port is aimed at a 45 degree angle back to the right side and there is barely 2" of space in there. It looks like maybe there was an adapter added on to the accumulator fill port coming out near the top of the tank, maybe to convert my '90 car to R134?
Sorry the images are rotated 90* counterclockwise by the forum and I can't seem to fix that.

[HAWAIIZR-1]

I would love to be able to use that tool and tighten up or remove my low pressure valve, but the way my accumulator tank and the fill tap is oriented, I can barely get the hose attachment from the can on there. The fill port is aimed at a 45 degree angle back to the right side and there is barely 2" of space in there. It looks like maybe there was an adapter added on to the accumulator fill port coming out near the top of the tank, maybe to convert my '90 car to R134?
Sorry the images are rotated 90* counterclockwise by the forum and I can't seem to fix that.

Why do you have to deal with the accumulator and the schrader valve on there? Sorry, I'm clueless on AC so asking. I my low pressure schrader valve that had a slow lead was up by the coolant recovery tank. I connected the manifold gauge set to the low pressure (upper/fatter pipe) and the high pressure to the lower/skinny pipe). Then again, mine was simply just low freon because of the valve core leak and glad my was a simple task. I will buy a pump to pull vacuum in the future as needed. Best wishes.

[mlipmd]

Sorry, I don't know what year you have but the low pressure port on my '90 is located on the side of the accumulator tank where a retrofit adapter was added for the 134a refrigerant. The high pressure port is on the middle of the high pressure line. There is no port on any line near the coolant recovery tank.

[1991 Corvette ZR-1]

I would love to be able to use that tool and tighten up or remove my low pressure valve, but the way my accumulator tank and the fill tap is oriented, I can barely get the hose attachment from the can on there. The fill port is aimed at a 45 degree angle back to the right side and there is barely 2" of space in there. It looks like maybe there was an adapter added on to the accumulator fill port coming out near the top of the tank, maybe to convert my '90 car to R134?
Sorry the images are rotated 90* counterclockwise by the forum and I can't seem to fix that.

Yes, that is a R134A adapter that has been threaded on. If you were attempting to change the valve, that portion would need to be taken off before gaining access. Even then, as you said, clearance is an issue. You may get some extra space by removing the bracket which holds the accumulator in place to gently tilt it for more space to operate but the hoses are pretty stiff.

This is going to be an opinion some may not want to read, but due to the age of these components, the time may come when rebuilding most of or the entire system is necessary. My AC compressor leaked, all of the schrader valves leaked and my condenser was toast and rotting. Opening up the system meant I needed a new accumulator.

To get to the accumulator, you have to remove the compressor hose and low pressure hose. It is not going to happen. It is on there and the age of the parts does not help. There is a provision on the accumulator for a backup wrench while you attempt to remove the compressor hose. It will not hold as it is soft aluminum, you just round off the edges as the wrench slips around it. I had to hacksaw the connection off the accumulator still threaded into the compressor hose.

I then used my wrench on the compressor connection as the back up while I hit the other side with an impact wrench. It took a lot of force to break it free. Way more than you will be able to do leaning over the engine bay with each hand holding a wrench. The threads inside the compressor fitting were gone, completely wiped. The whole hose set was useless.

The passenger side of the accumulator actually broke free but took a lot of muscle and did not wipe the threads on the low pressure hose. That is good because had I needed to replace the low pressure hose, the connection that mates to the evaporator was SOLID. Same scenario there, not coming off unless it is cut off. Then you need a new condenser and you are draining coolant and tearing apart the car to get to that piece.

I guess what I am trying to say is this project is not for everyone. If you are going to dive in, pick up every single part outside of a new compressor before you jump in because it is a domino effect on parts if one is faulty or fights you to come off the car. I did it because I wanted to learn more about this specific system and I also do not trust any shops to do it right.

[mlipmd]

Since I now again have a major leak from my system (lost (2) 12 oz. cans of refrigerant in 48 hrs.) after filling it up, and since it could be the compressor that is leaking, and to replace that, if so, requires the plenum to come off, or it could be any of the other major parts, or even an O ring, I don't feel like tracking this down when there are experts who can do this. And none of those old parts are going to be able to move easily, and I don't have the equipment needed to evacuate and flush and adequately refill the system, in addition to tracking down the parts. So sometime next week I will take a drive and bring the car back to South Georgia Corvettes and have Aaron Scott and his AC associate down the street look at it and repair/replace what's necessary. Then again I'll be set for the hot summer down here to come. Sometimes you have to refer the job to the experts.

[HAWAIIZR-1]

Sorry, I don't know what year you have but the low pressure port on my '90 is located on the side of the accumulator tank where a retrofit adapter was added for the 134a refrigerant. The high pressure port is on the middle of the high pressure line. There is no port on any line near the coolant recovery tank.



Got it. I have a 95. Thanks.


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[Corvette95]

Ha ha. Well, the fat lady hasn?t sang yet. I saw a YouTube video about changing the valve core but the guy used the remover and found it was just loose. I will find out in a few hours when my order arrives.

Hopefully it goes smoothly. I still have to add more Freon, but in my case it seems it was just a slow leak from the Schaefer valve on the low pressure side.

1773317734


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I saw this post last week and was going to reply a tire valve core remover will work on the a/c schrader valve but then I saw where you said you were waiting on a tool so you didn't have to remove the freon... I have never seen this, will this this go onto either the high or low port and allow you to change the schrader valve core without evacing the freon or am I misunderstanding entirely. I would like to get a set if that is how they work. I still have original r12 and r134a in both of mine and believe my low pressure valve has a super slow leak (134a). It takes about a half a pound every two years or so ( I know, worse problems to have) but more info would be appreciated!

[HAWAIIZR-1]

I saw this post last week and was going to reply a tire valve core remover will work on the a/c schrader valve but then I saw where you said you were waiting on a tool so you didn't have to remove the freon... I have never seen this, will this this go onto either the high or low port and allow you to change the schrader valve core without evacing the freon or am I misunderstanding entirely. I would like to get a set if that is how they work. I still have original r12 and r134a in both of mine and believe my low pressure valve has a super slow leak (134a). It takes about a half a pound every two years or so ( I know, worse problems to have) but more info would be appreciated!



Yes, that is exactly what it does. It?s pretty slick and I?m glad such a tool exists. Here is a video of how it works.

https://youtu.be/wkPxxUO_40Q

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[Jagdpanzer]

Clever tool
Thanks Craig for sharing.


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[mlipmd]

Question - is the high pressure Schrader valve on a '90 removable with that tool or does the whole unit containing the valve (which is screwed on to the high pressure line) need replacement as the valve cannot be separated from that?
I definitely have a leak from that valve as I can see it and hear it after I refilled the system and took the plastic cap off.
But I dropped the cap right there and damnifI can find it right there or underneath the car. I wanted to try and find a metal cap anyway, good luck with that too.
If that tool will remove the valve on my car, where's the best place to get a replacement, NAPA? My car has been converted to R134a by seeing the adapter on the accumulator tank low pressure fill port, so I assumed that high pressure Schrader was replaced as well?

[HAWAIIZR-1]

Question - is the high pressure Schrader valve on a '90 removable with that tool or does the whole unit containing the valve (which is screwed on to the high pressure line) need replacement as the valve cannot be separated from that?

I definitely have a leak from that valve as I can see it and hear it after I refilled the system and took the plastic cap off.

But I dropped the cap right there and damnifI can find it right there or underneath the car. I wanted to try and find a metal cap anyway, good luck with that too.

If that tool will remove the valve on my car, where's the best place to get a replacement, NAPA? My car has been converted to R134a by seeing the adapter on the accumulator tank low pressure fill port, so I assumed that high pressure Schrader was replaced as well?


I have no idea about your situation and R134 conversion on your car, but the kits that I bought had the tool and caps for both R12 and R134, high and low pressure side. No aluminum caps, but I am sure you can find those if you have to have them. My 95 came with black plastic so I was happy to replace with red and blue despite cannot screw them up since different size connection. There are better and worse tools price wise, but you get the idea from Amazon or otherwise search depending on how much you want to spend, how quick, and quality or origin of tool:


gohantee 17Pcs Air Conditioning Valve Core Kit Schrader Valve Cores Accessories A/C R12 R134a Refrigeration Valve Stem Core Rmover Tool HVAC System Seal Caps Kit https://www.amazon.com/dp/B07T2RBHR3/ref=cm_sw_r_cp_api_i_37KHAEYMGYVSAXZ5D3TE

Lichamp Automotive AC R134A R1234YF Valve Core Remover and Installer Tool Set, for Standard and JRA Valve Core Couplers https://www.amazon.com/dp/B07QVF2V2R/ref=cm_sw_r_cp_api_i_PF5MTKPXXF6244NK71F8?_encodin g=UTF8&psc=1


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[HAWAIIZR-1]

Clever tool
Thanks Craig for sharing.


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You are welcome Phil. It was a lifesaver for me since I don?t have a vacuum pump yet and still had Freon in my system, just low for the leak at the valve confirmed with spit lol?..


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[mlipmd]

I got a simple valve core removal tool because my system is totally empty and don't need that fancy one. I can grasp the 2 wings on the valve core and rotate it but it doesn't seem to unscrew, won't come up and out, even if I grasp it with a surgical forceps. I'm wondering if someone crossthreaded it when installing it, so it's now in there forever. Shouldn't that valve core be removable or does that whole assembly with the core inside unscrew from the high pressure line and is replaced as a unit with the valve core inside?
Someone give me a suggestion on how to remove the core.
If I can't get it out I either have to source the whole high pressure line or cut it and weld/braze in a new segment with a valve inline.

[mlipmd]

Like I also posted on the Corvette forum -
Never mind, got it out. Google is your friend.
When all else fails, pull/push it harder, came out by pulling it with a pair of pliers, didn't seem to strip any threads, new one from O'Reilly's a perfect replacement.
Sucked out the system for about 2 hours, no leaks after 1/2 hr.+, refilled it and all is good right now.
It was 95 driving to the store today down here, not a lot of fun with no AC, but tomorrow will be a better day.

[1991 Corvette ZR-1]

Does anyone know the rpm limit, if any for the compressor on while driving aggressively? I have not been brave enough to go for a 7K rpm trip with the compressor engaged. I have limited the fun to 4K rpm before shifting.