AC restoration questions, '93 Mazda RX7

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pete_89t2
Posts: 27
Joined: Thu May 04, 2017 9:38 am

Re: AC restoration questions, '93 Mazda RX7

Postby pete_89t2 » Sun Jan 10, 2021 8:04 am

Well I managed to get an electronic leak detector and found my leak yesterday - it was the brazed joint I made between the male O-ring fitting and the pictured compressor fitting pipe, discharge side. Heck, once I added some refrigerant, I didn't need the sniffer to find the leak - the compressor lube with UV dye made the leak pretty obvious.

AC Compressor Discharge Pipe & Fitting 1.jpg
AC Compressor Discharge Pipe & Fitting 1.jpg (156.68 KiB) Viewed 41 times


I salvaged that pipe and the suction side fitting from a used OEM hose set. After removing the OEM beadlock ferrules, my original plan was to just stick a #8 reduced barrier hose over the barb end of that discharge pipe and crimp on a new ferrule, but I couldn't get the hoses & ferrules to fit over the barbs on either the suction or discharge pipes - apparently Mazda used a slightly larger ID hose than the current #8 & #10 reduced barrier hose standards? Same hose I purchased fit easily with no struggle on the new #8 & #10 fittings I got. Gave up on trying to force the hoses to fit, and went to plan B - brazing aluminum male O-ring fittings on the end of each aluminum pipe. While my brazing work resulted in mechanically solid connections on both parts, only the suction fitting tested gas-tight.

I'm a newbie to brazing AL, are there any suggestions on how to get a gas tight seal when I do-over the discharge side? So far I un-brazed the discharge pipe from the male O-ring fitting. Pipe end cleaned up well, and should be re-usable. Worst case, I still have enough length on it where I can cut off 1/4" or so of the brazed end if need be. The male O-ring fitting got too trashed upon removal to reuse, so I ordered a new one.
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JohnHere
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Location: South Carolina Upstate - USA

Re: AC restoration questions, '93 Mazda RX7

Postby JohnHere » Sun Jan 10, 2021 1:43 pm

pete_89t2 wrote:Well I managed to get an electronic leak detector and found my leak yesterday - it was the brazed joint I made between the male O-ring fitting and the pictured compressor fitting pipe, discharge side. Heck, once I added some refrigerant, I didn't need the sniffer to find the leak - the compressor lube with UV dye made the leak pretty obvious.
Glad you found the source of the leak.
pete_89t2 wrote:I'm a newbie to brazing AL, are there any suggestions on how to get a gas tight seal when I do-over the discharge side?
Techniques for a gas-tight seal is to ensure that you heat the parts and not the brazing rod so that the rod material flows smoothly into the heated joint. Typically, the parts need to be heated to around 700 degrees F, which depends on the melting point of the brazing rod you're using. Check the packaging for that info. Be sure to clean the parts well with a small wire brush with brass bristles. And keep the torch moving. Otherwise, you risk melting the parts themselves rather than just the rod. MAP gas and air/acetylene torches will heat the parts quicker than propane, so extra care is needed when using the former.
pete_89t2
Posts: 27
Joined: Thu May 04, 2017 9:38 am

Re: AC restoration questions, '93 Mazda RX7

Postby pete_89t2 » Mon Jan 11, 2021 5:46 am

JohnHere wrote:Techniques for a gas-tight seal is to ensure that you heat the parts and not the brazing rod so that the rod material flows smoothly into the heated joint. Typically, the parts need to be heated to around 700 degrees F, which depends on the melting point of the brazing rod you're using. Check the packaging for that info. Be sure to clean the parts well with a small wire brush with brass bristles. And keep the torch moving. Otherwise, you risk melting the parts themselves rather than just the rod. MAP gas and air/acetylene torches will heat the parts quicker than propane, so extra care is needed when using the former.


Sounds like I just need a bit more practice then, as I pretty much did all of the above. The AL brazing rods I used were these guys, available locally: https://www.homedepot.com/p/Bernzomatic ... /203710179

I was using a MAP gas torch, and applying the heat to the parts until they were hot enough to melt the brazing rod so it would flow into the joint by capillary action. I only applied heat to the parts, periodically touching the part with the brazing rod to test when if it was up to melting temp yet. The packaging for these rods claim a melt point of about 725~750*F, IIRC, and that you don't need to use flux with them. Some of the reviews of these brazing rods say they work much better when used with a proper AL brazing flux, so I may try using flux next time. Any recommended fluxes for AL brazing? Seems that none of the hardware stores local to me carry fluxes for AL brazing.
Dougflas
Posts: 356
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Re: AC restoration questions, '93 Mazda RX7

Postby Dougflas » Mon Jan 11, 2021 7:28 am

Take the ass'y to a local welding shop and have them TIG weld it and be done with this.

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