How to repair Pinhole Leak in Aluminum Tubing?

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Old 08-02-05, 06:04 PM
NeedSomeACHelp
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How to repair Pinhole Leak in Aluminum Tubing?

My system is losing freon. AC tech came by today and located a leak in a small segment of aluminum tubing just before the coil. The leak was detected with a sniffer and then using soap bubble method. The soap bubbles clearly showed a very small, yet visible, pinhole leak.

The tech says it is not possible to weld (solder?) on the aluminum tube.

My question---does anyone know of a simple and inexpensive method to seal the pinhole leak, either with some sort of clamp or some sealant material, that will withstand the pressure and not be degraded from exposure to freon inside the tube?
 
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Old 08-02-05, 06:19 PM
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Aluminum

I have seen solders which are supposed to work with aluminum but I have never been sucessful in using them. I have cut the tubing & used a flare union on an emergency basis. If done, the flares have to be perfect. In general, your tech is right.
 
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Old 08-02-05, 06:27 PM
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Thanks.

He did mention a flare union, but that would require complete evacuation of the system's freon, which he just refilled today, so I was looking for a method that could be performed with the system "live". (I was even thinking of trying to wrap the segment with the pinhole with a piece of aluminum foil--to maintain similar metal-to-metal contact--- and then applying a ring clamp around it in effort to at least limit the escape of freon).
 
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Old 08-02-05, 06:45 PM
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HVAC supplier nearby has an epoxy for this purpose. Never used it, though.

Applied with a torch until it changes color.

Probably have to evacuate the system, which isn't a big deal. I don't think any type of sealant would set up properly with a charge in the system.

Foil and hoseclamps probably not a good idea.
 
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Old 08-02-05, 06:45 PM
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Leak

Any type of permanent or semi-permanent repair is going to require evacuation of the system.
 
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Old 08-02-05, 06:54 PM
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I would feel very comfortable using an epoxy like JB weld. In some units they join copper tube to aluminum with an epoxy and crimp connection. If there was no pressure and the aluminum was clean and free of oil, I would bet the epoxy would seal and last forever. There is also a repair that is fast and easy and it is made by North Sea Resins (northsearesins.com). They are right in my back yard and quite a few guys in my area use the system for pinhole leaks in copper pipes. I have seen it work but haven't used it myself. Good luck. I would be hesitant to try to solder or weld it.

Ken
 
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Old 08-02-05, 07:21 PM
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KField - Thanks. I'll look into these ideas.

Do you know if the North Sea Resins product is applied with the system evacuated or could it be applied while the system is energized with freon under pressure?
 
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Old 08-02-05, 07:32 PM
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I don't know anything...

But I can't believe that you can repair any "leak" properly without first relieving the pressure from the system. (just my opinion, though)
 
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Old 08-02-05, 08:04 PM
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Red face

NeedSomeACHelp,

I am sorry to tell you that there is no repair out there that won't require a service call to reclaim the refrigerant from the system.
I can also tell you that I have had a fair bit of experience with epoxies on aluminum in old systems and the success rate beyond a couple of months is low.
Even if the epoxy repair were attempted, the refrigerant would need to be removed before patching and the cure time would require the tech to go and come back.
Some epoxies advertise a short cure time, but the failure rate was higher if not left overnight.
There are also solders available for aluminum but the problem with them is that when the tubing is heated, oil that is coating the inside of the tubing tends to migrate to the hole and mess up the solder.

The main issue though is the wisdom of the "tech" in adding refrigerant to a system with a known leak.
Someone should inform this person that the days of "topping up" a leaky system are over.
Here and I suspect where you are this practice is illegal, not to mention a big waste of your money.

You would be doing the right thing by getting him back to replace the component that is leaking.
Be sure he reclaims the refrigerant and does not charge you for gas he shouldn't have installed in the first place.
 
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Old 08-03-05, 04:09 AM
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I will agree that you may buy some time with an epoxy repair but usually when they get a pin hole there are more following behind ready to surface. If your a/c is anywhere near 15 years old I would be very hesitant in replacing just the coil.
 
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Old 08-03-05, 05:12 AM
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I would have to agree with the others who have tried the epoxy method since I have not. You may not like what you hear but it will save you aggravation and money in the end.

Ken
 
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Old 08-03-05, 10:38 AM
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THNAKS for all of the input.

A few comments on some of the previous advice:

1. The tech topped off the freon because he was in a hurry and did not have time to attempt a prmanent or semi-permanent repair. He concluded that "topping off" would get me cool again immediately and that the leak is so small, it would last me through at least the end of this season. We'll see. (My best description of the rate of leakage is that the "bubble test" formed a small bubble about 1/8" in diameter every 5 seconds, then burst, then another bubble formed and repeated itself---etc.)

2. The tech says that the only alternative he recommended was to pull the unit and replace the coil. Given the age of the unit (12 years), he said my money would be better spent replacing the entire unit ($2,200) rather than try9ing to repair an old coil or replacing only the old coil with a new one. Therefore I was looking for a simple fix to a small pinhole leak to squeeze a couple of more years of life out of the unit.

3. The Tech said that if the leak does not increase, I can probably get by for a long time simply "topping off" maybe once per year. I am not sure if that is legal or ethical but he seemed to think that was an operating strategy that could save me from forking out for a new unit @ $2,200 for a few years. It would cost me about $150 per year to top off.

4. Sounds like everyone is unanimous---no temporrary repair is possible without evacuation of the system. Thanks for the advice, everyone.

5. I am still open to other ideas for a temporary repair. I am still inclined to try a piece of aluminum foil wrapped neatly several times around the leak with a hose clamp holding down some pressure in effort to seal off the pinhole. Why would that not be a "no-risk" effort to slow down the leak?? In other words, what is the negative risk?
 
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Old 08-03-05, 04:01 PM
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If you checked for the leak with the unit off, you may be surprised how much worse the leak will be when the pressure is on the system. Good luck.

Ken
 
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Old 08-03-05, 04:06 PM
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How about this?


http://durafix.com/
 
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Old 08-03-05, 04:21 PM
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I have tried the material in the last post and might recommend this instead http://www.dubblebubble.com/

You now have a leak of known size and have not yet contaminated the refrigerant or rendered the unit non-functional. You should consider any negative side-effects of all possible remedys.

Ken
 
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Old 08-03-05, 04:53 PM
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The link provided was for a wonder solder that relies on scraping away the oxidation on aluminum while applying the filler before the material can re-oxidize.
I have a drawer full of those kits. Want one?
They will work...................sometimes.
There is a distributor network for this type of product that specialzes in trade show demonstrations.
I've participated in the demo and successfully soldered the two bits of aluminum.
Went home and repeated the demo with only limited success.
Tried it on a practical application and it was pretty useless, especially for withstanding pressure.
Those kits are good for the economy but only for the seller.

NeedSomeACHelp,

I think your mechanic is in a state of denial that the refrigeration and airconditioning industry has changed.
Perhaps some of my southern cousins will verify this for the US but it is now unlawfull to refill a system when there is a leak and not making an HONEST attempt to locate it.
Professionals in the industry are faced with regulations that if violated put their certification at risk and will comply with rules that are in place.
Hacks will do what your tech has done.

This still leaves you with a system that will fail.
If the leak was at the evaperator coil a replacement is not that expensive.
Although there are more efficient systems available, a twelve year old system could still have a lot of life left.

As far as a temporary fix I would say that a good heavy piece of rubber held tight with a hose clamp would be good.
It won't stop or slow the leak but will be something you can do.
 
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Old 08-03-05, 05:04 PM
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I will summarize the advice you were seeking and say that no temporary repair is possible.

If you need any info regarding a replacement unit you may post a new question.

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