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See the video on the this page https://www.machinemart.co.uk/p/aluminium-repair-starter-kit/

Fix your own aluminium cylinder head where pitted on the compression gasket land due to a blown head gasket / easily fix holed aircon pipes? Would you have faith this would work?

I have a leaky aircon pipe (not on a P38), haven't looked where the leak is yet but the missus could hear it was near the back wheel. When I get time plan is to pressurise the AC system (with CO2 or LPG because DIY AC gas refills are expensive, I don't have nitrogen and don't want to shove water vapour in with compressed air), locate the leak, remove pipe and hopefully use this stuff (cheaper from Ebay) to braze and fix it. If that works I might let an AC firm suck all the gas out and refill... but wonder if it CO2 / LPG would be a problem for their machine?

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Got to be worth a try, you've lost very little if it doesn't work. I'd use compressed air to check for the leak. I know water vapour would get in there but that is what would be in there if the system has been apart anyway so shouldn't harm the vacuum machine when they evacuate it before refilling.

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Yeh and I suppose there'll be a bit of water vapour in there now anyway with it having the leak low down under the back of the car. Can't be a massive leak, I got the aircon working for a few minutes just using a Halfords recharge kit but knew it was going to fail when she heard the hissing (better hearing than mine, 10 years younger + didn't spend 20 years DJing).

Have to wonder what effect LPG or CO2 would have on their machine... imagine them assuming it'll just have R132 and air in there until smoke starts pouring out of the machine lol, don't see it being a problem but can't be sure, or may be a problem when they come to recycle the gas... although nitrogen can't be a problem.

Do you reckon the DIY head repair would work using this stuff?

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Another reason for thinking of using CO2 or LPG is that my large compressor broke years ago and I never bothered fixing it, started preferring electric tools rather than pneumatic for LPG work.

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Some refrigerants are flammable, and the kit used to work on them needs to be up to the job. R134a, which I'm guessing the vehicle in question uses, is not, and is what most places will be set up for. I wouldn't be connecting any of my kit up to a system that has an unknown quantity of LPG floating around in it.

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How do you know what's floating around in any aircon system though? Must be a few people that have read on the net that propane can be used in some aircon systems and tried filling R134 systems with it.

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It won't work on an R134a system for long, the Propane will dissolve the seals and it will all leak out. It can be used on an old R12 system but as the connections are different a modern evacuation unit won't connect to it anyway.

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Different connections, also I think R134 has a higher working pressure than propane or R12 systems so an R134 system might not work on propane even if the seals don't fail?

Seals failing are reason I now won't pressure test with LPG... I'm surprised I was lax on that, thanks!

Still the hypothetical scenario where someone turns up at an AC shop with a none working R132 system full of LPG... Must have happened to someone, I was considering taking the AC fill pipe off the Halfords kit and connecting to an LPG source to pressure test, others will have read a bit on the net about some AC systems using propane and thought of chancing filling their system from a Calor bottle (maybe not to leak test but to recharge). What happens regards the AC machine and if the machine is broken what are the AC mans options (machine warranty, recourse on vehicle owner, etc)? I know machines recycle the gas and oil that they extract, does this mean they pump it into someone else's car or store it to send off for recycling?

Besides flammable, aren't some AC gases carcinogens if they come into contact with a flame or UV?

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What i've done before (after speaking to someone else about it) is to connect the system from a working car to your non working one, i used high pressure (Donor) to low pressure (receiving) car, just with a suitable pair of connectors and hose brought off eBay.

That was enough to put approx 1/2 of the required charge into the empty car (having repaired a known common leak problem) and was enough to make the a/c work (was mostly wanting to check if it started to leak out anywhere as it was non working when i brought it, and on connecting the valve it was clear the system was completely empty as well as a tiny puff came out and nothing more).

I had it recharged and that managed to remove 310g of the 750g required charge, so you don't need a lot really (I've had it recharged since then, so know how much went across). The donor car was on its way to being scrapped anyway, so it just saved having to deal with most of the gas out of it at the same time. Only thing i'd recommend is to get longer hoses than I did if you can, as i had to have both of them almost touching to connect up. It may also help to run the compressor on the donor vehicle (it seemed to in my case) to get as much as possible out. The bonus being that as long as you've taken it from a clean system then the gas is the right stuff. I did also use the connector to put a bit of PAG oil into it at the same time (before the gas obviously!) as i wasn't totally sure what would go across.

I'd only want to do that on a working donor system though, as you don't know what else might be in there if its not working (bits of failed compressor etc)

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Lpgc wrote:

Different connections, also I think R134 has a higher working pressure than propane or R12 systems so an R134 system might not work on propane even if the seals don't fail?

Seals failing are reason I now won't pressure test with LPG... I'm surprised I was lax on that, thanks!

Still the hypothetical scenario where someone turns up at an AC shop with a none working R132 system full of LPG... Must have happened to someone, I was considering taking the AC fill pipe off the Halfords kit and connecting to an LPG source to pressure test, others will have read a bit on the net about some AC systems using propane and thought of chancing filling their system from a Calor bottle (maybe not to leak test but to recharge). What happens regards the AC machine and if the machine is broken what are the AC mans options (machine warranty, recourse on vehicle owner, etc)? I know machines recycle the gas and oil that they extract, does this mean they pump it into someone else's car or store it to send off for recycling?

Besides flammable, aren't some AC gases carcinogens if they come into contact with a flame or UV?
Your reply appeared after i began replying above!

You definitely don't want to inhale r134 via a heat source (eg a cigarette) it does something nasty, not sure its just carcinogenic I seem to remember there is other risks. This seems to suggest its poisonous in that state > https://www.hella.com/techworld/uk/Technical/Car-air-conditioning/Car-refrigerant-oil-filling-quantities-2114/#

They recycle the gas, not the oil (thats collected on the ones I've seen, but not reused). They have to deal with moisture so must have a way to remove the unwanted material from it, not seen inside a machine to tell, but there must be a waste container of some sort there.

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I've used the sort of low temperature aluminium braze-welding sticks mentioned in the first post before. Maybe 30 years ago. Lumiweld brand I think. The stuff does work but things have to be scrupulously clean and getting reliable results is bit of an art form. I only repaired a couple of lumpy castings. Zilch confidence in successfully fixing pipes or thin material without plenty of practice.

Funnily enough what I used back then was said to be the new improved second generation material. The stuff seems to appear and disappear on the retail market in a fairly regular several year cycle with new band names each time round. Always the new improved second or third or (how far can you count) generation stuff far better than the last time it was popular.

Hmmn.

Nothing greatly magic about it. One component of the stick locally reduces the melting point of the aluminium alloy. So all (!) you have to do is to get the aluminium alloy hot enough to melt the stick onto it but not so hot that the underlaying material melts and a bond is formed. As always with aluminium there is the pesky detail of getting rid of the oxide film so metal to metal contact between the substrate and melting repair stick can occur. Stuff I used needed vigorous scratching with a stainless steel probe under the melted stick material to properly initiate bonding. Not too hard on a decent lump of casting but on thin sheet or pipe .... Samples in the video look far too clean for real life and are probably specially chosen materials too.

Gotta be a reason why this stuff isn't mainstream.

Clive

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Thanks for replies. I probably won't connect another cars's AC system to this car's, don't have a vehicle with a running engine (to run compressor) to scrap and depleting a good car's AC charge defeats the object when could just put a partial charge in from a Halfords bottle without having to buy/make a long line. Something to remember though and I'll probably try this sometime in future in a different situation.

I saw some other videos on Youtube that make brazing the AC pipes look similarly easy as in the MachineMart video but on thin AC pipes, the surface tension of the melted rods almost magically spanning and filling holes without filling the pipe with braze... which is what I'd need because the pipe I need to fix has another pipe running inside it (visibly one pipe runs to rear AC because the second pipe runs inside it), don't want to fill the void between interior and exterior pipes.

Started with doubts about how well a brazed repair would hold, then on how difficult it would be to do the job (skill). The videos made me more confident in both respects, now still confident on braze effectiveness but a bit less confident in terms of skill, Clive's points agreed with my initial doubts. I will be trying it and if I can't fix the pipe could maybe lower ambition and braze the inny-outy pipe shut so at least the front AC will work or increase ambition and run two pipes to a different rear evaporator. Seen some videos where they make brazing fittings (such as for crimping rubber AC pipes to) onto AC pipes look even easier than repairing holes..

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Even without the compressor running you will get some transfer, certainly enough to detect a major leak with. But it does rely on having another vehicle that you don't need the AC gas in all the same, so if you haven't got that at present then not an option.

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BrianH wrote:

You definitely don't want to inhale r134 via a heat source (eg a cigarette) it does something nasty, not sure its just carcinogenic I seem to remember there is other risks. This seems to suggest its poisonous in that state > https://www.hella.com/techworld/uk/Technical/Car-air-conditioning/Car-refrigerant-oil-filling-quantities-2114/#

That's me buggered then lol!

I do have a car here with charged AC system that will be scrapped at some point so could make sense to do as you say with the pipe between cars, I plan on cutting some AC pipe from it to practise brazing with. Still I suppose I'd need to make up the line to connect cars and the AC system on the car to be repaired will be open to the elements when I remove the pipe to fix it. How did you make the line Bri and does it run between low pressure ports or high to low port?

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Extrapolating from my memory of doing larger castings the major difficulty when using the magic braze-welding sticks on thin material is likely to be controlling the temperature of the substrate.

Given the good thermal conductivity of aluminium it ought not to be too difficult to keep the surface of a large lump at, or slightly above, the right temperature without melting everything. But I did come close before getting the knack and realising that it doesn't need to have as much heat poured in as you might think. With a thin pipe there is very little alloy to absorb and transmit heat so the difference between "temperature OK" and "Ooops, melted it" will be small in the practical terms of how much to turn the torch flame up, how close to hold it and how long to heat for. Pity there are no colour changes, like when heat treating steel, or indicator substances, like soap on hard alloy sheet to indicate its hot enough to bend, to help. Wonder if there is some mileage in getting creative with a cheap IR thermometer when practicing. Something I might try if I ever use the stuff again.

Up to a point it will get under the oxide layer and any minor contamination. Floats up as a sort of slag on top which has to be removed with the stainless steel wire brush and/or abrasive paper provided once things have cooled off. Still have to get under the oxide or contamination for the bonding to start the process. As I recall it the temperatures involved with oxide or contaminated surfaces tend to be higher and its all rather harder. Once you have that first layer on it all goes much easier. Equivalent to tinning copper, brass or steel before soldering I guess.

Yet another addition to my list of jobs and techniques I need to do 3 times before getting the hang of it enough to know whats going on. 4 th time lucky might still be a mess but at least I'd know why.

Clive

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Lpgc wrote:

BrianH wrote:

You definitely don't want to inhale r134 via a heat source (eg a cigarette) it does something nasty, not sure its just carcinogenic I seem to remember there is other risks. This seems to suggest its poisonous in that state > https://www.hella.com/techworld/uk/Technical/Car-air-conditioning/Car-refrigerant-oil-filling-quantities-2114/#

That's me buggered then lol!

I do have a car here with charged AC system that will be scrapped at some point so could make sense to do as you say with the pipe between cars, I plan on cutting some AC pipe from it to practise brazing with. Still I suppose I'd need to make up the line to connect cars and the AC system on the car to be repaired will be open to the elements when I remove the pipe to fix it. How did you make the line Bri and does it run between low pressure ports or high to low port?

I brought the bits of eBay - Examples below

https://www.ebay.co.uk/itm/R134a-Auto-Quick-Coupler-Bass-Adapters-Low-High-Side-AC-Manifold-New-SU/183151899017
https://www.ebay.co.uk/itm/R134a-R22-404-502-Manifold-Gauge-HVAC-AC-Refrigeration-5ft-Test-Charging-Hose/263565622043

I think the hose I got wasn't as long as those 5ft ones, its more like 2ft long the one i was using, hence it made it required the cars being so close (may be easier on yours as the ports maybe more accessible). But that was going from a Focus to a Galaxy, The ports on both of them were hardly ideal for the task but it worked.

If you buy two sets of the connectors you can run from either port to either - i don't know how much of a difference that would make to how much you get (I would assume that given long enough the pressure in both should become equal, so you should get half of the amount you started with less whatever is stuck in the pipes. I did run the compressor on the donor mainly to try and speed it up a bit as both cars had engines that would start (failed clutch on the Focus meant the previous owner of it changed his mind once it was at my workshop about repairing it as it had couple of other faults, and two holes we later discovered in the rear arches that he didn't know about). I'd suspect any combination of high/low linking should work to at least allow some gas to flow across, Though you might not get any oil with it, but for leak testing it was certainly easier than the previous attempts I've had by using the garage to nitrogen test it.
Nowhere round here seems to actually do air con repairs, though plenty of places will recharge it, hence they seem to be constantly out of gas).

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Also - I'd have a look if I were you what bit of pipe is causing the leak if you can find it, As that may effect how you want to repair it anyway (There are kits to go over a simple pipe called splice-lok - Don't think its suitable in your case due to the inner pipe unless its very close to the end of a piece where you can remove the outer from the inner pipe). Those don't work too well if the pipe isn't straight though.

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Thanks Clive and Bri.

In the vids they just keep testing to see if the rods will melt when they touch the aluminium, though I take your point about a thin pipe could be cool at the edges but quickly get too hot and melt where heated. I picture going up and down quite a length of the pipe heating quite an area around the leak while testing with rods to prevent overheating a small area. Yet to see if it'll work lol!

Couldn't slide anything like a pipe over the outer AC pipe because it's in sections with wide fittings at each end, couldn't cut it to slide anything from the cut side because it has the inner pipe. .

Usually less pressure on the low side of an AC pump when running than there is with AC system turned off?

Seems plenty firms will recharge AC but very few will get involved in fixing it. Years ago I had a problem with AC on a Grand Voyager, it failed the vac hold test at Charlie Browns. Staff there pointed me to a guy next door who they said could repair AC systems so I left it with him for the day expecting him to stick fluorescent dye in it and tell me exactly where the leak was. When I returned he hadn't found the leak or put any dye in it, he simply told me there was a leak somewhere on it. Heated argument and I wouldn't pay him... WTF did he think I'd gone to him for when Charlie Browns told me the same very basic info for free. Think he just thought he'd chance having my trousers down, no chance lol. I really have a problem with people who do that sort of thing, there are plenty like it in the field of LPG too.

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Lpgc wrote:

Thanks Clive and Bri.

In the vids they just keep testing to see if the rods will melt when they touch the aluminium, though I take your point about a thin pipe could be cool at the edges but quickly get too hot and melt where heated. I picture going up and down quite a length of the pipe heating quite an area around the leak while testing with rods to prevent overheating a small area. Yet to see if it'll work lol!

Couldn't slide anything like a pipe over the outer AC pipe because it's in sections with wide fittings at each end, couldn't cut it to slide anything from the cut side because it has the inner pipe. .

Usually less pressure on the low side of an AC pump when running than there is with AC system turned off?

Seems plenty firms will recharge AC but very few will get involved in fixing it. Years ago I had a problem with AC on a Grand Voyager, it failed the vac hold test at Charlie Browns. Staff there pointed me to a guy next door who they said could repair AC systems so I left it with him for the day expecting him to stick fluorescent dye in it and tell me exactly where the leak was. When I returned he hadn't found the leak or put any dye in it, he simply told me there was a leak somewhere on it. Heated argument and I wouldn't pay him... WTF did he think I'd gone to him for when Charlie Browns told me the same very basic info for free. Think he just thought he'd chance having my trousers down, no chance lol. I really have a problem with people who do that sort of thing, there are plenty like it in the field of LPG too.

Sounds very much like my experience of both of them round here - Hence why I tried what I did before resorting to replacing the condenser which would have been the next step (dryer on that is part of the same). The garage I usually use for MOT work will do aircon regas only anyway, so no chance of him doing anything more with it.

The local LPG fitter is/was of a similar manner, on asking about a uklpg register entry he said he'd have to inspect it (OK), rectify anything wrong (OK), Then inspect it again (surely part of the rectify step?) and then it still might fail (WTF?). Though having seen the state of one of his installs one of my neighbours had on a Toyota Hiace Van I can see why someone else might fail his workmanship as it didn't look good (Reducer mounter at 45 degree angle off the right way up along with other things)

Was wondering if you could get away with one of these things - https://www.walmart.ca/en/ip/AGS-AKACRK-045C-0-62-0-75-Tube-Air-Conditioner-Repair-Splice-Lok-Kit/PRD1RUMX5XGSQO1 Though thats probably not relevant as i now can't find anyone here selling it at a sensible price (there were around £20 when i brought one, but the only ones now on eBay are in the US.) Would only work if you could take the outer off the inner line, which you can't by the sounds of things (I do wonder why its like that though?)

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The splice could work, not seen those before. I'll have to see where the leak is first and check diameter, not measured it but seems wider than 3/4"