Having a crack at aluminium brazing .. Now with pics!

[mike-s]

Unfortunately I haven't been able to complete doing this due to the oil pan being a right prick to remove & wasting a lot of my time tonight, but i'll put up the little that i have done thus far. One thing that isn't shown is the 2 or so hours spent getting the plastic, exhaust and radiator off to get unimpeeded access to the underside of the engine.

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The basics of what's needed, propane torch and sparker, stainless steel brush (plain steel isn't any good apparently) a few small steel brushes, safety goggles, gloves (if i truely need them will depend on how good/bad i am at this, but i'll err on the side of caution for now), fire extinguisher (same again, i hope i don't cock up and set something on fire), the brazing rods & the screwed up peice of engine.

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Closeup of the rods.

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I used my crappy camera tonight, it's macro function is screwed up unfortunately. You can still kind of see the stripped thread in this picture

Next up, having a practice run and then fixing the stripped thread.

[mike-s]

Had my first go at doing this today and have come to the conclusion that i just cannot get sufficient heat into the metal with propane, am going to likely have to go and get a MAPP torch tomorrow. Annoying.

[the kid]

Had my first go at doing this today and have come to the conclusion that i just cannot get sufficient heat into the metal with propane, am going to likely have to go and get a MAPP torch tomorrow. Annoying.

Put it in the oven first

[mike-s]

Not happening, I'm not sure I'd be able to get it back down to the garage fast enough. Have had a bit of a read and it seems the default torch the propane comes with is suitable as it's a "pencil" torch whereas you need a hotter flame, apparently a "swirl" flame does that nicely and if it's got a larger flamefront (i.e. wider flame) it does an even better job. I previously bought one of these.

Tonight I went out by bunnings and got one of these, i nearly bought this but the bigger flame front on the torch i got was worth the extra $20.

Incidentally Bunnings DO stock aluminium soldering rods at $9.95 for two, i got a pack just in case so i could compare with the ones i got from the dude on ebay.

[Sulli]

Oxy acet will be the only way you will get enough heat into the casing to weld /solder. preheating is wise as it will help eliminate the warping effect as aluminum is prone to do any thing else is a waste of time imho
Oh by the way if the ally is magnesium based be prepared for a more difficult job but not impossible HTH

[mike-s]

I can't remember what the first set of rods are, but i know that the second set of rods i have are a magnesium zinc & copper alloy. Apparently the zinc bit is the key to getting the rods to bond with aluminium.

Fingers crossed there's not a warp problem, will do my best to make sure i even out the heat.

[aggerz]

Had my first go at doing this today and have come to the conclusion that i just cannot get sufficient heat into the metal with propane, am going to likely have to go and get a MAPP torch tomorrow. Annoying.

Exactly my problem too.. I had a crack at doing it on the weekend (same type of rods) no matter what I did just couldn't get anywhere near the right heat

[Rossi]

Many moons ago, we used to use old engine oil as "flux" to stop oxidisation when soldering Aluminium

Probably a lot cheaper to have bought a "helicoil" kit ?

http://cgi.ebay.com.au/HELICOIL-TYPE-TH ... 5d2a66758c

[budgienutz]

Very interesting,keep up the good work

[mike-s]

Ok, buying a MAPP torch was a brilliant move, despite the fact it cost me nearly as much to get it as a new sump pan would have cost, but i was in it for the adventure and "i can fix it" with a little bit of pride added for good measure.

My biggest problem was the fact that i was unable to get a threaded bolt of the right diameter (14mm x 1.25 pitch x 2cm+ long) so i would get a thread the entire way through. They just don't seem to make them. I could have gotten one custom made, but given the purpose, i'm sure that would have cost a rediculous sum of money to do.

I ended up gettin the knack of it, there are two heat levels. 1) hot enough to melt the rods, this means there is enough heat for the material to liquify, but not enough for it to really do much, a solid tap with a hammer can get the alloy to split from the parent metal.. 2) The second temperature is where the aluminium has enough residual heat to allow the metal to wick in and get a good hold, this is the point you want to get to for a solid bond.

Even though i got the temperature right, I had to do a bit of a dodgy fix due to the above mentioned bolt being a pain in the arse, and the fact that there is a lip with a little insert cut out on the inside of the bolthole which all the extra alloy proceeded to piss right out of and never pool sufficiently to make a full thread. But the end result is pretty acceptable with about 75% of the bolt getting a new thread. All i have to do now is try and get the last couple of mm of thread sorted so that i can put the bolt in and use it.

[tim]

Curiosity got the better of me and I had to check this out. Good going Mike, looking fwd to some pics Of the finished Product.

[mike-s]

And others were right about warpage, however i managed to minimise this to a tiny fraction of a millimeter (my estimate is probably about 0.1 or less warpage) by not just focussing the heat on where I wanted to fix it, but by making the whole thing sit above 250-300'C or so This can and will be compensated for by putting a slightly thicker paper gasket in between the sump and the oil pan. It's easy, i've got a whole roll of 1mm gasket paper sitting on a shelf.

[edit] See below post for moment of genius # 465[/edit]

[mike-s]

F'k sake I'm an idiot! I just remembered that 14-1.25 is a standard pitch for car spark plugs, i'll just go down to repco or something tomorrow and buy the shittiest plugs i can find with 14mm width and a long thread and voila! sufficient thread to do the repair.

[laidback]

F'k sake I'm an idiot! I just remembered that 14-1.25 is a standard pitch for car spark plugs, i'll just go down to repco or something tomorrow and buy the shittiest plugs i can find with 14mm width and a long thread and voila! sufficient thread to do the repair.

Simple solution eh...watching with interest.

[mike-s]

Got a spark plug from a Hilux, It's the right diameter & pitch and the threaded segment is nearly 3cm long!

Just what i need.