View Full Version : How to solder a radiator fin.

18th June 2012, 10:17 PM
Yesterday I sprang a leak in my GU 4.2TD radiator, luckily I was at home when I noticed it. I pulled the radiator out which was a very easy task. Slip the clamps off the hoses and pull the hoses off. Undo the nuts on the two top brackets. Pull off the overflow hose and then lift the radiator straight out with the plastic shroud attached. I found that the moulded part of the plastic shroud that sits against the radiator had worn through one of the fins.

I didn't get a photo of the damage but this is the part of the shroud that did the damage.


I got on the internet to see how I could fix the hole as I was sure that it could be soldered. There are a lot of different opinions and methods from tempory fixes using pepper, egg whites, tobacco and other strange substances to permanent fixes using epoxy, welding and soldering.

One site said that you could use plumbers solder and flux to repair the hole after getting the area very clean with a wire brush and emery paper. I tried this method but couldn't get the solder to stick to the aluminium.

More research and I find that aluminium is extremely dificult to solder as it oxidises in air as soon as it is exposed. I read alot of technical discussions that did my head in before I came across some utube clips showing an aluminium rod called alumaloy. You have probably all seen it too, a bloke punches a hole in the bottom of an aluminium can and then solders it up and the soldered part is 10 times stronger than the original aluminium. These rods also go by the name of Durafix but seem to be more popular in America than Australia.

After further research I found that you can buy the same rods at Bunnings but they go by the name of Bernzomatic Aluminium Brazing and welding Rods.


They are not cheap and cost $10 for 2 rods but they work. No flux is needed the aluminium has to be cleaned with a stainless steal wire brush and you heat the aluminuim first then scrape the rod across the aluminium which apparently breaks through the oxide so that it can bond. This actually works and I was able to fix the hole.

Here is a photo of the repair. I melted some of the fine cooling fins when I was trying to use the plumbers solder because I was using a MAPP gas torch which is much hotter than straight lpg which is all you need.


18th June 2012, 10:31 PM
have you presure tested it ? will be awsome if its worked ill be buying a few for the tool box thats for sure

18th June 2012, 10:38 PM
They are a great product, I got 6 for $20 at the camping show, the demo was awesome with all sorts of things welded up. You did a good job there, hope it holds out.

18th June 2012, 11:14 PM
I fitted it back up and filled it with water. So far so good. I'll run it with water for a few days to make sure before I use coolant.


19th June 2012, 09:32 AM
Heres another name for them as well techni2000


19th June 2012, 09:50 AM
10 rods for $25 is a much better deal than Bunnings. I was sure that I had seen them somewhere for a good price but when I needed them in a hurry the Bunnings ones had to do.