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Brazing the Koyorad

Joined
27 July 2007
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Location
Denver, CO
Question for the DIYers: My Koyorad sadly shipped with a pinhole leak on the upper tank:

20230820_114435.jpg

I have some brazing rod that will fix this permanently without the need to remove the radiator from the car. However, I need to make sure there is air behind the weld so that I can get the aluminum hot enough with the torch for the solder to melt. I REALLY don't want to drain the entire coolant system- I just need to lower the water level in the upper tank to about 10mm below the hole. If I open the rad bleeder and the rad drain only, my thought is that I would only put air into the rad since the coolant pipes are lower than the bleeder. Then, I could refill and bleed air at the rad bleeder and maybe the heater core bleeder. Thoughts?

@Kaz-kzukNA1 ?
 
I drained only the rad when I swapped in the new Masiv radiator the other day and was getting air out of all of the bleeders afterwards. You don't need to drain the system fully but you will need to go through the bleed process.

I did the bleed valves one at a time and used a short hose on them going into a cup just cycled through them twice to avoid a mess. It was pretty easy and quick.
 
From my hose replacement extravaganza last fall, my recollection is that the bleeder on the radiator (and the location of your pinhole) is lower than the expansion tank so the expansion tank will have to be emptied first. Otherwise it will slowly drain through the bleeder. I can't look at my car because it is in storage so I am also a little fuzzy as to whether the three big hoses at the rear firewall are level with or above the top rad tank. If they are I think they will also drain (very slowly) out the top bleeder in which case this is a bust.

If you have a couple of those big hose squeeze clamp things you can clamp off the upper and lower rad hoses. Then you should be able to drop the rad level through the rad drain enough to do your repair on the top tank. Unless you are quick like a bunny I expect you will need to remove the bleeder to allow venting during the repair because the heating will cause expansion of the interior air which will other wise vent through the repair area.

Personally, with that nice new Imola orange paint job I would not be attempting this repair with the rad in the car. With the big hoses clamped off you can completely drain the rad, and you may (caveat to follow) be able to remove and repair the rad and then do a pressure test to confirm the repair. The biggest impediment to this working out is that on my 2000 the lower rad hose is a short miserable little piece of rubber. I don't know whether you can squeeze the rubber elbow shut with the squeeze clamp and still manoeuvre the hose back on to the rad with the clamp in place. In a perfect world you would leave the lower squeeze clamp in place on the hose until you had the hose in place on the rad and then back fill the rad from the upper hose opening before removing the lower squeeze clamp.

Whether you do the repair in the car or remove and backfill the rad this will leave you with a small air volume trapped in the upper tank area and the slanted upper hose connection. With a full expansion tank hydrostatic pressure might eventually force the air out through the rad bleeder. However, I really think you would want to go through the heat up and cool down part of the bleed / burp cycle just to be sure. The amount of air to be bled should be minimal. I would want about 1 l of coolant from the heater hose bleeder with no bubbles before I was satisfied (I live in the world of failed head gasket paranoia). Kaz's method where you clamp a clear hose on to the heater pipe bleeder and then extend that down to a jug at ground level worked best for me.
 
Question for the DIYers: My Koyorad sadly shipped with a pinhole leak on the upper tank:

View attachment 186355

I have some brazing rod that will fix this permanently without the need to remove the radiator from the car. However, I need to make sure there is air behind the weld so that I can get the aluminum hot enough with the torch for the solder to melt. I REALLY don't want to drain the entire coolant system- I just need to lower the water level in the upper tank to about 10mm below the hole. If I open the rad bleeder and the rad drain only, my thought is that I would only put air into the rad since the coolant pipes are lower than the bleeder. Then, I could refill and bleed air at the rad bleeder and maybe the heater core bleeder. Thoughts?

@Kaz-kzukNA1 ?
apply vacuum at the expansion tank , coolant wont leak out ,only air will go in . you have to be very good with the heat and the filler rod. i would try a epoxy first and see if it holds . if it is a pinhole you could try purosity tablets , we put them in every car we built , and so does every other auto manufacture . otherwise pull the radiator ,best of luck
 
don't googl "brazers"o_O
 
Just discovered this:

https://www.mastercool.com/product/alum-bond/

It's such a tiny hole that the dried coolant actually is sealing it right now. I'm sure this stuff would be a permanent fix. I'm still leaning toward the brazing rod since it is a metal repair. But that epoxy looks real interesting. No torch needed...

Also, I ordered new coolant. I'm just going to do a normal drain and fill. Sigh.
 
Just discovered this:

https://www.mastercool.com/product/alum-bond/

It's such a tiny hole that the dried coolant actually is sealing it right now. I'm sure this stuff would be a permanent fix. I'm still leaning toward the brazing rod since it is a metal repair. But that epoxy looks real interesting. No torch needed...

Also, I ordered new coolant. I'm just going to do a normal drain and fill. Sigh.
Paul just remember "the devil you know", before you try re -tig or brazing or plugging it the epoxies on the market now are proven .
 
Epoxy is the way to go - as Ralph said it won't fail but if, in some parallel universe, it were to fail removing it and going to plan B is a lot easier than dealing with a torch job that goes south.
 
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