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Old 14 Feb 2008
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Can you weld on a F650 radiator while it has coolant inside?

Hey guys, I am guessing that the answer is probably no. I am looking for a way to repair my radiator which had a whole at the top of the blades which I had fixed at a radiator shop in Ecuador, but is now starting to leak again in Bolivia. I have not taken the radiator out before and am not sure I want to risk messing something up in Bolivia.

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Old 14 Feb 2008
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short answer: NO

Long answer: Not a chance, unless you want a face full of steam, no weld etc etc etc etc etc.....

Dismantle is the only way to go, unless you use Rad-seal or similar....... or dare I suggest this on here? The WHITE ( Albumen) of an egg ( yep, the things laid by chickens!) or in the case of a bike, half of an egg white, as a temporary measure, dropped into a COLD engine's radiator and then started up and ran.
the idea is the egg gets hard and chopped up, and as it leaks, little bits of fineley chopped egg white eventually 'Dam' the leak.
as I say, its an EMERGENCY measure, and would need a damn good back flush after....... might get you outta trouble though.
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Old 14 Feb 2008
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I wouldn't risk it. I don't own a F650 but I think the radiators work in the same way cross-manufacturer!

Whether using rad-weld or similar or actually welding you normally want the surfaces to be as clean as possible. The effort of prepping it will be a lot less than having to redo a failed repair!

Good luck
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Old 14 Feb 2008
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If you take the rad off, it's drained anyway? (I guess you are contemplating welding insitu) - anyway, check with the welder!

Water will conduct heat away which is not a great idea while welding and/or, it will boil-off locally to the weld heat which is also undesirable.
(Beware of super-heated steam; steam under pressure - it hurts!).
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Old 14 Feb 2008
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I have not worked on a F650 Radiator.

You will need to take it off and drain to make a good repair. Rads are normally brass cores and headers and sometimes plastic headers. The cores are normally soldered not welded. If it is the core that is leaking because the fan has hit it and you can see the hole you could try to squeeze the pipe together with some pliers, if it a big hole you could cut the pipe at the hole, flatten it and fold it back on it self (may still need solder). This can be done without taking the fluid out or removing the rad. This method will reduce the flow in the rad fractionally but I don't think it will make a difference.

Ask around the car and truck repair yards as radiator repairs are often done by a specialist it will mean taking it off but they will be able to test the repair with compressed air in a water tank. Test pressure will be a little more than the radiator cap I guesstimate 10 psi max.

I hope this helps.

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Old 14 Feb 2008
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If you're welding in situ be very careful of the electics. At the very least disconnect the earth (-ve) lead. I think you'll find that the core may be alu anyway so I'd be very careful. On the plus side wherever you are in the world you won't be far from someone who can do a better repair than you. I've had a lot of success with liquid rad repair solutions in the past.
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Old 14 Feb 2008
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Short answer...don't weld the rad on the bike! Take it off and do it properly. It shouldn't be hard to find a rad shop specializing in these repairs. People in the third world can't afford new parts and laybor is dirt cheap, hence anything can be repaired.
It's okay to weld things on the bike, i do it all the time. I built my entire rack on the bike without disconnecting the ground. The key is positioning the ground properly so no current loops through fragile computers and such. Even with the ground disconected you risk having a ground loop through fragile parts. That being said, you will not preform a good dependable repair while the rad is on the bike. It has to be drained, dry and the repair location absolutely clean with a wire brush and acid fluxed before soldering.
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