Refugee18
I have a 45kw (Ford 4.2l v-6) model 5421 with 170 hours since new in 2007. The welds on the radiator are leaking. Generac’s build sheet shows a US made radiator, however, last time I checked no US made radiators had a plate below the fill cap saying “MADE IN RUSSIA”.   I would like to replace this radiator with an aluminum one.  Has anyone found a match with CSF or another quality manufacturer? I am concerned about matching up the fitting for the low coolant sensor and would also like to avoid having new inlet and outlet hoses made if the locations don’t match.  Plan B would be to remove the current radiator and have the tanks and core replaced. Any input would be appreciated.
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Cobranut
Repair is a viable option, however, there are several radiator manufacturers out there who may have something that could be adapted to your application, or can custom fab what you need.
Here's one I have bookmarked, in case I need something.
https://www.championcooling.com/

Not sure aluminum is the best option for long life though.  They're usually chosen for light weight and high thermal efficiency, but most genset radiators are huge in relation to engine output, and I suspect copper/bronze is more corrosion resistant.
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Refugee18
Thank you for the response and the link to Champion.  Have you used a shop to repair/redo the tanks and core on one of these Russian radiators? I try not to reinvent the wheel, if possible. Champion looks to be all aluminum so not sure they would do copper or bronze work. 
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78buckshot
The leaking Russian radiators is the norm. I have not researched a replacement from any other source.
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Peddler
In the past I have taken these radiators to a local guy and had them re-cored.  It is cheaper than an OEM replacement from generac and with a quality core it will be 50% heavier than the original.  If just the neck is leaking you can have a new neck soldered on with an american style radiator cap.
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78buckshot
If it were mine I would do as Peddler has done, have a local radiator shop re-core it. Nothing beats the longevity of the heavy copper/brass, my 1957 Chevy truck has the original Harrison radiator and no leaks.
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Birken Vogt
Another vote here, copper/brass is generally superior to aluminum as a radiator material and if you have yours rebuilt, the shop can hopefully find all the weak points and correct them into something better than original.
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