I've read that the newer OAT (and HOAT too?) coolants are not good for older vehicles with lead soldered brass radiators and heater cores.
Why is this? Does the mix fail to adequately protect or is there something about it that actually attacks the solder? Is it just a problem with the soldered joints or does it cause issues with the brass itself?
I've got an older Toyota truck with a brass radiator and heater core and it calls for Toyota "red" coolant, which actually seems like a HOAT (phosphate and sodium benzoate). Toyota "pink" is also a HOAT (not sure how it's any different from 'red' other than the color), as is Zerex Asian (also phosphate and sodium benzoate), which I'm considering using.
What's the deal? What can I safely put in a system with lead solder and why?
Why is this? Does the mix fail to adequately protect or is there something about it that actually attacks the solder? Is it just a problem with the soldered joints or does it cause issues with the brass itself?
I've got an older Toyota truck with a brass radiator and heater core and it calls for Toyota "red" coolant, which actually seems like a HOAT (phosphate and sodium benzoate). Toyota "pink" is also a HOAT (not sure how it's any different from 'red' other than the color), as is Zerex Asian (also phosphate and sodium benzoate), which I'm considering using.
What's the deal? What can I safely put in a system with lead solder and why?
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