Another Heater Core Thread

josephbelttj said:
I’m actually on the fence about brassworks because of the copper construction. Old vehicles used copper radiators and components, but modern vehicles use aluminum. Using a copper heater core with an aluminum radiator makes a battery and causes corrosion. Sure, modern coolants have additives to prevent electrolysis, but those same ingredients aren’t great for soft metals (e.g. copper or the leaded solder holding it together).

An aluminum heater core in a vehicle with an aluminum radiator without other copper components seems to make the most sense.
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Generally true, but aluminum already is and will remain the least noble metal in the system. Copper is farther down the galvanic series than iron is, true, but the radiator has much more area to distribute the corrosion. The general rule for mixing copper and aluminum is that you want the ratio kf aluminum to copper surface to be as high as you can reasonably achieve, certainly at least 1:1, so while it could be better, it's far better than using an aluminum heater core with a copper radiator.

There also needs to be an electrical pathway to facilitate the exchange of ions (the "battery" doesn't drain unless there's a completed circuit) and the radiator core is insulated from the brackets and therefore the chassis by plastic tanks. I know the HVAC box is mostly plastic so the heater core may be insulated as well but I haven't had mine apart yet.

The comment about modern coolant chemistry may be true, I had to do some research but I did find some references stating that OAT was not good for soldered copper heat exchangers.

One example

https://e9coupe.com/forum/threads/c...m30-aluminium-head-engines.43737/#post-385398
IAT
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(Inorganic Additive Technology) - old technology not suitable for aluminum but good for copper based (soldered) - should be exchanged every 2 years
OAT (Organic Acid Technology) - can dissolve solder, so it is not suitable for copper - 5 years lifetime
HOAT lub SiOAT - new version combining IAT (silicon) and OAT (organic acids) - pushing out IAT fluids
NMOAT - for industry machines. Typically universal and compatible with most of materials used in heating/cooling installations. 7 years of lifetime
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IAT is old school green, which is kinda funny that they say it's not suitable for aluminum since the first half of TJ production came with aluminum radiators and IAT coolant.

Zerex g05 and what came in TJs starting mid-run is HOAT.

Definitely sounds like we want to avoid OAT but I don't think the TJ ever got that from the factory so not sure if anybody is using it.
 
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freedom_in_4low said:
Generally true, but aluminum already is and will remain the least noble metal in the system. Copper is farther down the galvanic series than iron is, true, but the radiator has much more area to distribute the corrosion. The general rule for mixing copper and aluminum is that you want the ratio kf aluminum to copper surface to be as high as you can reasonably achieve, certainly at least 1:1, so while it could be better, it's far better than using an aluminum heater core with a copper radiator.

There also needs to be an electrical pathway to facilitate the exchange of ions (the "battery" doesn't drain unless there's a completed circuit) and the radiator core is insulated from the brackets and therefore the chassis by plastic tanks. I know the HVAC box is mostly plastic so the heater core may be insulated as well but I haven't had mine apart yet.

The comment about modern coolant chemistry may be true, I had to do some research but I did find some references stating that OAT was not good for soldered copper heat exchangers.

One example

https://e9coupe.com/forum/threads/c...m30-aluminium-head-engines.43737/#post-385398


IAT is old school green, which is kinda funny that they say it's not suitable for aluminum since the first half of TJ production came with aluminum radiators and IAT coolant.

Zerex g05 and what came in TJs starting mid-run is HOAT.

Definitely sounds like we want to avoid OAT but I don't think the TJ ever got that from the factory so not sure if anybody is using it.
Click to expand...

If my experience today is any indication, the plastic tank will go before the aluminum core. I guess I can’t complain about a 21 year old plastic tank on the radiator giving up the ghost, but if I can get that kind of service life out of a replacement heater core and radiator, I’m not sure there’s a compelling reason to avoid aluminum and plastic construction.
 
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josephbelttj said:
If my experience today is any indication, the plastic tank will go before the aluminum core. I guess I can’t complain about a 21 year old plastic tank on the radiator giving up the ghost, but if I can get that kind of service life out of a replacement heater core and radiator, I’m not sure there’s a compelling reason to avoid aluminum and plastic construction.
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The tanks do seem to be the most common failure mode. That ends up convincing many that they need an all aluminum radiator, which if my theory holds water (punny haha) that would close the circuit with the engine block and may play into why those develop pinhole leaks within just a couple of years.
 
It’s not a coincidence. Both my heater core and radiator only began leaking after having to remove and reinstall the radiator and hoses because of that stupid body lift. Plastic gets brittle with age and heat cycles, and they’re both 20 years old with 150k miles, so I’m not at all surprised after being tugged on and jostled around.

The take-away is that the aluminum cores held up fine, but I doubt anyone can build an affordable full aluminum radiator. If the plastic/aluminum version can hold up to two decades of use, the cost/benefit of chasing something better isn’t there. All the major automakers figured that out.
 
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