G-05 or Peak Global for Subaru?

[gavinl]

Recently I replaced my 1997 Subaru Impreza's radiator with a Koyo aluminum core/plastic tank type.

After back flushing with my garden hose I filled the cooling system with PEAK Global Antifreeze and distilled water. After a month there's seepage (saw yellow powder-like residue) along the clamping area between the core and plastic tanks. No significant drop of coolant level though, just that I have to clean off the area quite often.

Now I'm running Prestone's radiator cleaner with distilled water only, intending to flush with distilled water (e.g. remove thermostat, run engine, drain and fill......).

Question is should I stick to PEAK Global that meets Subaru's spec JASO M325 & JIS K2234 or Valvoline Zerex G-05 which does not have the Japanese specifications?

 

[Ray H]

The major Japanese players, Honda, Nissan, and Toyota, like high doses of phosphates in their coolants for the added aluminum corrosion protection it affords. Presumably Suburu is in lockstep. G-05 has no phosphates because most of the European players don't want phosphate precipitates forming due to Europe's crappy HARD water. (Like distilled water is unavailable in Europe?) Two entirely logical approaches, and yet, entirely at odds. As long as you're using distilled water to "cut" the antifreeze/coolant concentrate, I doubt that either brand you mentioned makes much difference in America - they're both good products. Since by now, your Suburu probably is no longer under warranty, I doubt you'll have to worry about a warranty claim problem, anyway, either. The leakage at the tank/radiator core seal means either the new radiator is defective, the pressure cap is over pressurizing the system, or both. On the chance that you're still running the original OEM cap (they do poop out eventually), try a replacement cap and specify one that it does not exceed the pressure rating of the original cap or as stated in your owner's manual.

 

[gavinl]

Thanks Ray, I'm just done with flushing out the cooling system, it's all clear distilled water in my scooby right now

Since japanese makers like phosphate in the antifreeze would it suffice if I get some regular green Zerex? Oh, and a replacement rad cap too

 

[Ray H]

Japanese OEMs do not like silicates - which regular green antifreeze is loaded with. The problem with silicates is that while they do an excellent job of protecting against metal corrosion while stable, they don't stay that way over time. (That's the reason most OEMs used to advise flushing and replacing the antifreeze/coolant every two years.) When silicates go goofy they may fall out as hard precipitates (not at all unlike sand - which is silica, and so is glass) or as a gell-like glop. The hard precipitates are nasty to water pump seals. The gell can sit in smaller coolant passages or the bottom of the radiator as a semi-clog. Traditional "Green-Snot-of-Death" is becoming increasingly difficult to find - and for good reason. Virtually all OEMs (with the possible exception of Hyundai*) no longer advise using it in current vehicles. While it worked well when radiators were brass and engines were cast iron, much or all of current engines is aluminum as are radiators and heater cores these days. By the way, if you're running straight distilled water in your Suburu at the moment, get something in that cooling system pronto - you're wide open to corrosion.

*My 2003 Sonata owner's manual merely advises the use of "a quality ethylene glycol antifreeze/coolant" - a model of non-specific "advice" in my opinion. The factory juice (dyed green) had turned a little murky in less than two years. Out it came. In went WalMart's SuperTech "universal" extended life antifreeze/coolant** and distilled water after 7 flushes with cheap WalMart distilled water. Car and owner both doing fine at six months and counting. There are no silicates or phosphates in this product - essentially a DEX-COOL without licensure from GM.

**I've reason to believe this stuff is actually made for WalMart by Prestone - same listed corrosion inhibitor ingredients, same alpha numeric production/date code configuration, and very similar wording describing how wonderful the stuff is on the back of the jug.