G-05 Anti -freeze Alum Rad. Question

[Mark Evans]

If I want to put Zerex G-05 Anti -Freeze in my 67 C-2 aluminum radiator, do I have to drain the entire system.As recommended in the archives. I now have a green type in the car.

If I do have to drain the block, how many block drains are there in a small block?

[Roy B.]

Re: G-05 Anti -freeze Alum Rad. Question

I would drain the system and two on the engine one on each side

[Duke W.]

Re: G-05 Anti -freeze Alum Rad. Question

I don't think it's absolutely necessary as is the case if you switch to an OAT blend, but I think it's a good idea.

The system is easy to "static cold flush" by removing the heater core supply hose on the inlet manifold. Then rig up some fittings to attach a garden hose to the inlet nipple, which will reverse flush the heads and block. Leave the block and radiator drains open as you do this, and also flush the heater core and expansion tank circuits. Since flush water may not reach the top of the radiator, it's also a good idea to remove the upper radiator hose at the themostat outlet and flush the radiator as the final step.

Once this "static cold flush" is completed you can "hot flush" the system by filling it with water and starting the engine and letting it run until the thermostat is open for a few minutes. You can do this mutilple times if you like, but let the engine cool for at least an hour before you refill it with cold water.

I don't recommend any commercial "raditator flush" products - just potable water. If your radiator and heater cores tubes are clogged from years of silicate and other salts precipitating out, I don't think any "radiator flush" product is going to put much of a dent in them.

For subsequent changes with G-05, just thoroughly drain the system by opening up the block and radiator drains. No real need to flush unless you suspect than the system has been contaminated.

Duke

[James W.]

Re: G-05 Anti -freeze Alum Rad. Question

Duke,

Is the G-05 anti-freeze recommeded because it does not contain phosphates as the label indicates? Is it still acceptable to change the coolant and use the currently available "green" coolant such as the Peak or Prestone brands? What are your thoughts?

Thanks,

James West

[Duke W.]

Re: G-05 Anti -freeze Alum Rad. Question

Modern OATs like Dexcool may not provide the best protection for solder joints, so it's not the best choice for vintage cars that have brass rediator of heater cores. Because G-05 is a hybrid it has both organic and traditional inorganic inhibitors.

Green provides good corrosion protection, but the heavy dose of inorganic salts, particularly silicates tend to precipitate out and clog tubes over time, which is why a HOAT is better for vintage cars - excellent corrosion protection including solder with less tendency to clog up tubes.

G-05 is a HOAT forulation that has been used in Mercedes-Benz cars for about 25 years. It is now used by DC and Ford for all their cars.

If you go to the Valvoline web site you will find five or six different antifreeze formulations (all ethylene glycol based, but differing in their corrosion inhibitor technology) to meet all the OE specs. I think traditional greeen is still available, but no OE currently uses it for factory fill. It's obsolete. This site also has some links to good technical articles on modern antifreeze technology if anyone wants to take a deeper dive.

Duke