coolant and cap for new aluminum radiator for a 1936 Dodge 1/2 ton panel

[36humpback]

I'm considering getting a new aluminum radiator for my panel.  My questions are: What would be a good coolant that is not real expensive? The coolant cap on the old radiator was a zero pressure cap.  Would I need to get a pressure cap or will a zero pressure cap work?  Thanks in advance.

[Rusty_OToole]

The zero cap will work but I would consider a 4 pound cap. I would not go higher out of concern for the heater core and water pump seal.

[Rusty_OToole]

Water is a good coolant, and cheap. But I would not use it without a rust inhibitor to prevent corrosion, and then only if I lived where it never freezes.

Ordinary antifreeze is likely your best bet.  Get a good brand name like Prestone, I would not try to save a couple of bucks on antifreeze when it might cost you a radiator or motor for big $$$$$ bucks.

[36humpback]

Thank you Rusty_Otoole. Very helpful info.  The coolant I was talking about was something like engine ice (expensive).

[Rusty_OToole]

Jay Leno swears by Evans coolant

 

 

[mfrank]

I actually make aluminum radiators, but not for this particular car. I always recommend a 50/50 mix. These days, there are dozens of very specific formuations, and for the combination of an aluminum radiator and iron block, I prefer Zerex G05, which is worth looking for. Water is better if you like rust and corrosion. I'm not a fan of waterless coolants. The primary consideration for the radiator cap is the thermostat. If you're using a classic bellows thermostat, they you are limited to at MOST a 4 lb cap. The reason is that the bellows is charged with alcohol. The bellows expands when the alcohol vaporizes, and this is dependent on both temperature and pressure. If you increase the pressure, you can actually cause the thermostat to close. If there was a wax thermostat available for your application, then you could probably go to a 7lb cap, but there may be other limitations in the system. So safest to go with a  zero or 4lb cap.

 

Another important point that your radiator should NOT be grounded. This may be contrary to advice you'll hear elsewhere, but there's a right way and wrong way to do everything, and sometimes "generally accepted knowledge" is the wrong way. The reason is that coolant will become conductive sooner or later. If you have a bad engine ground, your generator can ground through the coolant to the radiator if the radiator is solidly mounted to the chassis. This can be like running a plasma cutter over your expensive radiator. It may take some effort to suss out some appropriate rubber bushings to isolate the radiator, but it is important. And at the same time, you should make sure your engine grounding strap is in place and clean.

 

 

[Rusty_OToole]

Does your car have a heater? I might use a very light pressure cap like 4 pounds but never more than 7 for fear of blowing the heater or water pump seal. I do like some kind of pressure cap and a coolant recovery jug.