So the rad in my 71 Roadrunner developed a leak somewhere in the bottom. I took it to get pressure tested and it didn't leak. They could see where it was leaking based on marks. It might leak when it heats up. I'm getting a recore anyway, man did the price of that go up.
I'm asking what antifreeze everyone is using today in their older cars. Should I stick to green Prestone? Can I use the more modern without having to change anything over?
It seems the modern antifreeze lasts a lot longer.

Before you send the the radiator out, drain the system, block drain plugs & all. Then try this with fresh water (not from a water softener system with salt in it)

www.evapo-rust.com/thermocure-cooling-system-radiator-rust-remover/

This way the system is clean before the re-cored radiator goes in.

i would stay with the normal AF. years back a lot switched to Dex cool and found it created some problems.

I'm getting ready to do a maintenance flush and refill.

I'm interested also; Green Prestone or is there something better in the old school stuff?

I use 50/50 Peak anti-freeze in my 69 440 motor. I buy it at the Dollar General store. Saves me a couple of dollars a jug.

Water cools better than anti-freeze, so unless you need protection against freezing, 25-30% anti-freeze is fine.
Did that on my Dually, along with a little lower temp thermostat, and brought coolant temp down a good 10 degrees.
On the older stuff, the green anti-freeze is fine.

You also need protection against RUST. Ask the boat owners about cast iron block and steel component coolant system rust. My original Sea Ray boat motor (5.0L) needed to be replaced and tried to get a local engine builder to try and save it which he said at the time he couldn't get to it for a many weeks. I said then I'll just find a remanufactured boat engine and that's when he warned me about boat motors don't use anti-freeze or coolant and there's no telling how thin a cast iron boat engine block might be on rebuilt/remanufactured boat engines. So off to Summit and bought a NEW 5.7L crate motor, changed the freeze plugs to brass, a new Melling cam that fit the boat motor rpm characteristics and a marine fuel pump. Picked up 65 hp and a brand new cast-iron block and cast-iron heads. Yes water cools better but it will also cause rust that could be an issue in the radiator, water pump, thermostat, etc., Just saying.

So my radiator will be picked up on Monday.
I'm sure there is some older antifreeze still in the block.
Should I just hook it up and fill it with new stuff and call it a day.
If I do this, I plan on dumping it and starting fresh next year.

i would hose the block out while everything is apart.
but that's just me.

^^^ That, and "run" the heater to flush all that out as well.
No better time to clean out the system.

X3

So a hose will do all that from the top?
I'll make sure the heater is on when I do that.

It will definitely help. Ideally one should pull the block drain plugs but they can be cantankerous ( ) Pulling the T/stat is less effective but better than not. Would've been best to do before having the radiator done .
If you do hose it, i'd follow up with a distilled water flush (2 or 3 gallons) to get rid of the crap in the city water.

The ethylene glycol never wears out unless it's been excessively overheated. Power plants in northern climates typically use an ethylene glycol heat transfer fluid for air preheating that never gets changed. All that is done is that the corrosion inhibitor is checked and replenished. As to automotive anti-freeze, with the current cost of the stuff, I'll drain it, filter it, throw in a bottle of corrosion inhibitor and put it back in.

I had a 440 Challenger radiator re cored in April 1990. I was making $6.60 per hour. Cost $220. I can only imagine what it costs now. Probably tripled or more.

Yes on the or more.

So I'll rinse it and fill it including a rust inhibitor?
Or should that be a separate step?
I'm picking up the Rad today.
Thanks