Recently I noticed the temperature on my original ’46 truck would rise to half way between 180 and the lower edge of the red strip on the gauge when driving at a sustained 50 mph on the freeway in warmer weather.  (I have a 180 thermostat in it)

It never rose while idling at intersections etc, just higher speed driving.

Looking into the radiator I could see that stuff was starting to accumulate on top of the core and starting to block tubes.

So, I asked the owner of a radiator shop I trust what I should put in to clean up the cooling system.

When he saw the original radiator, he emphatically said “Nothing, except water and air, never put a cleaner in an old radiator.”

I of course asked “air?”

I was skeptical, but he insisted there needed to be air.

So I removed the lower radiator hose from the water pump, and I found a hose that would fit inside the lower hose and over top of the valve on our garden hose.

I punched a hole in the side of the hose a little smaller than my air chuck and stuck it in.

With the upper radiator hose off the thermostat housing and the cap removed, I turned on the garden hose.

Stuff was coming out… but when I gradually opened up the air to wide open, the water in the radiator went into what looked like a full rolling boil and TONS of stuff came out.

After the water ran clean, I looked in at the top of the core and it was nice and clean.

I put the hoses back on, refilled, and all is well.

And no leaks

It worked so well I thought I should share it here.