[Mart]

I'll tell this story - just in case it helps anyone at all.

I had a 57 Buick. I got it running from a non running condition (transmission rebuild). The first long journey I went on, after about 50 miles, it started overheating. I had to abandon plans to go to the show we were en route to, and try and get home. We were able to get home by stopping at every service area and hosing the radiator down with cold water.

Now when you hose it down, what you will notice is that some areas of the radiator dry off quite quickly. Others stay wet longer and some stay wet and never dry. You will observe vertical stripes of wet and dry patches.

The dry stripes coincide with the parts of the radiator that are not blocked. The wet parts show where it is blocked and not transferring any heat into the external water.

I removed the bottom tank and rodded out the tubes. Once back together it behaved perfectly.

So if you think you have a partially blocked rad, try hosing it down and see if it gives you any clues.

Mart.