Please Help Diagnose 53 Roadmaster Overheating

Hello All,

I got a 1953 Buick Roadmaster 2 years ago - good running condition, but needing a bit of restorative maintenance. I had it checked out by a professional mechanic, gone over for issues that I might not know to check, etc.

The exhaust had a few small leaks which I got fixed. Timing and carburetor balancing/tuning were done. Leaky valve cover gaskets replaced, etc.

It ran more or less fine for about 6 mo, then began to start overheating. I had the mech. check that too. So far we have replaced the thermostat, checked the coolant system pressure, and re-tuned the carbs but nothing has helped. He wanted about $500 for a new radiator, which is more than I had budgeted at the time.

I took the car home pulled the radiator out to inspect it, and check the system for other possible issues like a loose fan belt, bad connections or corroded coolant lines, etc.

The radiator seems to be relatively clear - I get as much fluid flowing out one end as I put in the other. The belts were tight, and the coolant lines seem fine. The flush pulled out some gunk, but it wasn't too bad.

In researching this I'm finding that the coolant channels in the block may be the culprit and I should pull the freeze plugs and clear out the block channels.

How can I confirm this before I go into the block?

I recommend pulling the radiator and taking it to a reputable radiator shop and have it flow tested. They can then tell you if you have a restriction. I like to do the easiest jobs first. Removing soft plugs probably involves removing exhaust manifolds which could lead to broken bolts and bad things.

I would keep looking for an external problem. You would need a ton of sediment in the block to cause over heating. Check for loose water pump impeller, corroded fins on the impeller, bottom hose sucking shut, late timing, etc. You didn't say how hot it was getting or under what conditions. As someone that has been visiting this forum for a few years I've learned not to assume anything. Overheating can mean anything from, "It reads a little higher on the gauge than I think it should", to "Holy cow, we melted some solder out of the radiator when we seized it!". Tell us a little more about what it's doing.

By overheating I mean that after about 20-30 minutes of idling, or 15-20 minutes of "normal" (not pushing it hard from a stop, mostly flat, with idling at a few lights) driving it's temp indicator is all they way up to the "Hot" indicator, and the fluid in the radiator is boiling out the overflow tube.

I was also thinking water-pump. I can have the radiator tested as well.

I began pulling things apart to get at the radiator and pump last night. I see that there are hoses running from my water pump back behind my block connecting I presume, to the transmission.

Does the Dynaflow transmission have it's own, or any cooling? Does it share the engine's radiator system?

you will still need to pull the block plugs to eliminate the crud factor. I used a 1/4 in. piece of copper tubing that I adapted to my garden hose spray nozzle.In mine I poked and squirted and bent all around in the water jackets and was amazed at the amount of crud i got out. there were pieces of rust that had peeled off the cylinders that was in there for years. Could get more out if the engine was out and upside down.

Yes, they run coolant back to the Dynaflow for cooling. There should be a little heat exchanger bolted to the side of the tranny.