Crossflow Radiator failure

This one goes back a few years, but the problem still comes up occasionally...

I had a failure of a GM Olds 88 cross-flow radiator--some of the top tubes pulled out of the tank on one end--so I took it to the radiator shop, naturally. The owner mentioned that he was glad GM made that model, because it surely carried him through some lean times, what with running with air in the tubes. I got to thinking about that after I had another failure, and here's what I figured out:

The cooling system gets air into it and creates a temperature difference between the top tubes with the air, and the bottom tubes with coolant in them. This in turn makes an expansion difference which eventually pulls the tubes out of their solder joints. NOW..."Where does the air come from", you ask. The coolant-recovery tank is there to eliminate that problem, right???. OH, but it IS supposed to!

GM, in all its corporate eagerness to cut to the lowest cost on everything, makes (or outsources from Timbuktu or Elbonia) the coolant-recovery tank with a blow-mold with its halves which almost line up. (If they lined up and were properly maintained, it would cost more to assure quality.) The result is a small ridge on the inlet line where the tube to the radiator clamps on. This ridge allows air to be drawn in.

Since you read the owner's manual, you dutifully fill the tank with 50/50 mix and the level stays where you left it. Or, and you won't notice this, it overflows--but while you're driving. What happens is the coolant heats up and expands into the tank, as it should. When it cools down, though, instead of slowly pulling coolant back into the radiator, it pulls air by the little ridge under the hose clamp, because that route has slightly less resistance to air flow than pulling coolant the few inches from out of the tank.

So your tank level remains constant (or, as most diligent operators only note, it has coolant in it...), while the radiator has increasing air in it. The result is eventually that described above: tube pullout and a trip to the garage or to the dealer, where they will cheerfully sell you a new radiator, installed, for many hundreds of $$$, when the problem is original design.

I have never seen a maintenance alert on this. In most cases it won't happen until the warranty is expired, so manufacturer attention to the problem is, let's say, spotty...

Hope this helps some of you out there! I'll send some more of these insights as I get time...

For now, let's curse side-post batteries (Delco in particular) for their sorry little green/red window and impossibility for jump-starting, and for acid leaks by the terminals where they pass through the plastic--corroding and doing weird things to operation.

///Charlie Jones...

PS to Bob Hewitt--Keep up the good work. I like your website. If I can add anything from a Mechanical Engineer/Failure Analysis expert's perspective, I'd be happy to, at JONESCF@AOL.COM..

Message me at BobHewitt@Misterfixit.com

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