What could be causing this Vanagon to run hot?

Dear Car Talk

Dear Car Talk | Apr 01, 1997

Dear Tom and Ray:

My son in Florida has been having overheating problems with his '85 VW
Vanagon. On a trip to visit us recently, one of his lower coolant hoses
blew. While he was here, one on the upper right side blew. On his way back
home, the upper left side blew. He says up to about 60 mph, his temperature
gauge reads normal. But when he goes over 60 mph, it immediately goes up.
He took it to a dealer, who replaced one more hose and the radiator cap,
but the temperature gauge still reads hot. Any thoughts? -- Len

RAY: My first thought is, boy, am I glad I don't drive around in a VW

TOM: No, he means thoughts about what's wrong with his son's car, you
knucklehead. Len, I think your boy has a plugged-up radiator. That's what's
causing the overheating at high speed and the buildup of excess pressure in
the cooling system, which is causing those old hoses to blow.

RAY: If it's not a plugged-up radiator, it could be a blown head gasket.
That would allow hot combustion gasses to get into the coolant, and that
could also be responsible for the excess pressure and temperature.

TOM: I'd check for the bad head gasket first. Just have your mechanic
remove the radiator cap and hold his emissions wand over the opening. If
the emissions tester detects excessive hydrocarbons (i.e., more than 50
parts per million) in the coolant, then the head gasket (or the head) needs
to be replaced.

RAY: If there's no sign of combustion gasses in the coolant, then I'd have
the radiator removed and flow tested. And if it tests poorly, as I suspect
it will, he'll have to put in a new one. And then this Vanagon will be as
good as new -- which wasn't that good, but what do you want from us? We're
just mechanics, Len, not miracle workers.

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