Can radiator be tested ahead of big blast?

Dear Tom and Ray: I drive a 1994 Toyota Celica with 111,000 miles on it. About six months ago, I had the radiator replaced, because it was cracked and leaking. Today it exploded! I took it back to the same mechanic who installed it, because it was under warranty. The mechanic told me that he has never seen a defective radiator in all of his vast (six years) experience. He stated that the most probable cause was that my motor was bad and caused too much pressure to build up in the radiator, causing the massive and totally unforeseen explosion. He told me that if it is indeed the engine, if he puts in a new radiator it will just explode again in a couple of days. He also said there is no way to test this faulty-engine theory other than waiting to see if the new radiator explodes. I'm not too excited about this idea. Does a bad engine really cause a radiator to explode, and is there any other way to test this theory?

Laura

Ray: Well, your mechanic is right that something is indeed wrong with your engine, and that it would be unwise to just replace the radiator.

Tom: But there IS a way to test it other than just driving around and waiting for the new radiator to explode.

Ray: I suspect you have a bad head gasket, Laura. You say that you replaced the radiator about six months ago ... my guess is that before you got around to replacing that radiator, the engine overheated -- maybe several times. And that's what caused your head gasket to fail.

Tom: What's happening now is that pressurized exhaust gases are leaking out of the cylinders and getting past the broken head gasket into the engine's cooling passages. That's building up tremendous pressure in the cooling system -- a lot of pressure. Usually when this happens, we see a cooling hose burst off before the radiator explodes, but I guess your hoses were on there pretty tightly.

Ray: Your mechanic needs to put a new radiator in the car -- at least to do the testing. You can't do a head-gasket test unless you get the engine up to operating temperature, and you can't do that without a working radiator.

Tom: Once the radiator is in there and the engine is warmed up, he can take his emissions-testing wand and hold it over the radiator opening. If we're right, the hydrocarbon reading should go bonkers, because you've got exhaust gases pouring into the cooling system.

Ray: Then you can decide if you want to spend $1,000 on a head gasket for this car -- plus the cost of a new radiator. I know you have a radiator warranty, but the radiator company will argue -- fairly -- that this wasn't the radiator's fault. So unless you bought the optional Radiator Explosion Rider, add a radiator to the bill, too, Laura. And good luck.