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I have a 93 Honda Accord EX with 130,000 miles on it. Recently, the top section (plastic) of the radiator blew out (put a 1x2 hole in it). The car was at idle and as far as I can determine, the car did not overheat. This weekend I replaced the radiator. The car seems to be running right. The upper radiator hose gets hot after a while, so I guess the thermostat is working correctly. However, the cooling fans are not running when the car is shut off. If I remember right, they usually ran after shutting off the car. The fans do work when the A/C is turned on. I was wondering, have you seen this problem before? Was this the result of an old plastic radiator blowing up, or is there something else that may have caused the radiator to blow?

The radiator “blowing out” the tank is very common on Honda's that have over 100,000 miles or 5 years on them. The radiators on these cars are pretty much restricted after this much time and mileage. What caused the “blow out” is called "steam erosion" this erosive action erodes away the plastic tank (which is made out of "Nylon 66" or a product that is very similar to "Nylon 66".) The reason the fans don't come on NOW when the car is shut off is due to the radiator getting rid of the excessive heat when it is running. The fans do come on when the car get hot enough and kick off when it "cools down” (I am assuming they do) The fans will come on when the car is off if excessive heat builds up in the radiator. (Sensors in the radiator detect this excessive heat build up.) This will happen with the key and engine off or on. What you thought was a normal condition was the car telling you for the last year or so that it has a problem! Please make sure that your Ph in the radiator stays at 8.0 or higher on this car. All cooling hoses should be changed as well after 5 years or 100,000 miles. Steam erosion destroys hoses from the inside out, just like your radiator tank was destroyed. Once all your hoses including heater hoses and clamps are changed have a shop "Exchange" your coolant. (This has to be done with a special machine) Flushing is something that shops are being taught "not to do" with today's composite radiators such as your Honda. City water and well water should never be added to antifreeze when getting a proper 50/50 mixture. Distilled water only should be mixed with antifreeze! If not, you are shooting yourself in the foot and not doing this job properly. If you do have to "flush" a cooling system due to scale and rust. The radiator should be out of the car while this procedure is being performed. Flushing a cooling system using this method of city water (or well water), forced under high pressure is opening a cooling system to a plethora of problems down the road. This is why the manufacturers recommend cooling system fluid exchanges ONLY! This removes and replaces 96 to 98% of the old coolant. If you are flushing using a water hose method and are re-filling your radiator back up, you are lucky to change around 45 to 50% of the old coolant! This will give you a false feeling of a job well done. Replace the radiator cap YEARLY when you exchange the fluid to avoid steam erosion. An inadequately pressurized system means lower coolant boiling points. Lowered boiling points make steam which may put you down on the side of the road sooner than you think.

 

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