1990 Nissan pickup
Looking first at the engine bay to note the probable cause for the overheating, I thought maybe the water pump was no longer doing it's job circulating the coolant. However, there were NO signs of external leakage (typically a bad water pump will show signs of leakage). A failed water pump is a major cause of engine overheating, and an overheated engine usually causes the head gasket to fail. In this case, however, there were no signs of an external leak. The coolant (mostly water) just wasn’t circulating through the cooling system. It just sat there and boiled.
So, how did I know the water pump was bad without all the fancy testing equipment? Simple, all I did was feel the top radiator hose. A water pump that is not circulating will make the top radiator hose very hot, and the bottom radiator hose will be very cool. This was the case with the pickup. The core of the radiator should have been fairly hot, but it felt like it was only 65 to 100 degrees, depending on where I felt it. It appeared there was no circulation. A stuck thermostat will also cause these symptoms, so in this case, I pulled out the thermostat to eliminate it as a suspect. Still, no circulation.
Ruling the thermostat out, the next suspected failed part could be the water pump, so I pulled the water pump. Sure enough, NO IMPELLERS (the blades that move the water through the cooling system). The blades had completely dissolved, leaving just a spinning nub. This typically happens when the owner neglects to change the coolant every 25,000 to 50,000 miles. The coolant becomes acidic, and can quickly eat up the water pump impellers. (Another good reason to check the cooling components before using a sealer, but I’ll explain how that all works at a later time.)
At any rate, this was one of many of the cars I have worked on that needed a water pump, and after installing one, I was able to repair the blown head gasket with HGR-12. The owner happily saved over $2,000.00 and is now back on the road.
Quick Tip: If you have your engine oil changed every 6,000 miles, why not have your coolant changed every 6th time you have the oil changed. It's easy to remember that way, and you'll save a bundle, not to mention saving the time and frustration with a breakdown.
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