Engine Maintenance

How to Tell If You Need an Engine Flush


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Regular maintenance, including a thorough engine flush, also known as a cooling system flush, is essential to ensuring your engine keeps running strong for many years. Many auto makers and even makers of coolant and antifreeze products claim their products will last up to one hundred thousand miles. The problem with this is that they still quote a 12-15,000 mile change and flush interval. The following paragraphs will give some information as to why you want to perform regular engine flushing, how the process works and how to tell if you need one, excluding mileage intervals quoted in service manuals.

Why You Should Flush

Over time coolant and antifreeze products deteriorate under usage. Over time they lose their resistance to freezing and boiling. If you live in an extremely cold or hot climate, this means you may find you won’t be able to start the engine one day or that you will suffer an expensive boil over. Engines contain quite a number of parts in the cooling system that rust. This rust is picked up by the coolant during circulation and deposited somewhere else. This is usually the radiator and smaller opening in the cooling system. Regularly and properly flushing the engine will prevent this and combat sometimes fatal cooling system blockages. Other cooling system components corrode in other ways, allowing particulates to clog the cooling system.

Flushing properly removes all of these contaminates and exchanges the old and tired coolant for new.

How it Works

The way most shops are doing this now is with a machine that has a supply of fresh coolant in one container and another, empty container to recover the used coolant for recycling. The thermostat is removed and the heater is turned on. The engine is then started, which allows the water pump to pull fresh coolant and push the old coolant out. Once all visible traces of rust and other contaminants are gone from the effluent stream, the system is turned off and the cooling system is resealed and topped off. Another similar method has the engine turned off and the thermostat removed. The upper radiator hose is then removed and fresh water is forced through the cooling system with compressed air. Once the outflow is completely clear, the system is drained, the thermostat is replaced and the proper coolant ratio is added.

Determining Need

All car makers specify certain intervals for every possible maintenance item. As a pure function of time and mileage, most car makers recommend an engine flush every year or twelve to fifteen thousand miles. As a general rule of thumb, this is an ok guideline to go by. However, there will be times when you may need to flush the engine more or less often. To check if you really need to flush the engine, place a clean container under the drain valve and open it. Allow enough coolant to drain to see the color of it and, if possible, to see the cooling tubes in the radiator. If the coolant looks like it has rust in it, or you can see that the cooling tubes are clogged, it’s time to flush the engine. One other way to check is to monitor your coolant overflow reservoir throughout the day. If the level fluctuates greatly, your engine is most likely not being cooled sufficiently and you should flush the engine.

Like changing your oil, if you allow your coolant to exceed its useful life for too long or rust to build up, you will very likely end up with a very expensive bill to either rebuild or replace your engine. Knowing how to recognize when you need to flush the engine can help you prevent this.

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