Proper Coolant Temperature and Camshaft Life!

Have you ever tried to find what proper coolant temperature is for most automotive engines? There are a lot of people who think they know, but it is difficult to find specifics, even in textbooks. We know we want the intake air to be as cold as possible (for best power) because cold air is denser (there are more oxygen atoms per cubic foot). The coolant temperature, however, is a different matter. The internal combustion engine changes chemical energy stored in gasoline into heat energy that is focused on the piston tops. If the cylinder heads and engine block are too cold, they will absorb much of the combustion heat before it can be used to push the piston down the cylinder. If the engine gets too hot, engine lubricants can break down, as well as overheating of the intake charge can lead to detonation, etc.

It turns out that coolant (usually a 50/50 mixture of coolant and water) has some fantastic properties that are ideal for use in engines. With a properly pressurized cooling system, coolant will not freeze until –30°F, and it won’t boil until +270°F (new oils don’t start to break down until well over 270°F). With these characteristics, engine designers have decided that engines should operate at approximately 210-215°F. Why, you ask? Well, it has to do with operating the engine at a high enough temperature to boil water out of the oil after the engine is cold started. If you have dew on the grass, it is certain that you have water in your oil, as the crankcase is open to atmospheric pressure! You can either remove the water by draining it out the bottom of the oil pan (remember the oil floats on water) or run the engine long enough and hot enough to boil the water out of the lubrication system. Years ago, coolants weren’t as sophisticated and engines were run at 165-180F, but the oil was changed every 1000 miles or so. That’s why many old timers think engines should run at 165-180F. Have you ever noticed that Ford doesn’t put temperature marks on their gauges? They just mark C for cold and H for hot and write “normal” through the center. If you hook up a scan tool to a GM, you will often find that the gauge reads much lower than the coolant temp sensor. That is because they know most drivers don’t understand how hot an engine should run.

So what does this have to do with camshafts? Many enthusiasts erroneously think that the colder their engine runs the better! If they are not running the engine hot enough to boil the water out of the oil, the oil becomes contaminated and the lifter/cam lobe interface is the highest load point in the engine. Engines running too cool can contribute significantly to camshaft and lifter failure. Think about it: What good does it do to use the most expensive synthetic oil and then run the engine so cold that it is contaminated by water vapor??!! Another point, piston manufacturers’ piston-to-wall clearance recommendations assume you will be running the fully warmed engine at 200°+F. Run the engine too cold, and you could see some scuffed pistons because the cylinders had not expanded enough to provide clearance.

If your engine will only run its best at the drag strip with the engine at 165°F, you probably have too cold of a spark plug heat range and you are probably jetted way too rich! If you keep the engine hot (not the intake charge), you will be using more of the heat energy in the gasoline to make power instead of just heating up your block. It does take “tuning know-how” to run an engine at 200-210°F, but you might be surprised how well and how long it runs when you do!! One final point - running a computer managed engine at 165°F compared to the factory 210°F will often cost you as much as 4 MPG. The reason for this is that the computer thinks that the engine is not off the “choke cycle” and it is still putting out a rich mixture! Check the science on this and don’t pay attention to the “old wives tales” of the past. Materials and lubricants are much better and different today than they were in the past!!