210 is not overheating. Obviously 260 degrees is, but there are a lot of vehicles, GMs in particular, that don't even turn on the fans until 220 degrees.
I don't make up the codes. Is it possible that code has been in the computer since winter? Remember, that code doesn't turn on the Check Engine light, so you'll never even know it was set. If your gauge is as accurate as you think it is, that code will set if the engine stays at 160.
The next thing to consider is getting an inexpensive scanner so you can view live data and see exactly at what temperature the engine is running. There are units out there that take a few seconds to update the readings, so they aren't good for some tests, but for something like this they will work just fine. I have one to borrow out that cost less than fifty bucks.
As for running hot, there are some things to look at when it's a vehicle you're unfamiliar with, meaning unfamiliar with its history. Specifically, look for the rubber seal under the front edge of the hood, and check for plugs and flaps missing on the core support. Either of those will allow air to bypass the radiator. Some people mistakenly think the engine will cool better if they take the shroud off the radiator to get more air flow, but in reality, that lets the air go through the radiator, then back around and go through it again. The same air keeps getting reheated so it gets hotter and hotter and doesn't cool the radiator.
Sometimes people add oil and transmission coolers and those present too much obstruction to air flow. If your radiator fan is powered by power steering fluid, be sure that unit is working. You said your fan is working, but stupid as this sounds, check that it's spinning the right way. Some replacement fan motors are somewhat generic and can be used in more applications if it doesn't come with the connector body. You're supposed to plug the terminals into your old connector body. Even when you understand that those terminals can't be switched, you can't be sure the person who assembled the motor soldered the correct wires together. Just tonight I helped a friend figure out that someone poked the only two wires for an ABS wheel speed sensor in the wrong holes in the connector. This is the first time I've ever seen a wheel speed sensor with a polarity, so it was not something we thought we needed to check for.
For a quick check too, when the gauge says the engine is over 220 or 230 degrees, feel the upper radiator hose. Normally they get too hot to hold onto for very long, but you can stand it for a few seconds. If the coolant really is at 220 degrees, the hose will burn your hand if you try to keep on holding it.
Feel across the radiator for cold spots. If you find any, those tubes are plugged. Have the coolant checked for freeze point. The testers that use floating balls or pointers are only accurate down to about minus 50 degrees. From there, if you add a higher concentration of antifreeze, the tester will show a colder freeze point, but the actual freeze point will go up closer to 0 degrees. The lowest freeze point you can get is with 70 percent antifreeze, not 100 percent. The reason those testers incorrectly indicate a colder temperature is they simply compare the weight of the coolant to the weight of straight water. To get the most accurate reading, you need a "refractometer". Those are relatively expensive, and for most shop use they are not needed, so very few mechanics have them.
The reason for testing the freeze point is if someone added too much antifreeze and not enough water, the freeze point might falsely appear to be really good, but antifreeze can't hold as many BTUs of heat as water does. That means that almost any engine could overheat if it has just antifreeze in it. The coolant can't absorb the heat fast enough as it flows through the engine, and it can't flow fast enough to get that heat to the radiator. The cooling system is most efficient at doing its job when it has only water, but we still need antifreeze for its corrosion inhibitor and water pump lubricant additives.
The last thing to consider is having a chemical test performed at the radiator for a leaking cylinder head gasket. That involves drawing air from the radiator, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow. Combustion gases that sneak into the cooling system can pool under the thermostat and cause it to not open. Thermostats have to be hit with hot liquid to open; hot air won't do it.
What do you mean by a "fail safe" thermostat?
Wednesday, June 24th, 2015 AT 9:24 PM