How to Bleed Radiator

Just so you know, the only radiators that ever need 'bleeding' are the systems on (usually front wheel drive) vehicles, where the point where you add the coolant is lower than the highest point in the cooling system. Since water does not go 'up hill', you will need to open a bleeder screw at the top of the cooling system (usually where the top radiator hose meets the engine), while you fill the system up. If you do not do this, then there will e a big air bubble in the top of your cooling system and the coolant will not be able to circulate through the engine, and make things overheat.

The only time you need to bleed the cooling system in your car, is when you work on it, and fix the leak or other condition that caused it to have to be opened up and worked on in the first place. This is not something that you do as a 'maintenance item', but the final steps in working on certain cooling systems, as mentioned above. It is no longer necessary to change the coolant on newer vehicles, as they are equipped with (pricey) lifetime coolant. The only time you need to buy any of this stuff is when you had some leak out. When you make a repair to the cooling system, you can pour the same coolant right back in the engine that you had to drain out of it.

The best way I know to tell you how to do bleed the system is to explain to you exactly how I do it. So here goes! Okay, you have fixed the cooling system, and now you are ready to fill it back up. So pour in the proper coolant mixture for your car in the cooling system reservoir until it comes to the top, and you cannot add any more. Then look at the point where the upper radiator hose meets the engine. This is usually the thermostat housing. The thermostat should be changed as a maintenance item, see your owner manual for the maintenance intervals. Anyways, on that thermostat housing, there should be a small bleeder screw. If it is not on the thermostat housing, just look for the highest point on the engine, ad there will be a small bleeder screw (if your vehicle requires it) If not, then don't look too hard for it, because your vehicle might not even need one. At this point you are going to open (or remove) that screw.

Once the bleeder screw is out, you can crank the engine and turn the heater on. Turning on the heater circulates the coolant throughout the entire cooling system, so you can 'chase' the air out of it. So with the heater on, and the bleeder screw open, add the rest of the coolant until it comes out the bleeder screw without any air bubbles. It should be a steady stream. Once you get that steady stream of coolant, you can replace the bleeder screw, and the radiator cap. Continue to let the engine run, while you check your work for leaks. A good way to find out if there is a leak is to place a clean piece of cardboard under the engine and areas of it that you were working on. If anything drops down on that cardboard, you will be able to see it right away.

At this point I will assume that you do not have any leaks, so continue to let the engine run until it gets up to the normal operating temperature. This is when the electric fans will turn on. One the fans turn on, let the engine run for about ten more minutes. This is important because if there is an air bubble in the cooling system, then it will start to run hotter than normal in this time. If it does start to overheat, you will need to, bleed the system again, and try again. If it still overheats, then you will need to double check your work on the repair (because it probably wasn't fixed right or the wrong parts were changed. I have written an article about how to diagnose cooling system problems that has helped many people, and here is a link to that, if you need it.

Hopefully you can get your car back on the road with as little headaches as possible with the help that I offer you in my articles. I hope they are as informative to you as it brings me joy to be able to share my knowledge with others. Thanks for reading, and keep it cool!
If your engine is running hot, then you will want to read how to diagnose an overheating engine. The first thing to look for is air in the cooling system, so here is how to bleed the engine cooling system. If air keeps getting into the cooling system for no reason then you might have to diagnose a cracked head. Other causes of head problems would let themselves be known by white smoke from the exhaust. Of course, water in the oil does not have to mean head problems, so make sure to read about different causes of water in engine oil. If you do not use Anti-freeze, or engine coolant then you should know what to do when water freezes in your engine. If you live up north then you will definitely want to know how to install a block heater in your vehicle, for all those cold mornings, too. Remember, if the Radiator comes out to have different temperatures, it could be dirty, or it might be time to change the radiator.