Engine Cooling System Problem

     Do you know how the cooling system in a car keeps your engine from overheating. Well lets see if I can explain so you can understand it. It starts with the radiator and makes it way into the engine thru the water pump, circulates thru the engine, out thru the thermostat back to the radiator. That's the way the coolant flows. Now lets look at it in a little more detail. The radiator is just a big heat transfer device. It holds the coolant that comes from the engine and cools the coolant by air passing the fins of the radiator, taking the heat out of the coolant before sending it back into the engine. Air passing thru the fins comes from 2 things, the vehicle traveling, and a fan pulling air thru. Most all cars today have a electric fan on the radiator. This fan only runs when the coolant gets to a certain temperture, usually around 215 to 230 degrees. These vehicles now days run on the tip of overheating. The coolant in the radiator is sucked out of the radiator by a water pump.It is pumped into the engine where it flows around the cylinders, then up thru the heads, to the thermostat. The thermostat works off the temperature of the coolant, they are usually set to open at 195 degrees. So once the engine gets to 195 degrees and above the thermostat stays open, the coolant flows into the radiator where the heat is taken out and the process starts over again.

              So lets look at why or what makes a engine overheat

Lets start by when is your car running hot, does it run hot just sitting, or when your traveling.

Overheats sitting, like at the bank, stop light or drive thru


    Looks like the coolant fan is not turning on, could be a fuse, coolant fan relay or a ECT(engine coolant temp sensor)
which tells the computer what the temperature of the engine is at. May also be a bad fan motor. How do you tell which one of these things are the problem. This is where you are going to need a test light.1st,find the fuse panel and find the coolant fan fuse, check it by taking your test light lead and find a good ground, touch the positive post on battery to see if your test light is working. Then take the test light and touch both of the little slots in the top of the fuse, making sure that both sides light up. If both sides light up fuse is good, move over to the relays and find the coolant fan relay. Pull the relay and turn key on, take the test light and probe each slot in the panel where the relay was plugged in. You should get 2 slots that light up,one lights up all the time, one lights up only when key is on. You should have 2 more slots left, one goes to the fan motor and the other is a ground from the computer. The computer grounds the relay and makes the relay come on and makes the fan run. Get you a jumper wire and jump from the positive post of battery to the slot that goes to the fan, that would be the slot that is not hot from the key or battery. Just touch the slot and see if the fan comes on.If fan comes on the problem is with the relay or computer system. If it does not come on, find the wire plug on fan motor and pull off. If you can get to the wire plug on the fan motor, pull it off and then take your test light and hook it to the positive post of the battery, touch each wire going to the fan, we are looking for the ground wire. Note color of the wire that lights up the test light, if neither wire lights up you have a ground problem. If light comes on, move the test light lead to the negative post on the battery. With test light hooked up to negative post on battery, and the other end to the wire going to the fan motor that is not the ground wire, jump the slot where relay goes with your jumper wire still hooked to positive post of battery and see if test light comes on when jumper is inserted into slot of relay. If the light comes on the fan motor is no good. A lot of times you can swap relays around in panel to see if it might be a bad relay.If you still can't fiqure out you problem e-mail me or leave a question in the forum.

       Overheats driving down the road
How fast does the engine get hot. Does it get hot before you get to the end of the block, does it get hot after you drive for a couple miles. Does it get hot pulling a trailer or camper, does it get hot after driving a long way.

                          If it overheats before you get to the end of the block 
    Probably a bad thermostat, let car cool off and if you can get to the thermostat housing, pull the thermostat out and put housing back on and drive the car without the thermostat and see what happens. If car runs cool, the thermostat is bad. You can replace the thermostat or not. The function of the thermostat is only to warm up the engine quickly and to slow the flow of the coolant.

        Is the engine overheating after driving a few miles or less
    It might be a head gasket leaking compression gases into the coolant system. The way to check and see if that's the problem,let car cool down, better if you wait till engine is completely cooled down. Make sure radiator or coolant jug is full to the top with water or coolant. With the cap off, start engine and see if coolant comes out of radiator or jug, the water pump should suck coolant down, but if the coolant comes out a little, speed engine up and see if the coolant comes out quicker,if it does the engine as leaking head gaskets. It could also be running hot because of water pump, to check and see if water pump is working, you can do this. Find the heater hose outlet going to the heater core. There will be two hoses going to the heater core, pick the easy one to get to and pull it off, some coolant will leak out, wait till it stops leaking. When it does, then go start engine and the coolant should start pumping out of the fitting on the engine or coming out the hose end.
If you speed engine up the flow of coolant should speed up, if it does water pump is working.

                                    If it takes the engine a long way before it overheats
     It could be a radiator plugged up, one way to see if this is your problem, is to turn the heater on full fan speed and see if the engine cools down. If the engine cools down radiator is bad. If it gets hot while AC is running look for AC condenser fan not working or fan clutch not spinning fast enough to cool both AC condenser and radiator together. Turn AC off and see if engine cools down, if it does, you have a bad AC coolant fan or fan clutch.

                                                    Engine Cooling System Leaking
     Hey is your engine running hot because your car keeps losing its coolant. Looked for a leak and couldn't find it. What do you do. The parts house sell some stuff called cooling system leak detector. You put it in the radiator and fill radiator with water or coolant, drive the car a few miles. Now this stuff works with a black light, you can buy a cheap light from the parts house also. Shine the line under hood all over the engine, top, bottom, front and back of engine. If you still don't see a leak around engine or radiator system. Then find the drain hole for AC drain and see if there might be a green coating around or leaving the hole, if it does, you have a heater core leaking. One more place this stuff can show up is in the tailpipe, if the inside of tailpipe is glowing green, you have a head gasket leaking. Also pull oil dip stick and see if oil looks like a chocolate milkshake, if it does you have a internal coolant leak, does not mean you have a head gasket leaking, you might have a intake manifold leaking. If you have a radiator pressure tester you can pump up the pressure in the cooling system and check for leaks.