Coolant flows through your engine block and the head is propelled by the water pump. The circulation and temperature are regulated by your thermostat and radiator fans, and the fans are triggered by fuses & relays that turn the fans on/off at a predetermined temperature. The temperature is monitored by a temperature sensor, which relays that information to the vehicle’s engine control unit (ECU) for proper management
Engine overheating symptoms
High-temperature gauge reading
Water steam from the engine
Water bubbling noise
Engine overheating causes
Malfunctioning fuses, relays, or wiring in the cooling circuit
Coolant quantity and quality
Blocked/leaking radiator unit, failing radiator fans & stack radiator cover
Stuck open or closed thermostat
Faulty temperature sensors, pressure sensors, or ECU
Water pump, serpentine belts broken
Engine Over Heating - DYI Steps to fix it
STEP 1: Verify that the radiator fans are spinning.
Open the hood or bonnet as it's sometimes called, and wait for a few hours to cool the engine down. Refill the radiator tank with water for now, since you will not use an expensive coolant for such a test. Start the car and keep topping the water until you realised the tank is totally full to the brim.
With the radiator cap removed inspect to see if the water in the radiator is flowing, if not you might be using a thermostat that is not open yet since the coolant temperature has not exceeded the operation value or might be experiencing blockage in the tank. Continue observing the cooling fans if it’s spinning. If not, it’s possible the desired operating temperature has not been met. Push it to work by turning your A/C on if your car A/C works anyways. If your car A/C does not function, turn rather the defrost switch on to bypass the relay trigger, while you monitor the temperature gauge inside your dash. Turn the car off if the temperature goes past half the reading In either case if the fans do not spin or run, you either have a faulty fan motor, or a defective cooling fan circuit.
STEP 2: Test cooling fans for operation.
Now let’s test the cooling fans for functionality. You have small technical skills fine. Connect two separate wires with one end to the battery positive and negative post and the other end to the fan connectors with the main fan connector disconnected. Polarity is not an issue here since fans can spin in both directions. If the fans spin viola, you have a circuit problem, if it doesn’t spin replace the fan motor. If the fan issue was just fixed by a technician, place a note or paper in front of the radiator, in between the radiator and condenser, and see if the note or paper will be blown away or get stuck to the radiator. If it gets stuck fans are spinning in the right direction, but if blown away, it can raise overheating issues as well. Next is to verify the cooling system circuit,
STEP 3: Verify the cooling system circuit integrity.
Now that you know your fans are spinning after testing them with a direct connection to the battery, pop up the fuse box, and with the test light locate the fuse for the fans and test it. If it's not broken or open, identify the relay and check that as well. If you’re not experienced with this level of diagnosis, report this issue with Adeiyie using this link SERVICE CALL. Relays always have a hot 12 volts always present on one of the four (4) pins sockets mainly for the switch circuit. Test to verify its presence. There is also another 12 volts present only when the key switch is turned to power the coil on one of the four (4) pins socket. Since a relay circuit has 2 circuits (a coil and a switch) you need power for each circuit to function. If you’re getting both voltages using your test light or multimeter, look for the grounds as well on one of the (4) sockets by tuning your digital meter to ohms reading and connecting one of the DMM probes to the chassis and the other probe to any of the other unidentified pins (I.e. the pins without the 12 volts you just checked). You must see a low ohm reading indicating that is the ground circuit for the control side that is the coil. The last non-tested pin must be the socket that sends power to the fans. Using a fused jumper wire bridge the pin with fixed hot all the time is 12volts and the non-tested pin suppose to be the contact point to the fan. If the Fan spins, you have to replace the relays. If the fan does not spin, find out from a wiring diagram what controls the ground side of the coil - is it computer-controlled or normal ground control?
In situations where fans are computer controlled, the ground on the other pin as indicated can only be tested by turning the key on with the engine off, whiles your digital meter probe is connected to the battery post and the other normally the negative probe to any of the last two pins of the relays apart from the two identified pins with 12 volts reading. You must get a 0-volt reading on your multimeter since there is a current flow. Turn the key OFF and see if the reading will change to 12v. If it does computer control integrity is good, if not check the control circuit of the computer. To verify computer operation, try to be the computer using a test light grounded and touch the ground side of the relay while the key on the engine is off or running. If the fan spins, check the computer circuit for map functions. With a computer control unit, there is always a fan switch module, thermostat, or coolant temperature sensor, and PCM working together to regulate the fan speed. find out more using the wiring diagram.
If the 12volts hot all the time at the switch side of the relay and the key switch when turned on is missing, diagnose the circuit for open wiring or high resistance but not shorts, because shorts will always open a fuse. At this juncture, if you cannot continue, report this issue with Adeiyie using this link SERVICE CALL.
STEP 4: Check for cooling unit accessories if the fan circuitry is good.
Now that your fan spins, because the circuitry is in good condition, inspect the radiator tank and hoses for leaks. Replace hoses or radiators if leaks are found. This is why it’s important to use coloured coolant. You can always determine leakages using the colour left on the hoses. Leaks not only let coolant out, but they let air in. Chances are high that if you had a major leak, that would be one of the first things you noticed. However, small leaks can be just as problematic and do not always leave a puddle on the ground. This can only be identified with the engine running.
Ensure that the serpentine belt responsible for turning the water pump and other engine accessories like your alternator is still installed. Sometimes these belts break while driving and leave little to no trace that the belt was ever there, leaving the water pump unturned and generating overheating. If the belt is there, double-check that it is tight. If the belt feels too loose, tighten it with the tension adjustment screw. Many times this screw is found on the alternator or power steering bracket. Too tight will let it snap under load, so be mindful of that.
STEP 5: Check the thermostat, coolant temperature sensor & water pump operation.
When a thermostat goes bad, it will either be stuck open or closed. If it gets stuck closed, the coolant will not circulate properly. If it’s stuck open, it will take a longer period for the engine to reach its operating temperature condition, because water has already started circulating, cooling the system before working temperature. In our part of the world, the thermostat is always removed to prevent overheating issues due to our hot climate conditions. Although it’s not the best of preventive measures, the coolant temperature sensor compensates for that, by signalling the PCM to control the heating and cooling circuitry. Fans are brought up to speed to cool down heating components. In order to check a thermostat, you will need to drain the coolant and remove the radiator neck - that the radiator hose attaches to it. Place the thermostat in the boiling water for a few minutes and then remove it. It should be open when removed from the water and slowly closed as it cools. For the Coolant temperature sensor, use a scanner. More info about checking or troubleshooting Sensors.
At this point, if you have not found the problem, the cause of the overheating condition its likely there are other issues. The water pump may be bad or you may need to replace a head gasket. On the extreme end of this, the engine/head could be cracked or warped. If you end up with any of these problems, there will be a significant amount of work that would be necessary to fix them. The water pump is the best-case scenario if you end up this far. A water pump replacement is not the hardest procedure to do on your own, but if the head gasket is blown or the engine block or head has warped or cracked, then the vehicle will likely need professional repair as those jobs are beyond the scope of this particular walkthrough.
Schedule Car is overheating diagnostics.
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