Rick's Free Auto Repair Advice

What to do if your car overheats

How to prevent engine damage when your car overheats

What causes your car to overheat?

If any of the cooling or engine components fail, your car overheats and you’re faced with an emergency situation and some major decisions. Deciding whether to keep driving or call a tow truck depends on which components failed. Here are the most common causes of car overheating:

• low coolant level

• radiator fans not working properly

• thermostat stuck shut

• Water pump serpentine or dedicated drive belt failure

• Clogged radiator tubes

• Clogged radiator fins

• head gasket leak

First things to check when your car overheats

1)      Stop and check for coolant leaks on the ground.

2)      Check the coolant level in the coolant reservoir.

3)      Check for a broken, missing or slipping water pump drive belt

4)      Check radiator fan operation

What to do if you find coolant on the ground after stopping

If you find coolant on the ground when car overheats, coolant leakyou stop, chances are you’ve got a fairly large cooling system leak. Even if you refill the coolant reservoir, you run the risk of causing major engine damage if you continue driving. Bottom line: If you detect overheating and stop the vehicle to find coolant on the ground, call a tow truck. Do NOT add stop leak products. Do NOT continue driving—you can cause unnecessary engine damage ranging from a $1,500 head gasket repair to total engine failure costing several thousand dollars.

What to do if you have a low coolant condition?

If you discover a low coolant level in

low coolant level, car overheats

44579883 – coolant reservoir under the hood of a car

the coolant reservoir but don’t see any evidence of leaks, add coolant or water to the reservoir and run the engine at idle to see if the temperature drops to the normal range. If so, you can continue driving until you can find the leak and have it repaired. If the engine doesn’t cool down, call a tow truck. Do NOT add stop leak products. Do NOT continue driving—you can cause unnecessary engine damage ranging from a $1,500 head gasket repair to total engine failure costing several thousand dollars.

What to do if your radiator fans aren’t running?

Most late model vehicles have an electric multi-speed radiator fan or several fans. Electric radiator fans are designed to run in several modes. The first mode is triggered by the engine coolant temperature sensor. When the sensor detects a rising coolant temperature, the PCM/ECM activates the low speed feature of the radiator fan. If the engine coolant temperature doesn’t fall to normal range within a set period of time, the PCM/ECM will command a high speed mode or turn on a second fan.

IF your engine overheats and your electric

radiator fan relay

Fan relay

fan isn’t running, check the radiator fan fuses first. IF the fuses are good, check the fan by hand (engine off) to see if the fan blades rotate smoothly. If so, the fan motor is probably good and the problem may be isolated to the relays. See this post for more information on fan relays.

Next, turn your AC to the MAX setting and see if the fans go into high speed mode or the AC activates the second radiator fan. If the fans work, idle the engine to see if the coolant temp drops to normal range. If so, you can drive it to the nearest repair shop as long as you monitor engine temp as you drive. If the engine temp rises to the danger range, the AC trick won’t work and you’ll have to call a tow truck.

What to do if your water pump belt breaks or slips?

Driving with a worn, broken, missing or

serpentine belt, water pump belt, car overheats

Torn/worn water pump belt

slipping water pump drive belt is a great way to cause major engine damage. The overheating can damage heat gaskets, costing around $1,500 or even destroy your engine. If you don’t have a spare belt or the tools to install a new belt, call a tow truck. It’s better to spend $150 on a tow than $1,500 on a head gasket repair job.

What to do if your radiator fins or tubes are clogged?

Radiator fins get clogged with bugs, leaves, dust and dirt and that restricts the airflow through the radiator, causing overheating. If you detect crud buildup on the front of the which antifreezeradiator fins, try washing off the debris with water. Then idle the engine with the AC set to MAX (to activate the high speed or second fan) and see if engine coolant temperature drops. If so, you can drive to a repair center or home as long as you continually monitor the coolant temperature.

If you find the radiator tubes clogged with rust, there is nothing you can do to remedy the situation while you’re parked on the side of the road. The only fix for clogged radiator tubes is a cooling system flush or a new radiator. Be warned that flushing a severely corroded radiator can remove rust buildup that’s plugging pinhole leaks. After the flush, you may experience leaks. At that point, your best option is to replace the radiator.

Turn heater on high to cool engine?

Turning your heater on full blast used to be a tried and true method to help you get home or to a repair shop when your car overheats. But that was back in the days when all engines were cast iron. With newer aluminum engine blocks and cylinder heads, relying on the heater to pull enough heat out of an overheating engine is RISKY. Here’s why:

• If the water pump isn’t working, you won’t get coolant flow through the heater core. In that case, turning the heat to full blast won’t help at all.

• If the thermostat is stuck closed, you won’t get coolant flow through the heater core. In that case, turning the heat to full blast won’t help at all.

• If the overheating condition is caused by a leak, system pressure will be low. A properly operating cooling system runs around 16-psi. The boiling point of coolant increases 3°F for every 1-psi. At 16-psi, system pressure, coolant boiling point rises to 260°F. If the system leaks, you lose pressure and the coolant will boil. No amount of heater core action can compensate for coolant boiling.

• If the radiator fans aren’t working, the coolant can’t shed enough heat as it passes through the radiator. So the coolant flowing into the engine through the lower radiator hose will be close to the heated coolant leaving the engine through the thermostat. In effect, you’re recirculating super-heated coolant and adding more and more heat with each circulation. Even IF you have a working water pump, most automotive heater cores only pull a small fraction of heat out of the coolant.

Tow versus driving

Nobody wants to pay for a tow. But the risks are SO high on an aluminum engine that it makes little to no sense to try and limp home when your car overheats. Overheating can warp the cylinder heads, causing the head gaskets to leak. The coolant can leak into the oil pan, which can totally destroy the engine bearing. At that point you’re looking at a new engine for around $3,000.

No matter how you slice it, a $150 to $200 tow will always be cheaper than a damaged engine. Can’t afford a tow? How in the world are you going to afford a $1,500 head gasket repair or a new engine?

©, 2018 Rick Muscoplat


Posted on by Rick Muscoplat

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