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Ford Mustang GT 1996-2004: Why is My Car Overheating?

An overheating engine is nothing to take lightly, especially with a Ford Mustang GT. Let's look at a few of the reasons why this might be happening.

By Ben Mannino - October 22, 2015

This article applies to the Ford Mustang GT (1996-2004).

So your Ford Mustang is overheating, and you're not quite sure where to begin? The engine cooling system involves many different components, and any one of them can be the culprit. There are times where one part can go bad and take another one down with it. This is not something to work on tomorrow, as overheating can do some serious damage to your engine. Here are a few of the more common problems to look for.

Materials Needed

  • Flashlight
  • Cooling pressure tester
  • Multimeter

Step 1 – Pull over

If you're driving along the road and your Mustang starts to overheat, you need to pull over as soon as you can. Be sure to turn on your heater, which sounds crazy but it acts as another radiator, bringing the coolant temperature down until you can turn the car off.

Figure 1. Turn up the heat to cool down the engine.

Step 2 – Start simple

The radiator's job is to cool down the hot liquid coolant flowing through your engine. Air flowing over those little metal "fins" is what reduces the temperature of the coolant. It is very easy for something to block the flow of air through the radiator, seriously interfering with its intended purpose. Look at the area around the radiator for any type of blockage; leaves, plastic bags or mud can all easily clog up the front face of the radiator, as shown in Figure 2.

Figure 2. Leaves can restrict air flow.

Remove any strange objects, and spray the area with a garden hose to remove any dirt or sediment. That could easily be the cause of your problem, and you won't find an easier repair job for any vehicle.

Step 3 – Are you losing coolant?

Check under your vehicle for any leaks. All anti-freeze is different, and some can be red or yellow in color, making it easier to spot. If you find coolant, you have a system leak somewhere. Flash a light from the top and the bottom to see if you can find it, but the leak may not be that easy to spot. A cooling system pressure tester is is the best way to get results fast. It's a pump that you plug into the top of the radiator and force air into the system. Pump it up to the pressure indicated on the radiator cap (no more than 15 to 16 psi) and no more—you don't want to create a new problem.

Figure 3. Pump up the coolant system to find the leak.

If there are no leaks, the pressure indicator should remain steady. If it drops, then you definitely have a leak. It could be external, as in the case of a leaky hose, or internal to the engine (blown head gasket). Most of the time the leak will be obvious, by sight or sound, as the coolant sprays out from the affected area. If no leaks are found, move onto Step 4.

Step 4 – When does the overheating occur?

If the car overheats at idle or at lower speeds, check your fans. They should be cycling on and off at regular intervals to keep the radiator cool. To quickly test this, run the air conditioner and that should immediately start the fans spinning. If the fan does not kick on, it could be defective, or you could have a blown fuse or bad relay. If you have a mutlimeter, check the voltage at the connector when you turn on the A/C. If you're getting power, then you can be sure the fan is no good. No power is a good sign that you have a bad fuse or relay.

Figure 4. Check the fans.

Step 5 – Still overheating?

These are the common issues when it comes to overheating. If all these tests have passed but you still have the problem, then it's time to dig a little deeper.

The thermostat opens and closes to allow the coolant to flow from the upper radiator hose into the engine when the temperature reaches a balmy 220 degrees. Sometimes it gets stuck, keeping the coolant from flowing properly. Squeezing on the hoses (with a wet towel) will reveal if the coolant is bottled up in one spot. The good news is that the thermostat is a relatively inexpensive part to replace.

Figure 5. Check the thermostat.

Air in the system can also negatively affect the cooling process. This happens when a part of the cooling system gets replaced without bleeding the coolant system afterward. In this case, you will need to do a complete coolant bleed to get all the air out of the system.

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