origionally posted by Shawndude:
With old cars like ours, it is not uncommon to experience overheating issues. To solve this problem, one must work in a logical manner, to rectify the situation. This is a simplified tutorial to get you pointed in the right direction.
Quick check list:
1) Signs of a Bad Head Gasket? Replace the radiator cap.
2) Is your cooling system leaking?
3) Cooling fan working? Is cooling fan shroud in place?
4) Thermostat working? Replace it.
5) Radiator clean, inside and out?
6) Cooling system free of air?
1) Verify you do not have a Bad Head Gasket. Most obvious symptoms of a BHG are:
- White dense smoke from the tail pipe. The vapors smell sweet.
- Overflowing radiator reservoir. If you find the coolant is coming out of the radiator reservoir, install a new radiator cap. If this does not fix the problem, chances are very high you have a BHG.
- Radiator reservoir requires coolant to be added, even though it isn't leaking out.
- Inconsistent coolant temperatures. The gauge needle may be spiking up and down at a fast pace.
- Coolant appears milky and slimy to touch, indicating oil.
- Oil has a white milky look to it, with water droplets forming, indicating coolant is mixed with it. You can see this on the oil dip stick.
2) If the cooling system leaks, it will make it impossible to troubleshoot any other problems until this is repaired. Check for green puddles under the car after it's parked. Open up the hood after driving and smell the engine. If you smell a sweet odor (like when cotton candy is being made) there is a leak somewhere. Look at all the hoses and watch for any green fluids indicating coolant. Many times you can also hear bubbling sounds which will lead you to the source. Last check is to squeeze the upper radiator hose after the engine has been shut down while hot. The hose should be very firm to the touch. If you can squeeze the hose significantly, it indicates a leak, or a faulty radiator cap.
3) If the car is only overheating in stop-and-go traffic, it is a very strong indication your cooling fan is not working properly. To test the cooling fan, drive the car for at least 30 minutes so it is nice and hot. Shut off the engine and open the hood. With your hand try to spin the cooling fan. It should offer resistance to the movement, and only spin about half a revolution. If it keeps spinning without much resistance, your cooling fan clutch is broken, and you must purchase a good unit, or install electric cooling fans. Also grasp the cooling fan and see if there is any free-play or wobbliness. If there is, it could break off causing much damage. Make sure to replace it.
4) If the car overheats at highway speeds and in stop-and-go driving, first step is to change the thermostat. You can test your unit, but they are so inexpensive that it makes sense just to purchase a new one. Many car parts stores carry a high-flow units. The factory temperature is 190F, but you can install a 180F unit without any problems.
5) Clean the radiator! If the radiator is the original Toyota unit, it is most likely internally clogged up. I would strongly suggest purchasing a new unit from the aftermarket vendors, they cost about 150 dollars. If you do not want to purchase a new unit at this time, remove the radiator and clean it inside and out by flushing with water. Many Supras collect lots of debris where it is not visible. See the picture at the end of this post, obtained from: http://www.supras.com/~riemer/sonictech/cooling/radairpluged.html
6) Purge any air from the coolant system. While air in the coolant will not make you automatically overheat, it can add to the problem. The most obvious sign of air in the system is a spiking temperature gauge, and "gurgling" noises coming from the dash area (heater core is located there). Unfortunately these are also signs of a BHG. The simplest way to purge most of the air is to start with a cold car and remove the radiator cap. Start the engine up, and let the car warm up. Keep adding coolant or water to the radiator neck while it's running. When the thermostat opens, you will see the coolant level drop, or lots of air bubbles come out. It helps if you rev up the engine to about 2000 RPM. When the coolant level is stable and the thermostat is open (look at the temperature gauge), put the radiator cap back on. Any remaining air will purge itself during driving, in a healthy system.
With old cars like ours, it is not uncommon to experience overheating issues. To solve this problem, one must work in a logical manner, to rectify the situation. This is a simplified tutorial to get you pointed in the right direction.
Quick check list:
1) Signs of a Bad Head Gasket? Replace the radiator cap.
2) Is your cooling system leaking?
3) Cooling fan working? Is cooling fan shroud in place?
4) Thermostat working? Replace it.
5) Radiator clean, inside and out?
6) Cooling system free of air?
1) Verify you do not have a Bad Head Gasket. Most obvious symptoms of a BHG are:
- White dense smoke from the tail pipe. The vapors smell sweet.
- Overflowing radiator reservoir. If you find the coolant is coming out of the radiator reservoir, install a new radiator cap. If this does not fix the problem, chances are very high you have a BHG.
- Radiator reservoir requires coolant to be added, even though it isn't leaking out.
- Inconsistent coolant temperatures. The gauge needle may be spiking up and down at a fast pace.
- Coolant appears milky and slimy to touch, indicating oil.
- Oil has a white milky look to it, with water droplets forming, indicating coolant is mixed with it. You can see this on the oil dip stick.
2) If the cooling system leaks, it will make it impossible to troubleshoot any other problems until this is repaired. Check for green puddles under the car after it's parked. Open up the hood after driving and smell the engine. If you smell a sweet odor (like when cotton candy is being made) there is a leak somewhere. Look at all the hoses and watch for any green fluids indicating coolant. Many times you can also hear bubbling sounds which will lead you to the source. Last check is to squeeze the upper radiator hose after the engine has been shut down while hot. The hose should be very firm to the touch. If you can squeeze the hose significantly, it indicates a leak, or a faulty radiator cap.
3) If the car is only overheating in stop-and-go traffic, it is a very strong indication your cooling fan is not working properly. To test the cooling fan, drive the car for at least 30 minutes so it is nice and hot. Shut off the engine and open the hood. With your hand try to spin the cooling fan. It should offer resistance to the movement, and only spin about half a revolution. If it keeps spinning without much resistance, your cooling fan clutch is broken, and you must purchase a good unit, or install electric cooling fans. Also grasp the cooling fan and see if there is any free-play or wobbliness. If there is, it could break off causing much damage. Make sure to replace it.
4) If the car overheats at highway speeds and in stop-and-go driving, first step is to change the thermostat. You can test your unit, but they are so inexpensive that it makes sense just to purchase a new one. Many car parts stores carry a high-flow units. The factory temperature is 190F, but you can install a 180F unit without any problems.
5) Clean the radiator! If the radiator is the original Toyota unit, it is most likely internally clogged up. I would strongly suggest purchasing a new unit from the aftermarket vendors, they cost about 150 dollars. If you do not want to purchase a new unit at this time, remove the radiator and clean it inside and out by flushing with water. Many Supras collect lots of debris where it is not visible. See the picture at the end of this post, obtained from: http://www.supras.com/~riemer/sonictech/cooling/radairpluged.html
6) Purge any air from the coolant system. While air in the coolant will not make you automatically overheat, it can add to the problem. The most obvious sign of air in the system is a spiking temperature gauge, and "gurgling" noises coming from the dash area (heater core is located there). Unfortunately these are also signs of a BHG. The simplest way to purge most of the air is to start with a cold car and remove the radiator cap. Start the engine up, and let the car warm up. Keep adding coolant or water to the radiator neck while it's running. When the thermostat opens, you will see the coolant level drop, or lots of air bubbles come out. It helps if you rev up the engine to about 2000 RPM. When the coolant level is stable and the thermostat is open (look at the temperature gauge), put the radiator cap back on. Any remaining air will purge itself during driving, in a healthy system.
