Discovering the cause of overheating can be frustrating. Here are some tips that can help you avoid this frustration.
Overheating After Engine Work: When you have drained the cooling system and especially after having the lower intake off or the heads or any other work where the block was drained, you may have a problem with the car overheating when you fill the radiator and start the car again. Nine times out of ten the cause is trapped air in the cooling system Often, the top of the radiator is not the highest point of the cooling system so air bubbles will get trapped in the engine. To avoid this, or minimize this, after you have filled the radiator, try to find a fitting on the engine that you can unscrew. On 94-95’s the perfect fitting is the ECT sensor it’s located on the heater tubes, on the front of the engine on the passenger’s side. Unscrew the sensor and slowly fill it, until coolant starts running out. Then screw the sensor back in. Leave the radiator cap off, put the heater control on full hot and start the motor. Some coolant will flow out, so have a pan ready. But after the thermostat opens in 4-5 minutes, the coolant level will drop drastically. Refill it to the top, put the radiator cap back on. Be sure the overflow tank is filled to maximum. Go inside the car with the engine running. If you are getting no heat out of the heater, there is still an air bubble, and the temp will soon skyrocket. Shut it down, let it cool and recheck the coolant level fill it if it needs it. Sometimes it really helps to drill a small hole in the thermostat housing and situate the hole at twelve o’clock this will help let the air pass. Often all it takes is a couple of refills, maybe even taking it out on the road and driving it around the block and letting it cool and refilling it.
Overheating on Vehicles with Electric Fans (94-95's and some others): Sometimes you will notice the car will overheat in traffic or idling, but not on the road. Here is something to try, after the car is starting to overheat, stop and see if the fan is running. If not, it’s time to start troubleshooting. First, leave the car running and turn on the air conditioner to maximum. If the fan IS running, then the ECT sensor needs to be replaced. It’s located on the heater tubes, on the front of the engine on the passenger’s side. Always use a Ford sensor, they are much more reliable. If the fan does NOT come on with the AC on then either the fan itself is faulty or the relay is bad. Most of the time the relay is located in the Constant Control Relay Module (CCRM) On 94-95’s the CCRM is located next to the coolant overflow reservoir. You can eliminate the fan as the problem by temporarily hot-wiring it with 12v to see if it runs. If it does not, than the fan is bad. If it does, the CCRM is bad. On 94-95’s there was a recall for faulty fan connectors. Look for a burned or melted connector. This was covered by a recall, but the recall has expired, so you’ll need to fix it yourself.
Here are a few other things to look for:
· Be sure your car still has the lower airdam in place if this is missing, airflow will be limited.
· Run a 180* thermostat this will be adequate in most cases.
· Use Water Wetter, it really works by reducing the surface tension of the water and allowing better heat transfer..
· Your radiator may be plugged, be sure it is clear of debris in the front, but the inner tubes may also be clogged. A good aftermarket radiator will cool better than stock.
· Be sure your lower radiator hose isn’t collapsing; sometimes they can delaminate and block coolant.
· Replace the thermostat, when they fail, they stick shut. Some aftermarket thermostats are designed to fail in the open position and they may not be a bad investment..
· If you did a head swap, the engine will overheat if the head gaskets were put in improperly.
Studies of the laminar airflow over hoods have shown that if you leave the rear of a cowl hood open, at speed air will be pushed into the engine compartment counteracting the air being pushed through the radiator. Contrary to popular belief leaving the cowl CLOSED will result in a cooler engine at high speed.