1) The proper way to bleed the system is to have the car idling with the cap off, car's nose on an incline, ac/heat dial on full heat, and vent on high.
2) When the vehicle reaches the "R" in "NORMAL" the fan will kick on and the stock temp thermostat will be moving toward fully open shortly there after UNLESS there is an air bubble in the system. If an air bubble exists the stat will fail to open and the fan may fail to click on at the proper time because the pocket(s) of air are not what the sensors are built to measure. Thus, they will not ascertain the actual temp of the engine and overheating will occur.
3) If you have your vehicle as #1 describes and the coolant volcanoes out of the radiator then your problem (assuming parts are working properly) is an air pocket. You bleed this pocket out over the course of a few hours with the cap off. Trying to bleed it with the cap on through the degas bottle can get you a blown head gasket or worse.
Our cooling systems are a pain to bleed because the air can only move through the tiny hole at the top of the stat. Furthermore, the coolant entering the block at temps less than the stat opening have to share that same hole. This is the reason Ford engineers put a hole at the top of the stat; to allow transfer of air/fluid for bleeding purposes.
With the nose on an incline (because it puts the radiator at the highest point for the air bubbles to float to), watch the car and see if the fan comes on at the "R," and if the water begins to flow about the same time. The water flowing into the block will be indicated by a corresponding drop in the radiator. If this does not happen shut the car off immediately because it is not going to get any better (some over flowing will happen once shut off so have a catch pan or fat wallet ready). If all works well then keep the car running and continue pouring coolant as needed into the radiator (make sure the degas bottle is filled to the "HOT" level or a little higher). If the air pockets are gone, which is what proper functioning of the cooling system indicates then just let the vehicle cycle through a few times while checking the fluid (i.e., colder to "R," and back again). The vehicle will not overheat with the cap off so long as air pockets are gone and parts are working; the car is only idling this isn't hard to cool off. If the vehicle does not work properly...
4) After having shut the car off, fill the radiator up to the top (i.e., just before syphon hole to degas bottle). Wait 5-10 minutes. During this time, assuming the nose is up, small amounts of air will exit the block and small amounts of waters will enter it. At times you can even hear this happening (e.g., running water sound). After waiting fill the radiator up again, it may only be a small amount, but if it is burping, it will nonetheless require several small amounts of water. Keep doing this routine with the vehicle off until the fluid level does not change. When the fluid does not go down any further that is indicative of a proper air bleed down. Both the block and radiator will be full of fluid. At this point....
5) Return to step #1. Let the vehicle cycle at least two times to ensure proper fluid levels with nose up, cap off, vent on high, and heat on high. You may see a drop in fluid at this juncture because an air bubble could also be in the heater core (natural highest point on a level car). The heat and vent on high ensures that the coolant reaches and fills the heater core. When the air coming out of the vents goes from ambient to convection oven hot then you know that the heater core is purged of air. This will most likely cause a drop in radiator fluid levels since air has been evacuated and fluid has entered the core. Fill it up. Watch for two more cycles adding any necessary fluid. If all is well for those 2-3 cycles, congratulations! Your system is purged of the evil air pocket monster. Put the cap on and drive till your heart is content.
The degas bottle works up to a point, but one cannot hope to bleed their system of air for the first time after repairs through it. Follow these instructions I learned from a Ford 302 guru and your system will work perfectly the 1st time.
Thank you! This worked great. Did your steps a few times and I now have heat again. I really thought my heater core was bad... guess not! Went for a nice long drive and temperature didnt creep up on me anymore either
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