This week, John Paul puts the “doctor” in Car Doctor, with a prescription you might not have thought of.
Q. I have a Ford pickup truck that four years ago I changed the thermostat and flushed out the radiator and when I put the truck back together it overheated. I had the truck towed to a local repair shop and they told me they needed to bleed the cooling system. Now I want to service the cooling system again. What is the procedure to bleed the cooling system after replacing the coolant and thermostat?
Once you have completed the repairs, fill the radiator through the degas (overflow) bottle until the coolant level is between the level marks.
Run the engine at idle and fill the bottle to the upper coolant level mark.
Stop the engine and allow it to cool and refill the cooling system. Repeat these steps until the air from the heater is hot and the coolant level is stabilized.
You may need to do this 4/5 times until the coolant is full and all the air is out of the system. This is necessary to remove the air pocket that is trapped between the radiator and thermostat.
Years ago I learned a simple trick that sometimes works. When installing the thermostat, wedge an aspirin in it so that it holds the thermostat spring open. This will allow the coolant to flow and eliminate the air pocket.
Once the aspirin dissolves the cooling system should perform normally. This is not a Ford approved tip but one that has worked for me.