Changing Ford Explorer Coolant
Draining and Flushing Anti-Freeze

Contributed by drbob

Planning on changing the thermostat while the system is drained? Of course you are!

Open the drain valve at the bottom of the radiator and drain the old coolant into a bucket. Take the old coolant to your local recycling center. Remove the thermostat and replace the water outlet. It's OK to just install the two easy bolts for this. Then, remove the radiator end of the lower hose, and loosen the water pump end so you can turn the hose up from the pump. Start the garden hose into the end of that lower hose so the water falls down into the water pump, and is clear of the fan and the belt. Start the motor, and let the water pump through the engine and heater core for a while, until it comes out clean enough to drink. Stop the engine, stop the hose, and let the water drain out of the radiator completely before installing the new lower hose. The new thermostat goes in now (vent hole on top), with the new top hose. You'll see that the heater hose connection is a little easier to get to with the top hose and thermostat housing out of the way, so replace the heater hoses before you do the top hose and 'stat.

With everything buttoned up, add a gallon (or less) of extended life coolant. A 40% mix is my target, so a gallon is about right if you save some for the overflow bottle. I like the Prestone because it's phosphate and silicate free (kinder to the aluminum and the water pump) and it lasts five years. I'm also a big fan of Redline's Water Wetter cooling system additive, especially after towing the boats and sitting around idling in 120+ temps in Arizona. Add a bottle (about $7 at Pep Boys) to the coolant mix, and top off the system with clean water. I use distilled water in the P-car to help the aluminum block, but I don't have a great way to get all the flush water out of the Explorer block so it gets the hose. On the coolant concentration, 40% protects down to about -15f, quite a bit colder than it gets in Los Angeles. Follow the instructions on the coolant bottle, keeping in mind that coolant actually inhibits heat transfer somewhat. Use the least you can, especially if you use the Water Wetter. WW has pump lubricants in it so you don't need much coolant.

Be sure to burp all the air out of the cooling system. Very Important! Then top up the coolant reservoir with a little coolant and water, and you are on your way.

Radiator Flush: Most use some kind of caustic solution to help with the cleaning process. Downside is that it's tough to get all the flush chemical out when you are done. It seems to gather around the o-rings that seal the radiator tanks to the core, and eventually it may cause enough corrosion to allow a leak at that seal. So, if your system is dirty and underperforming, use the chemicals, but do your best to get all of it out before you seal the system up again. With luck, you won't need to look at this job again for another five years.


Contributed by Chris R.

I must admit, I have done this for years, and can not say if it has effected my engine(s) either way, but I got to thinking. Reading Dr. Bobs article on changing the coolant I realized this is the worst way we could do this. Burping an engine, allows a large are of the water jacket to be filled with air and then when the thermostat opens, the air is replaced with water.

Now what is so wrong with this is the large amount of air allows no coolant to be in the upper portion of the engine. This also allows no water to be in contact with the thermostat, except on the radiator side meaning the engine has to overheat before the thermostat will open since there is no water to transfer heat from the engine to it.

I've started using a drain cleaner bulb (put it on the end of the hose and it swells up) to fill the engine's water jacket completely before starting the vehicle.




Updated September 18, 2001

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