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Discussion Starter #1 (Edited)

I. General

There are two basic ways to change the coolant. One is the “quick and dirty” method used by most dealerships, that’s good enough for the average Joe. The other is a much more thorough way to do it if you really care about the longevity of your expensive engine.


II. Quick and dirty.

This is the way most dealers would change the coolant. I wouldn’t do mine that way, so this part will be only the basic steps of how to DIY without much detail. Also, if you are changing from green to gold or extended life coolant (ELC), DO NOT use this method, but use the more thorough method explained in the last section below.

Your objective is to drain everything out of your cooling system, so there is nothing left in there except a little of the old coolant that won’t drain. Then refill with pre-mixed 50/50 antifreeze.

The cooling system holds about 7 gallons total. About 5 gallons will drain from the radiator drain valve. Another half-gallon will drain from each block plug. And a cupful or so will drain when you remove the lower radiator hose. But that last gallon is in the heater core and won't drain.

A. Get prepared. You’ll need at least 6 gallons and maybe 7 gallons of 50/50 pre-mixed coolant.

About 6 gallons of the old coolant will drain out of the radiator drain valve, the lower radiator hose, and the two block plugs. So you need a couple of 5-gallon buckets to drain it. You may also need a pair of ramps to raise the front end a little if the drain buckets won’t fit under the drain valve.

B. Drain.

1. Remove the pressure cap, then open the radiator drain valve and let the old coolant collect in the bucket. Stop the flow before the bucket runs over. Then use the second bucket and finish draining the radiator.
2. Disconnect the bottom radiator hose from the bottom of the radiator. This will allow some more old coolant and maybe some gunk to drain out into your bucket.
3. Remove both block drain plugs from the block and let them drain into your bucket.
4. Properly dispose of the old coolant. In most jurisdictions you can pour it down the toilet.
5. Connect the bottom radiator hose, replace the block plugs, and close the radiator drain valve.

When you finish draining, there will be nothing left in the system except about a gallon of the old 50/50 mix of antifreeze and water. So if you add 50/50 mix, you'll maintain the 50/50 ratio.

C. Refill. Pour the 50/50 mix into the degas bottle. You’ll probably not get much more than 5 gallons in at first. Run the engine until the thermostat opens, then you can probably add a bit more. Drive it for a few short trips and you can probably get in some more. At around the 6 gallon point your system will be full. You may have to open that seventh gallon, but you won’t use much of it. Hang onto it for future use.

Quick and dirty with a twist:

After draining as much old coolant as will drain, fill the radiator (and degas bottle) with water, set the heater control to high heat, then run the engine until the thermostat opens. Then run the engine a little longer to flush the heater core. Then drain the radiator and both block plugs. Do that at least two cycles to dilute the old coolent left in the heater core.

But now you have water instead of 50/50 coolant in the heater core, so you cannot use 50/50 antifreeze to refill. Instead, pour in 4 gallons of concentrate antifreeze, then top off with water.


III. Thorough Method, Coolant change procedures – ’99-up 7.3L Power Stroke Diesel engine

The problem with the quick and dirty method explained above is when you get done you’ll have about 6 gallons of new coolant mixed with one gallon of old coolant. By following the procedures below, you’ll have all new coolant in there after you finish the procedures.

Your objective is to drain everything out of your cooling system, then flush it with water, so there is nothing left in there except distilled water when you pour in the antifreeze. But because there will be water in the system before you pour in the new antifreeze, you have to use concentrate antifreeze instead of the pre-mixed 50/50 mixture.

(Prices mentioned below are in November, 2008, in the USA, and do not include tax)

  • Get ready.

    Go to the store and buy 4 gallons of antifreeze concentrate. I bought Motorcraft Premium Gold antifreeze concentrate: $15.40 per gallon = $61.60 for 4 gallons. Do not buy the 50/50 mix.

    Go to Wal-mart and buy distilled water. 20 gallons if you want an excellent job of flushing with distilled water. 16 gallons if you want an adequate job. 11 gallons if you want to do a so-so job. In November, 2008 it cost me $0.64 per gallon, so total cost $12.80 for 20 gallons. Wal-Mart had it in cartons of three one-gallon jugs for convenience, so I bought 7 cartons = 21 gallons for $13.44.

    Go to my auto parts store and buy a coolant filter replacement element for my aftermarket coolant filter system. $10.98.

    If you don’t already have a cooling system flush kit installed, then go to almost any auto parts store that sells Prestone antifreeze and buy a Prestone flush kit. It’s only a few bucks. If you already have one installed, then you must find the remaining parts that were not left installed on the truck. Mainly, that’s a double female hose adapter. If you can’t find the Prestone version in your barn or garage, you can make one with a short piece of garden hose and two female hose connectors. Or just go to the store and buy a new Prestone flush kit to get that part you can’t find. ;)

    If it’s been more than 3 years since you’ve replaced them, then you might also want to replace the following parts. Prices are from my Ford dealer in Nov 2008, and include a 20 percent discount from list price. These part numbers fit my ’99.5, but I suspect they will fit all ’99-up 7.3L PSDs.

    Lower radiator hose: part number YC3Z 8286 CE, $27.61
    Upper radiator hose that goes around the fan belt instead of through it: F81Z 8260 CA, $24.54
    Thermostat: F6TZ 8575 EA, $32.48
    Thermostat housing: F81Z 8592 AA, $23.18
    Pressure cap: F6DZ 8100 A, $6.90

    I use the Ford parts, but if you replace the stock 195º thermostat, know that you can buy a 203º thermostat from Dieselsite for around $36. If you replace the thermostat housing, know that you can buy a nice billet aluminum housing for about $47 from that same outfit.
    DIESELSITE Products

    Tools needed include:

    - A large pair of “water pump” or Channel Lock pliers for removing the radiator hoses.
    - A 3/8th or 1/4th inch ratchet with 6” plus 3” extension and an 8mm socket to remove the bolts that hold down the thermostat housing.
    - A 5-gallon bucket. If the bucket won’t fit under the radiator drain valve and still have room to open and close the valve, then I’ll also need a pair of ramps to raise the front of the truck a bit.
    - A kiddy wading pool about 4 or 5 feet diameter and several inches deep.
    - Something to dip the water out of the kiddy pool and into the 5-gallon bucket - maybe a 2-quart saucepan?
    - A garden hose that will reach from the faucet into the engine compartment of your truck.
    - A clear glass canning jar or clear water glass.
    - A funnel for pouring gallon jugs of liquid onto the Degas bottle.
    -If you must haul the used antifreeze to somewhere other than your bathroom to pour it down the toilet, then you'll need a bunch of empty one-gallon milk jugs or water jugs. (Most jurisdictions allow you to pour used coolant down the toilet.) Remember that after you get done, you'll probably have 19 empty distilled water jugs and 4 empty antifreeze jugs, so maybe count on using those to recycle the used coolant.

  • Drain

    Remove the pressure cap from the Degas bottle.

    Drain the radiator into the 5-gallon bucket. Stop it from draining at about 3 or four gallons and empty the bucket by properly disposing of the used antifreeze. Then finish draining the radiator. You should get a total of about 5 gallons out of the radiator drain valve.

    If you have one, remove the coolant filter element and dispose of it. If you have a shut-off valve on the coolant line, be sure you leave it open so the lines will flush.

    Place the kiddy pool under the front of the truck to catch any leaks and drains.

    Remove the upper radiator hose from the thermostat housing (this is a heck of a lot easier said than done!). Remove the thermostat housing. Remove the thermostat. Reinstall the old thermostat housing without the thermostat, but try to use the gasket from the old thermostat. Temporarily reinstall the old upper radiator hose onto the old thermostat housing. (If it’s a tight fit, you won’t need to also clamp it on.)

    Remove the lower radiator hose. (Expect a cupful or so of coolant to come gushing out when you disconnect the lower hose from the radiator.) Install the new lower radiator hose, but leave the end that connects to the radiator unclamped so you can easily remove it for each flush cycle.

    Install the flush “T” on a heater hose. Connect the garden hose to the “T” with the double-female hose adapter provided in the flush kit.

  • Flush with tap water.

    Set the heater controls to max heat, and the fan to high speed. If you have a manual valve to stop coolant from flowing through the heater, open that valve so the heater core will flush.

    Turn on the water to a low pressure but enough to run into the system faster than it drains out of the radiator drain valve. Too much pressure will damage the heater core. The water will begin draining from the valve.

    Watch the Degas bottle, and as soon as you see water begin to rise into the Degas bottle, crank the engine. Water will probably spray out of the space where you removed the thermostat, but that won’t hurt anything. Let the engine idle for a couple of minutes, then kill the engine. Turn off the water. Let the water drain from the drain valve (and maybe some from the coolant filter base). Disconnect the lower radiator hose from the radiator, then after it stops dripping, reconnect it.

    Dispose of the water in your catch basin (kiddy pool) and get ready for another cycle.

    Turn on the water and wait until the water begins to rise in the Degas bottle, then crank the engine. Let the engine idle for a couple of minutes, then kill the engine. Turn off the water. Let the water drain from the drain valve. As the water drains, catch a glassful and notice the color. If there is even a hint of color in the drain water, we need to flush it again with tap water from the garden hose. Disconnect the lower radiator hose from the radiator, then after it stops dripping, reconnect it.

    Dispose of the water in your catch basin and get ready for another cycle.

    After your drain water is nothing but clear water, then replace the kiddy pool with the 5-gallon bucket. Disconnect the garden hose and close the flush ”T”. Close the radiator drain valve. If you have an aftermarket coolant filter, install the new coolant filter element.

  • Flush with distilled water

    Pour in 4.5 gallons of distilled water. Crank the engine and let it idle for a couple of minutes. Kill the engine and drain the radiator. After it’s drained enough so you won’t get a bath when you disconnect the lower radiator hose from the radiator, then do that. After it has drained good, then reconnect the lower radiator hose.

    Repeat that last step one or two or three more times – depending on how good of a job you want to do of flushing out all the tap water. Two flushes will be 9 gallons total, three will require 13.5 gallons, and 4 times I do will require 18 gallons of distilled water. Plus you need another two gallons for the final fill. So you need to have on hand before you begin either 11 or 16, or 20 gallons of distilled water.

  • Button it up.

    Replace the thermostat, install the new thermostat housing, and then install the new upper radiator hose. Be sure the thermostat housing bolts are good and snug, and the hose clamp is moved down to its clamped position on the hose. If you dropped a bolt and it disappeared into the bowels of the area around the water pump, then go to the Ford house and buy another one. Expect to pay more than $5 each for those 15 cent bolts. (Don’t ask how I know this. :eek:) Finalize installation of the upper and lower radiator hoses by moving the clamps to the clamped position.

  • Filler up.

    Pour in 4 gallons of concentrate antifreeze. Top off with distilled water. Install the new radiator cap (pressure cap on the degas bottle).

    I just barely got the 20th gallon of distilled water open when mine was full. But after driving it to town a couple of times, some of the air bubbled out and it took a bit more. Hang on to that last partial gallon of distilled water for later additions.

    Finally, that job is done. And it should now be good for at least 50,000 more miles with no coolant maintenance.

    By using all 4 gallons of antifreeze, my concentration is about 57 percent antifreeze. That’s good enough for some very cold country.

  • Options I didn’t use.

    If you remove both block plugs as well as draining the radiator and lower radiator hose, the tap water flush should not require as many cycles to get all the color out of the system. But that is a PITA, so I didn’t even think about it. Without removing the block plugs, mine was clear water after two tap-water flush cycles.

    If you want the 50/50 mixture of antifreeze and distilled water most experts recommend, then pour in only 3.5 gallons of antifreeze instead of all 4 gallons. Then fill the half-empty gallon jug of left-over antifreeze with distilled water, and mark the jug "50/50". Then you’ll have topping-off mixture for future use.

    Some experts say you don't need to run the engine during the tap water flush cycles. But running the engine provides a little more safe water flow thorough the heater core, so I think it provides slightly better flushing action.

Premium Member
18,870 Posts
Discussion Starter #2 (Edited)
One thing that changed since I posted this thread a year ago: Ford now requires you to periodically test the gold coolant with the appropriate coolant test strips available at your Ford dealer. Most folks won't need to add supplemental coolant additive (SCA) before the 3 years/50,000 mile life of the gold coolant is over, but some may. I plan to test mine about once each oil change interval (OCI) from now on.

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What about just testing the coolant and adding the SCA if indicated w/out the changing procedures?

Premium Member
18,870 Posts
Discussion Starter #5 (Edited)
What about just testing the coolant and adding the SCA if indicated w/out the changing procedures?
Sorry, Matt, but I didn't see your question until today.

Both your PSDs came with gold coolant, so you don't need to change it . The procedures in this thread don't apply to your situation. So yeah, simply test the gold coolant every year or so and add SCA only if needed.

When you do change the coolant to fresh coolant, you can simply drain the radiator and refill with 50/50 gold coolant using the "average Joe" procedures. That will give you another 50,000 miles of driving before you need to change the coolant again. But of course you could also use the "prefectionist" procedures to do it right.

Gooch's procedures are basically the same as mine - flush it good with distilled water, then fill with antifreeze concentrate, then top off with distilled water. The big differences are he advises using antifreeze that has not been approved by Ford, and he insists on draining the block plugs every flush cycle instead of making that optional. But if you use gold antifreeze and distilled water, then the final results of both procedures will be identical.
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