Bing makes a good point:
“ If you have not serviced the timing belt I suggest you just have that done at a dealer to preserve the engine. The kit comes with the belt, water pump, and tensioners.”
Plus, coolant is toxic, old coolant must be disposed of correctly.
Have a pro do it. If the radiator hoses are original, I would have them replaced at the same time.
Except on the 90s Ford trucks I’ve seen. The thermostat is closed and the air is trapped in the engine unless I remove a heater hose to let the air out when refilling.
B.S.
Tester
The engine wouldn’t fill after draining the coolant unless I disconnected a hose to let air out on two Ford trucks I worked on. Was this not the correct method Tester? Was something else wrong like a clogged vent?
I’ve owned/serviced Ford cooling systems over many years. And have never had to remove hose anywhere to fill the cooling system.
The only difficulty I’ve found when doing so is eliminating the air out of the heater core after filling the cooling system. Especially on the vans.
Tester
Muddy brown could just be coolant that has never been changed and has turned to sludge. You might also have a lot of rust in it. Even after a good flush, cooling systems like this might make new coolant look pretty nasty after a short while, then you might drain and refill at the next oil change.
Muddy means that the corrosion inhibitors have been used up and the coolant is eating your engine. Replacing it is now critical. The best thing to do is to take it to a professional with a coolant flush or coolant exchange machine. This will not be cheap and in your case, you could be charged more because it may take two complete flushes. BTW, as several here will attest, I do NOT normally recommend any kind of flush.
If you still want to do it DIY, there is a reasonable alternative. I have cleared out two cooling systems that had reached this condition. Neither had started to overheat or leak yet but they probably weren’t far from it. If you have an automatic transmission, then your transmission may be being damaged as well.
First, get one of these kits
Drain the radiator and the block. The block drain is just a plug, usually square top, and located near the oil filter. After it is fully drained, close the petcock on the radiator and replace the block plug.
Refill with premix or make your own premix with concentrate and distilled water. I usually go a little rich doing this, up to 2:1 antifreeze:water. Use the kit to insure that all the air is removed from the system.
Drive for a week or so. If the coolant is clear (colored but clear, like colored celophane), then just keep an eye on it. At the first sign of cloudiness, replace it again.
If you can’t drain the block, then just do the radiator, but remove the lower radiator hose from either the block or radiator, whichever is easier. In this case, drive for a week and then do a drain and fill again regardless of how the coolant looks.
In my opinion factory coolant is best, but any universal coolant can be used especially on an older vehicle. The factory formulas are tuned to the mix of alloys used in the system, but all the universals are adequate for any engine, as long as you replace the coolant a little more often. The coolant marked Asian, US, and European are a little closer to the specific factory formulas so if they are the same price, then why not.
I am still opposed to using any chemicals other than the antifreeze in the cooling system.
Keep an eye on your transmission fluid color. There is a heat exchanger inside your radiator for the transmission and if it develops a leak, the coolant will get into the transmission and that will really harm it.
In the old days we would change anti freeze every fall along with the thermostat. Never used the prestone fill kit but I made a hose dev,ice from an old garden sprayer and several diameter pvc glued together. Then I could insert it into the radiator hose and turn the water on. Kind of a mess.
Lately I had the coolant changed, thermostat, a couple hoses, and the crank sensor and it cost me $600. I thought the price was fair in these times but I think the coolant alone is approaching $30 a gallon. Just saying is all, people need to get paid for their time.
I did that on all my cars when I lived in Colorado. Just part of the pre-winter routine. Gives a good opportunity to make damn sure the coolant is freeze-proof to -20 deg F, absolutely necessary in that climate zone. A friend moved there from Calif, and I helped him do this on his car which still had Calif plates. He was complaining it was unnecessary as coolant was only 1 year old. Then 2 or 3 neighbors came by, saw the plates, and said the new Colorado resident was being very wise to do the fall cooling system service. Made me look good … lol …
Why would that change during the summer?
Vehicles sold in California have weak antifreeze? During assembly all vehicles receive the same coolant/antifreeze.
Well it is George speaking after all. He may be referring to an old Ford with no coolant recovery tank and may have been topping up the radiator with water half the year. 
Well maybe you young folks don’t remember when they came out with permanent antifreeze, and then long life or five year antifreeze. It normally doesn’t freeze during the summer so making sure you had protection against freezing in the winter was important. Then again it was also important to restore the lubrication properties and rust prevention properties of the coolant.
Two year antifreeze must be replaced annually, that seems like a reasonable policy.
Yep, remember it well. Antifreeze wore out very fast and needed replacement pretty much once a year. I recall checking antifreeze every fall with a hydrometer and ensuring it would survive -25 deg F or you’d surely regret skipping that maintenance.
The glycol in antifreeze doesn’t break down with time and use.
So, It will always protect from freezing or overheating if the proper mixture is maintained.
What does break down is the lubricants and rust inhibitors.
And that’s why the antifreeze is changed on a schedule based on the type of antifreeze used.
Tester
It was not uncommon back in the 60’s to change the antifreeze about every three years. They used to sell a product called “water pump lubricant and rust preventative”. You would add a can of this once a year. You also added a can to the fresh antifreeze.
People in mild climates would also run just water with a can of this stuff added once a year. I did that in my youth in So Cal, no freezing temps to worry about.
From what I’ve experienced and read about it, it does. I maintained my cars so know what went into it and when. Yet, testing showed it was degraded over time. I don’t know what changed to affect how long it lasts but it certainly lasts longer now than back then. Maybe less air contact, corrosion inhibitors and other additives more effective at reducing oxidation, maybe cooling jackets not exposing coolant to as high temps…don’t know but just know it degraded on freeze protection back then…
In general, coolants degrade over time as the ethylene glycol breaks down into primarily glycolic and formic acids. Degradation occurs more quickly in engines operating at higher temperatures or those that allow more air into cooling systems.