I don't understand how to flush/refill... | Ford Explorer - Ford Ranger Forums - Serious Explorations
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I don't understand how to flush/refill...

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Well-Known Member
June 29, 2015
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City, State
Clearwater, Florida
Year, Model & Trim Level
2005 Ford Explorer XLT
I'm growing a little upset trying to figure out a clear answer to doing a radiator flush. I've posted this before but I just can't get the thoroughness that a newcomer needs to do this. Although I am mechanically inclined and determined to get stuff done, I must stress the fact that I started working on cars less than a month ago when I bought my first used '92 Explorer, so all of this is NEW NEW NEW.

Natenkiki linked me to a great thread (http://www.explorerforum.com/forums/showthread.php?t=251416) which is very thorough and explains basically everything you would "think" I need to know... but there's simply not enough answers in that thread for me to tackle this project right away.

Here's what I got out of it...


First, you drain the radiator using the petcock valve... this will (hopefully) get out any fluids you have in the radiator, BUT IT WILL LEAVE THE FLUIDS THAT ARE IN THE ENGINE BLOCK UNTOUCHED.

Therefore, a flush is required to get the fluid in the block...

So firstly, I am told to disconnect the overflow tank for this whole process... easy enough.

To flush, I have a Prestone Flush "T" on the heater hose... I am just supposed to take the radiator cap off and connect my garden hose to this "T" and let water run through everything and out of the radiator neck until it runs clear...

Since the thermostat will be closed and therefore blocking water entry, I am supposed to turn on the truck and even rev it a few times to heat it up faster... this will eventually open the thermostat and allow the water through--doing a nice full flush.

During this process, I can put the radiator cap back on which will create a closed system...except for the drain hole at the bottom of the radiator which I have left open. When it's good and clean, the water coming out of the drain hole should be clear and steady...

Now my flush is complete! I can put the drain plug back in and the overflow tank hose back on.



After all this... that means my system is now full of garden hose water. Who's to say how much?? How could anyone know??

The guy at AutoZone told me to do a flush and then fill it with 1 gallon of pure antifreeze and 1 gallon of distilled water... then drive it around and top it off with 50/50 pre-mixed when needed.

But maybe he didn't take into account that there would be a bunch of garden hose water still in the block?

A gallon of pure antifreeze wouldn't even fit into the overflow tank! So where do I pour it?

Also, if I pour a gallon of pure antifreeze in, and then a gallon of distilled water... I'd have like 40% antifreeze, 30% distilled and 30% tap in my system or something crazy...

I want a good 'ol 50/50 mix...

What do I need to do?

Please explain this to me as if I am a moron... because I just can't seem to grasp this whole flush thing..

Thank you <3

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Blue Bomb!
November 3, 2013
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North Idaho
Year, Model & Trim Level
1991 & 1994 Explorers
See your other thread for my response but just an FYI, the engine itself doesn't hold a ton of coolant. The water jackets are maybe 1/2-3/4" wide, the ports going up to the head are between a pencil and AA battery in diameter. There's more vertical storage in the engine than flat horizontal storage so once the block drains, there won't be but a cup or two at most in the block. If you fill a dry overflow tank up to the COLD mark with straight coolant, chances are good that compared to the straight water in the block, you'll maintain a 50/50 mix or even be slightly higher in coolant. Honestly, you'll be so close at that point, I wouldn't worry about it. Top it off with straight coolant.

Having pulled the engine out of my Explorer, when it was tipped, coolant would pour out but throwing a pile of shop towels on the ground soaked it up. It's not like there's a gallon sitting in the engine.

You're stressing way too much. Aim for a 50/50 but while filling it, in your mind, go heavy on the straight coolant.


Well-Known Member
March 1, 2015
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1992 Explorer XLT 4x4
i have read that thread too. it is very thorough. doing maintenance on a car is not something you can just go out and do right away. its trial and error. trust me, my 92 ex is my third car, and i am learning new things everyday.

as far as flushing goes, here is how i would go about it.

first things first, take the radiator cap off so the coolant will drain faster. then you need to pull the drain plug on the bottom of the radiator and let all the old coolant drain out. next is where you take the garden hose and put it in the top of the radiator and let it run for a few minutes to flush the radiator. dont put the drain plug back in yet, that will allow the hose water and all the gunk in the radiator to flow out. after that is done, you can hook up the garden hose to the flush tee and backflush the heater core. again, leave the drain plug out. after a few min of backflushing, you can now put the drain plug back in.
as far as refilling coolant goes, you will want to check the capacity for your radiator to make sure you have enough. you can add the pure and distilled water combo first. personally, i would spend the little extra money and just get the premixed stuff. just pour and done. using a radiator funnel, fill it up about halfway up the funnel. now for the burping. this is the tricky bit, cuz if you dont get all the air out you can end up having temp gauge issues. first, gently squeeze the upper radiator hose to force some of the air out. as you squeeze, the coolant should bubble down. as it does, add a little more coolant to the funnel. now, go ahead and start the engine and let it warm up. once the thermostat opens, you should see the level in the funnel start to go down and bubble as the air gets out. once the bubbling stops, pull the funnel and put the cap on quickly.
all done.


Elite Explorer
April 3, 2009
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Kailua-Oahu, Hawaii
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'05 Sport Trac XLS (RWD)
Prestone® Antifreeze/Coolant Tester
It is important to maintain your antifreeze/coolant at the proper concentration to provide good corrosion protection as well as prevent freeze-ups and boil-overs. This tester provides a quick and easy method to safely collect a sample and measure coolant concentration. It also allows a visual inspection of the antifreeze while you test it. This is a low-cost way to check the condition of the antifreeze/coolant in your vehicle.


Elite Ranger
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Elite Explorer
July 14, 1999
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Omao, Kauai
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'93 Ranger XLT 4X4
Closing this thread to keep the discussion in your other thread.

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