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First attempt to change coolant

Hello folks,

I tried to change coolant of my 2006 Sentra for the first time. The cooling system capacity of my car is 1 3/4 gallon.

I opened radiator drain plug and drained the radiator and the reservoir. The total amount of liquid that drained was a little over a gallon. I started the car and revved a bit but nothing really came out. I refilled about a gallon of distilled water (less than what came out) and ran the car for just a couple of minutes and the heat dial went to half position (standard operating temperature I notice during regular driving). It never goes that fast and that means there is a lot of air in the system. I tried to burp by pressing upper and lower radiator hoses. Some air did come out, but I assume not much.

I plan to drain this water in the evening (once the car cools down) and refill with the coolant. How do I make sure that all liquid comes out? Can I rev the car when I am draining the liquid? What happens if the heat dial goes up or can I let the dial go up to the operating temperature while draining the liquid?
(The engine block has a drain plug but it is not easily accessible so I can not really open that to drain rest of the liquid.)

What is the sure shot way of removing all air from the system, other than burping?

Thanks a lot in advance.

(P.S. - As I said, this is my first attempt and I am little panicked.)

Start your car and run it for about ten minutes with the heater on full blast. Check temperature gauge while you are waiting and shut the engine off in the event it goes into the “red”.

Let the car cool down and check the fluid level again. Add more coolant if needed and repeat the whole thing until the fluid level remains constant.

I hope you are using coolant and not only distilled water and make sure you fill the overflow reservoir to the marked level.

My DIY method has been to not ‘flush’ the cooling system with a garden hose (which is one way some people use to get all coolant out). But if you want to do it this way, I will leave it to others to coach you.

I buy extra jugs of distilled water and do a stepwise dilution as a way to ‘flush’. Using your system (1 and 3/4 gallon, or 7 quarts total) as the example and saying only 1 gallon (4 quarts) drains at a time:

  1. On the first drain, replace with one gallon of distilled water, leaving 3/7 quarts (or abut 43%) of the old coolant inside.
  2. Start the engine with the heat on (or use the car for a day or so with heater on at least some of the time) to circulate and mix the water and old coolant.
  3. On the second drain, replace with one gallon of distilled water again, leaving about 18%% of the original old coolant inside. Repeat step 2).
  4. On the 3rd drain, replace with one gallon of distilled water again, leaving about 8% of the original old coolant inside. Repeat step 2).
  5. On the 4th drain, replace with one gallon of distilled water again, leaving about 3% of the original old coolant inside. Repeat step 2).
  6. You get the picture of how the old coolant is diluted out and replaced by distilled water.

And the above example is slower than your actual situation because you said you are draining more than a gallon (4 quarts). If you are concerned about distilled water not protecting against corrosion, then do the above over the course of a day.

Once you’re satisfied with the level of old coolant left, add 3 1/2 quart of undiluted antifreeze (the kind that is diluted 50/50 for use) and top off with distilled water and you are done.

As for removing air, are you burping with engine running and radiator cap off? This way, as air comes out and space is created, you can add more water or coolant thru the radiator cap.


This is exactly why I have mine done at the dealer for $60.

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Vive la différence! :wink:

(Although I wonder how you know how much of the old coolant your dealer removes. Do you stay and watch what they do?)

An alternative way for @Noelm is to go with half the maintenance interval of the coolant system and just drain (without removing all of the old coolant) and refill with new coolant. No flushing of any kind needed (and much faster and less expensive than $60).

@Noelm In one of your other posts you stated you live in an apartment. Please tell us you did not just drain the coolant out on the ground. That stuff is poison to animals.


Easiest way to change all the coolant and make sure there’s no air trapped in the system is have a shop do a coolant exchange.

Here’s the machine I use.

You just connect it between the upper radiator hose and the radiator, fill it with a 50/50 mix of coolant, turn it on and in about 3 minutes all the coolant is changed.

No muss no fuss.


Yeah I used to do mine myself too but not anymore. How are you possibly going to know what your dilution is by adding water, then draining again, etc. It should be 50-50. You’ll need a tester to see what it is. I think at this point just follow Tester’s advice and have it done.

Is this the first time YOU are changing the coolant or the first time the coolant has been changes in this vehicle? It is supposed to be changed every 5 years.

If this is the first time it has been changed in this vehicle, then I would agree with @Tester on this one. But if it has been changed according to the maintenance schedule in the past, then you have already made your first mistake. As long as the coolant has never been allowed to be fully depleted, then you should drain and refill with a coolant mix, typically 50/50 antifreeze and distilled water.

The reason you only got one gallon out is that the block and the heater core have some coolant in them. There is a block drain usually located somewhere near the oil filter, but you should get a maintenance manual for your vehicle to find the exact location. You might also look at to see if they show the location on their website. BTW, if you have the SER or Spec V model, you have an Altiima motor instead of a Sentra motor.

Your motor may have a bleed valve, usually located in the gooseneck where the upper radiator hose connects to the motor. Again, look this up before you try anything.

Now, because you used distilled water, you have not done any damage, just made your task a little more difficult, maybe. If you drain the radiator and the block this time, then just use a premix to refill and you will be OK. If you choose to just drain the radiator, you can refill with a premix, but your total concentration will be a little weak (35%). Not a problem if you don’t live in an area that gets below freezing in winter, and plan on doing your next coolant change in three years instead of five.

Right now you have about 1.5 qts antifreeze in a total of 7 qts mix. If you only drain the radiator, you will be left with about 0.64 qts. So add 3 qts of full strength antifreeze to the radiator and top off with distilled water and you will be good to go.

You could also put the full gallon of antifreeze in and end up with a concentration of about 65% antifreeze. This will give you a little more corrosion protection and protect the engine down to about -50 degrees F. This concentration give the lowest freeze point and the highest boiling point, however it has less thermal capacity so it is not recommended of you plan on doing much highway speed driving in temps above 100 degrees F.

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Our wastewater plant says you can dump the old coolant down the toilet, check with your treatment plant, I do not know about septic systems. The city also provides coolant and oil recycling centers, storm drains typically found along streets are a no no for coolant ~ antifreeze.

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Humans are also animals. Most apartment complexes I am familiar with have kids who could also be attracted to the sweet smelling “Kool-Aid”.

The Chevron SERVICE station where I worked (1971-72) had a similar machine. Fast and effective, At $60 every 3 years I can more than justify this service at the dealership. They also check hoses, radiator cap, and perform a pressure test.

@Waterbuff, Actually, your method is excellent and it gives you EXACT idea of how much you are replacing. Thank you. I will follow the method (at least try to).

@VOLVO_V70, No I didn’t spill even a drop on the ground. I am very well aware of ethylene glycol.

@keith Thats the real issue. I got this car pre-owned and I didn’t get any maintenance history with it. Since I have acquired it, I don’t remember paying for coolant change. Quite often, got ‘topped the required fluids’ at the time of oil change. This is my first car and had absolutely no idea how I should be maintaining it. A couple of years ago, I got Forester and then everything dawned on me after I read through all documentation. Since then, trying to do as much as I can.
I searched about the bleeder valve but on Sentra forums, there is a conflict on where folks suggesting bleeder valve to be. Since my knowledge is limited, I didn’t want to screw up further.

I don’t know where you folks live but $60 coolant change is a great deal for us NYCers. I was quoted $139. If its complicated then I would pay, not an issue, but from the videos I saw on YouTube, it seemed relatively easy to do. Until this year, I paid religiously for every car work and would still pay but $95/hr labor adds up on a car that isn’t even worth $3000.

I suggest you open the owners’s manual, read the maintenance schedule and maintain your car, according to the “severe service” guidelines

Thats exactly what I started following since last year

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I understand the distilled water, back when I was young and ignorant, I could only drain out 1/2 the 3 gallons of coolant fluid, so I would do the hose flush, figuring it was all water after, and add 1.5 gallons of concentrate, ended up with the perfect mix. Remembering do not add cold fluids to a hot engine not running or risk cracking a block. Wondering if that is the reason for the 50/50 mix

Did you ever see what those animals do to each other? :see_no_evil: :hear_no_evil: :speak_no_evil:

It sounds like you are on the right track there OP. A couple of suggestions, not a good idea to start and run the engine when the radiator is bone dry. There must always be at least water in the radiator, at least half full or more, all the time the engine is running. Otherwise you’ll be sucking air fromt he radiator which will form pockets inside the cooling system , including possibly damaging the engine.

Most diy’er don’t remove the drain plugs to drain the engine, at least I don’t. We diy’er just drain the radiator. And so we do the work-around of doing the drain and refill several times to clean the system of the old coolant. I think Waterbuff above suggests that idea too. Suggest to follow that advice. With the engine cold, and heater set to max, drain the radiator, refill with water or coolant, leave the radiator cap off and run the engine for 5 minutes, let it cool, then drain the radiator again. Then do the final fill.

For most cars this all works better if you drive the front wheels up on ramps first. That puts the top of the radiator at the highest point in the system, so air bubbles that form will just leave through the hole where the radiator cap is removed.

Remember: Only run the engine when the radiator is full or nearly full.

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@GeorgeSanJose Just to make sure I understood correctly, put the car on the ramps while adding water/coolant (after draining the radiator), right?

It looks like I have already trapped some air during the previous water addition. I am following Waterbuff’s method and I am on the second cleaning step. After adding water this time, I idled the car for abt 15 minutes with the fan full and heat max, and there was very little hot air. I assume this is because of air getting locked inside. As the car started heating to the operating temperature, the water started overflowing the radiator. Is that because the air trying to escape?

I will try to follow all suggestions tomorrow and report what I notice.

Thanks for commenting.

If the block drain is easy to get to, there’s no reason for a diy’er to not remove it and drain the block

At home, I drain the radiator and the block, and then I refill a 50-50 mixture ONCE. And I leave it alone, until the next service, in about 5 years time

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