How to: Drain the Coolant

[The Mic]

Draining the Coolant

Be safe and start with a cool engine. Set the interior heater control lever to the HOT position. This will allow the heater core to drain. If you have a radiator overflow reservoir, then remove it and drain it as well. Now remove the radiator pressure cap and open the radiator drain c***. You can use a pair of pliers to reach a difficult-to-reach one or to free a stuck one, but be careful. Remember, the Nissan drain cocks are made of plastic, so they're easy to break!

If the drain c*** is really stuck, or broken off flush with the bottom of the radiator, then you can disconnect the lower radiator hose from the radiator to drain the coolant.

Let the used coolant drip into a container or pan. If your house has a city sewer disposal system, then you are allowed to empty your old anti-freeze into your drain. Don't just pour it on the ground or into a septic tank system. Better yet is to take it to one of the hazardous waste disposal facilities in your are, or you can nicely ask a auto repair shop to dispose of it.

Draining the radiator alone will only remove about half of the coolant. There is an engine drain plug located on the side of the block. Removing this will allow the remainder of the coolant to escape. It's messy, but it's the preferred way.

Refilling

First, tighten the drain cocks and any hoses you may have removed. Check on the side of the new container of antifreeze for how much antifreeze you actually need. Now most people just put the "standard" 50/50 (half water and half antifreeze) ratio back in their system, but I recommend using only as much antifreeze as necessary. The reason for this is the fact that water by itself is a much better conductor of heat than antifreeze!

It is generally recognized that straight water will cool a car more effectively than any combination of water and antifreeze, despite antifreezes marginal increase in boiling temps. So, the old adage of "if some is good, then more is better" does not apply with respect to antifreeze. There will still be plenty of anti-corrosion inhibitors and water pump lubricant even with a 20% ratio ofantifreeze.

What about using distilled water with the antifreeze instead of ordinary tap water? The reasoning here is that normal tap water has minerals dissolved in it. Through repeated heating in your car's cooling system, those minerals will eventually precipitate and form hard deposits in the radiator, especially in small passages. Distilled water is free of minerals, and therefore will not havethis effect.

However, now the reasoning is to use regular tap water because water normally likes to have ions floating around. If it doesn't, then it gets them from wherever it can. Aluminum readily ionizes, so the distilled water "steals" the ions from the aluminum components and they corrode. If you use tap water, it is "pre- ionized", so to speak. The tap water will sacrifice itself, and not your engine parts, to the chemical reactions created during thermalcycles of the fluid and metal parts.

The cooling system has nooks and crannies that can trap air. The filler neck is supposed to be at the high point to let air out, and there is a small hole in the thermostat to allow trapped air to escape.

Slowly pour the antifreeze and water into the radiator until it is full. Now you probably won't completely fill the system initially. Start the engine and let it idle until the thermostat begins to open. The water level in the radiator will invariably go down. Add some more water or antifreeze until it is full. Remember only add water to a hot engine while it is running! Better still is to warm the engine with the radiator cap on, let it cool and then check thefluid level. Check the fluid level periodically over the next several days.

Which Antifreeze To Use?

Most antifreeze is made with a colorless base chemical called ethylene glycol. A green dye is used in most brands, although there is a Nissan brand which is red. The latest entry into the market are the "long life" types of antifreeze which are tinted orange or bronze (e.g., Prestone Long Life 5/100, or 4/60). These are good for four to five years.

If you are changing from the "green stuff" over to one of the long life antifreezes, then you must thoroughly flush out your cooling system first. The corrosion inhibitors in the green and the orange/bronze antifreezes are not compatible. After you have removed the green antifreeze put back in only water. Let the water circulate. Let the engine cool and re-drain the water. Repeat this twice more.

It's a good idea to make sure that the antifreeze is a "low phosphate" type. The presence of phosphate in your coolant will force the concentration of aluminum ions to be extremely low. This will tend to increase the rate at which aluminum metal components of the engine will oxidize (corrode) into the coolant.

The aluminum phosphate formed will tend to collect in your cooling system and will NOT flush out. This could impair the efficiency of heat transfer and reduce water flow rates through the system.

So to be safe, use a phosphate free coolant. Read the label on the antifreeze container. If it says "phosphate free", it should be OK. If it says "safe for aluminum (I don't know which engine you have) engines", it should also be OK. If it doesn't make one of these claims, then find another variety.

What about the "pet-friendly" antifreezes? These use a base of propylene glycol and will do the same job as ethylene glycol. They cost a little more and require a greater quantity to provide the same protection and they're really only a bit less hazardous. Their real claim is that they don't have a "sweat" odor or taste (I wonder who found this out!) and therefore are less likely to attach pets or small children.
Modified by S13GUY at 12:11 PM 2/1/2005

[bcar240]

excellent writeups! We should make a 240 how-to forum just for these! I am sure we could find some others to go in there and more would come soon! Great work man!

edit: I seperated them by posting in this one. here are the others that I seehttp://www.nicoclub.com/zerothread?id=100769ht ... ?id=100766

[onosqv]

Draining the Coolant

However, now the reasoning is to use regular tap water because water normally likes to have ions floating around. If it doesn't, then it gets them from wherever it can. Aluminum readily ionizes, so the distilled water "steals" the ions from the aluminum components and they corrode. If you use tap water, it is "pre- ionized", so to speak. The tap water will sacrifice itself, and not your engine parts, to the chemical reactions created during thermalcycles of the fluid and metal parts.

Modified by S13GUY at 12:11 PM 2/1/2005

Aaaa, crap. I got a koyo aluminum radiator and put in distilled water. So I should be using tap water? That's what I get for trying to baby my baby . So tap water will work better than distilled I guess?

[gumby]

what about the little plug on top of the intake manifold? i thought that was the release pressure when you drain it.

i cant get my coolant plug outta the block

[sil80drifter]

block drain plug is as described under the exhaust manifold, hard to get to, but possible.

sil80

[BomexS13]

great write up! I can do this when I switch to Koyo.

[slipnfall]

Great write-up, thanks! Good timing, seeing as many of us are looking at a seasonal weather change soon. I make it a force of habbit to change every year... I use 60/40(h20/anti) in the summer and 40/60 in PA winters.

what about the little plug on top of the intake manifold? i thought that was the release pressure when you drain it.

No you don't wanna use that to release pressure(esp when hot): you'll have an old faithful with hot steam coolant spewing everywhere. Best way to release pressure is it to let it cool down, but if it's an emergency, a functioning rad cap should allow you to crack it open w/out the cap coming off(still may spew fluid, so you always use a wrag), but at least the majority will spray outward, not upwards..::edit:: I'm not reccomending ANYONE do it this way!!! I'v never been in a situation that I couldn't wait 15-20mins to allow a safe cool-down!!! ::edit::

Anyways, you should remove the rad cap to allow air into the system when draining: preventing a vacuum cond that may not allow all coolant to exit. When refilling, crack that little plug on the water jacket. Keep filling until you see a steady stream of coolant flowing out(ie no bubbles/irregularities). This'll help purge air out up to that point; the rad filler neck is higher, and has an air relief as the original poster mentioned. Don't know how effective it really is, but I do it by force-of-habit.

-Slip
Modified by slipnfall at 11:36 PM 2/8/2005

[Thrwnsprkz]

THANKS!Ill try that when i refill my coolant... it was overheating when i changed the themostat... so ill try that (i know theirs air in it)