Changing antifreeze

[Tom Vanco]

I have a question that I can’t seem to find an answer to on changing antifreeze.

I know how to drain it and I know you can run water through the system and drain again. The reason to do this is to “flush” all the old antifreeze out of the system. Then the general advice is to then add 50/50 antifreeze back in the system. Okay, BUT, what about the water that is still in the engine block? If I add a 50/50 mix I will no longer have that mixture after it is mixed with the water in the block.

I don’t feel right about just drain and refill because I will still have old worn coolant in the system diluting the new coolant. I don’t want that.

So how do I get the water out of the block so I can do a 50/50 mix. I can’t get to the engine block drain to open it.

Thanks for any info you can share.

Topic

[Ken]

You can get a hydrometer to check the specific gravity of your mixture and ensure it’s appropriate for your climate.

http://www.amazon.com/ATD-Tools-1105-Antifreeze-Coolant/dp/B00AZ9ZZZ6/ref=pd_sim_263_2?ie=UTF8&refRID=15M4ZS2Q7170AZC59TK4

[Mike]

Compressed air with a blowgun that has a rubber tip that can seal against a coolant hose (A rag wrapped around a standard blowgun tip works) is your solution. That is my trick I use every time I flush a cooling system with a hose. You really need to take the thermostat out to get full complete circulation of your hose water, but doing it both at a heater core hose and a radiator hose is a pretty good alternative. On the other hand if you can’t get compressed air, you can still get most water out by blowing the excess water out manually (with your lungs and mouth). Then just use a 60-75% solution to fill it with, so that the remaining water doesn’t dilute it below 50%.

[Mike]

Your drain should be at the lowest point of the system, usually the bottom of the radiator. If there isn’t a factory drain cock there, you can drain the system by removing the lower rad hose from the rad.

Draining from the lowest point ensures you’re draining the block too. I wouldn’t worry about the small amount of residual water remaining in the system. It’s the same as an oil change, you never get 100% of the old oil out.

If you really are concerned about residual water diluting your antifreeze mixture, you could always refill with a 60/40 coolant mixture to compensate.

[J]

The partial answer to your question is that some engine blocks have a block drain plug.

An example is the R18’s on 8th Civics. The service manual even tells you to remove it when changing coolant. When I changed my coolant though I didn’t mess with it because I didn’t have HondaBond on hand and they want you to put some on before you re-install the plug, I just accepted that I was mixing old coolant with new.

Useless information: On the R18 that hole for the block drain is also used for the optional OEM block warmer that Honda sells (it threads in place of the drain plug), pretty convenient.

[Cameron]

[quote=”tvak” post=138138]I have a question that I can’t seem to find an answer to on changing antifreeze.

I know how to drain it and I know you can run water through the system and drain again. The reason to do this is to “flush” all the old antifreeze out of the system. Then the general advice is to then add 50/50 antifreeze back in the system. Okay, BUT, what about the water that is still in the engine block? If I add a 50/50 mix I will no longer have that mixture after it is mixed with the water in the block.

I don’t feel right about just drain and refill because I will still have old worn coolant in the system diluting the new coolant. I don’t want that.

So how do I get the water out of the block so I can do a 50/50 mix. I can’t get to the engine block drain to open it.

Thanks for any info you can share.[/quote]

Yes you are correct, you do nor want to over dilute the coolant concentrate. But you do not have to worry about the fresh water still left in the system because you are going to add the correct volume of coolant concentrate so you end up with a perfect 50/50 mix.

1. You need to know the manufacturer’s spec on the cooling system capacity. It is stipulated in the owner’s manual normally or you can possibly find it on line through your vehicle forum (always double check though) or ring the dealership as a last resort or to verify.

2. If your car’s stated cooling capacity takes , say, 12 quarts then the main issue for you is to ensure you pour 6 quarts of the undiluted coolant concentrate into the system , ie 50%, because the only fluid currently left in the drained and flushed system is a bit of clean water. Take your 6 quarts of coolant concentrate and dilute it just a little, say, 2 quarts of your demineralised or distilled water (do not use tap water) and pour that all into the system at once. Then to complete the fill use your demineralised/distilled water and the end result will be an exact 50/50 water and coolant concentrate mix in the system if it is a 12 quart capacity system. It is that simple. No need to worry about getting any residual fresh water out of the system, such as the engine block, after the flushing. That is the advantage of buying the concentrate rather than the ready to fill, already diluted, 50/50 type product.

Just ensure you know the correct cooling system capacity for your vehicle and you cannot go wrong on the mix of coolant concentrate and water.

[Tom Vanco]

Hey thanks for the info! Some good tips there. Thanks again.

[Scott]

Wow. I was curious about the exact same thing before I flush the system on my 2012 Civic LX. Does anyone know if the HondaBond/liquid gasket/whatever is required for the 9th generation Civics? The only service schematic I have seen so far says to replace the existing metal/rubber gasket when removing the drain plug (not sure exactly what material it is made from but it is part number is 90401-PR4-000). But I would rather not crack open the drain plug on the block if I don’t have everything I need to reinstall it.

There’s no harm in going the extra mile by opening it up after draining the radiator, is there?

[Author]

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