# B Percentage of antifreeze in cooling system

1. Jul 15, 2016

### HRG

Our 2002 Toyota Sienna's cooling system capacity is 10 quarts (no heater). Using radiator petcock, 5.7 quarts of coolant is drained. Recommended mixture is 50/50 antifreeze and distilled water, which is what it is now before the replacement starts.

Drain-1: Refill with distilled water only. Run engine till thermostat opens + 10 minutes.
Drain-2: Refill with distilled water only. Run engine till thermostat opens + 10 minutes.
Drain-3: Refill with 1 gallon of undiluted antifreeze and 1.7 qts of distilled water.

What will the percentage of antifreeze end up being? Please show the step-by-step calculations so I can learn how to do it. Thanks.

2. Jul 15, 2016

### Staff: Mentor

At the start, the cooling system contains 5 qts. of water and 5 qts. of pure antifreeze. If you drain 5.7 qts., how much liquid remains in the system? Of that liquid, how much is pure water and how much is pure antifreeze?
Continue this analysis at each step.

BTW, is this a homework problem, or is this a question about your actual car?

Last edited: Jul 15, 2016
3. Jul 15, 2016

### HRG

This is my actual car.

I'm a senior citizen and way past going to school.... I'm just hoping someone will do the calculations and show me how to do it. This senior citizen never had a lot of brain power and doesn't have much of that little left in the tank... With sample calculations, I'll be able to do them if the amount of fluid drained is different or if I do an additional cycle of drain and refill. Thanks.

Last edited by a moderator: Jul 15, 2016
4. Jul 15, 2016

### Staff: Mentor

First drain/refill:
Starting with 5 qts of water and 5 qts of antifreeze, if you drain 5.7 qts of liquid, 4.3 qts will remain. Even though the water and antifreeze are mixed, for the purpose of the problem, you can imagine that they are separated. Of the 4.3 qts of coolant, 2.15 qts are water and 2.15 qts are antifreeze.

If you refill the radiator with 5.7 qts of water, there will now by 5.7 + 2.15 = 7.85 qts of water and 2.15 qts of antifreeze. In this step, you've gone from a 50% mix of antifreeze and water to 21.5%.

Can you continue this analysis for the second and third drain/refill steps?

5. Jul 16, 2016

### HRG

I calculate the final mix as 44% of antifreeze. Is that what you get?

6. Jul 16, 2016

### HRG

Modifying my flush as follows:

Drain-1: Refill with distilled water only. Run engine till thermostat opens + 10 minutes.
............ The mix is 21.5% antifreeze.

Drain-2: After draining 5.7 qts of coolant, the remaining 4.3 qts are at a 21.5% antifreeze mix.
............ So 21.5% of 4.3 qts remaining = .93 qt is antifreeze.
............ Adding 1 gallon (4 qts) of antifreeze = 4.93 qts of antifreeze.
............ 4.93 qts / 10 qts total = .493 = 49.3% antifreeze.

In other words, doing 2 drains and refilling with 1 gallon antifreeze and topping off with distilled water will end up with a 49.3% antifreeze mix. Is this correct?

If correct and I since I already bought one gallon of antifreeze, then the above will end up close to the recommended 50/50 antifreeze mix. I might do the coolant flush this way since my existing coolant looks pretty red and good.

7. Jul 18, 2016

### HRG

To anyone:

I need to do the van's coolant flush shortly. Are my calculations correct?
If not, please post step-by-step calculations so I can learn how to do it.

Thanks.

8. Jul 19, 2016

### Lord Crc

Looks good to me.

9. Jul 20, 2016

### HRG

Thanks for your confirmation. I'm going to go ahead and do the coolant flush.

If anyone sees that my calculations are incorrect, please let me know so I can do it correctly next time.
HRG

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