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Old 10-14-2011, 11:27 AM   #1
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Question How long does antifreeze really last?

I admit I have committed a cardinal sin by having my coolant in my car longer than the usual "2-year replacement interval." From what I remember, the water pump was last changed in early 2006 since it started leaking. I am due for a timing belt and water pump again next year (5-years and 30,000 miles), but don't know whether I should change the antifreeze out now to be safe, or wait until early spring of next year.

The antifreeze used in '06 was Prestone and the bottle said '5-year' on it. However, how long does the modernized silicate/phosphate free antifreeze really last today?
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Old 10-14-2011, 11:36 AM   #2
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I think you should change it every 6 months for the next two years to make up for your lack of maintenance. This will insure you flush out all of the old coolant and get back on track with the change intervals.

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Old 10-14-2011, 12:05 PM   #3
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Yes yes I know. I should be penalized

This green stuff apparently said 5-years on the bottle. It can mix with any color anti-freeze too. I'll see if I can drain it out this weekend. Sadly, my block plugs are seized AND stripped. I can only drain by pulling the radiator hoses.
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Old 10-14-2011, 12:15 PM   #4
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The thing that "goes bad" in coolant is the anti-corrosive ingredients. By nature they are susceptible to oxidization. The oxygen in the system combined with the heat cycles oxidizes them. 5 years is the maximum recommended time before those chemical become ineffective in preventing corrosion. The most common problem caused by not refreshing coolant is water pump failure.

The anti-corrosion is also the reason you should use distilled water instead of tap water if adding water to the cooling system. The minerals in tap water add fuel to the corrosion process.
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Old 10-14-2011, 12:16 PM   #5
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What about the volume in the block that I can't extract? Can I just fill through the radiator hoses and the reservoir for the rest of this motor's life? I understand that the new coolant will mix with the old still, which I am not too happy about.
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Old 10-14-2011, 12:17 PM   #6
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Cooling aside, I think you want to know is the antifreeze protecting the engine against corrosion. I'd check it with a test strip. In addition to checking the freeze-point, they also determine if the antifreeze has become corrosive. Personally, after doing the heads a couple years ago, I'm a big believer in flushing the engine every 2 years. Just too many variables: mixed formula, how many times topped off, heat/usage, tap/distiled water, etc.

BTW - the heads on my block drain bolts were stripped on my 84 too; I bought a set of craftsman bolt extractors (like an ease-out) and they came right out.
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Old 10-14-2011, 12:47 PM   #7
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You are correct. My biggest concern is if the antifreeze is starting to corrode. Since I can only drain the coolant via the radiator, I will do it that way and just fill. Two years later, I will repeat the process and make sure I keep up on maintaining the cooling system. Dang wedding prep is deterring my mind from other important things.
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Old 10-14-2011, 04:17 PM   #8
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Well you can use fresh water from a hose inserted into the rad, but without looking at the diagram I'm not sure how you know it is going past the termostat and into the block, thus pushing out the old stuff. You would know when it ran clear, but . ...unless you used gallons of distilled, you would have plain H20 in the block.

So the best thing is to repair the drains; I have not done this, but I read here that a properly sized Time-sert is a fix for stripped drain plugs. That would be the best and return them to function. Would probly need some sealer or JB Weld. YMMV.
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Old 10-14-2011, 04:17 PM
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