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Date:         Sun, 29 Apr 2001 11:39:11 -0500
Reply-To:     Joel Walker <jwalker17@earthlink.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Joel Walker <jwalker17@earthlink.net>
Organization: not likely
Subject:      Re: HELP Flashing red temp light!
Content-Type: text/plain; charset="iso-8859-1"

> Anecdotally, I've been told that certain coolant mixtures become acidic after > a year and should be changed annually. > Sounds like a good geeneric question for the list.

what i've learned from noising around and reading and talking to the tech folks is this:

antifreeze contains additives, just like motor oil contains additives. and just like motor oil, those additives get used up ... become depleted over time. some of the additives in antifreeze prevent corrosion. some of them lubricate the water pump. in about three years or 45,000-50,000 miles, those additives are just about used up. the tech folks at BASF (the folks who make the vw blue phosphate-free antifreeze. which is, according to them, the same stuff as the mercedes, porsche, toyota, audi, volvo, and saab antifreeze ... just different colors for each brand) tell me that the coolant NEEDS to be replaced every two years, to replenish those additives.

don't believe it? ok, go check on the 18-wheeler trucks. it seems they have the same problem, different solution: they have a filter on the coolant system. and on each side of the filter is a valve that they can shut off (so as to not lose much coolant when they remove the filter). the filter turns out to be sort of hollow, and in the hollow space, they put chemical additive sticks. so they can shut off the truck, turn the valves, yank the filter and put a new filter with new chemical additive sticks back on the truck, turn the valves again, and be back on the road in about 30 minutes. they don't have to wait for the truck to cool overnight like we do. why such a system? cause their antifreezes are 'guaranteed for 150,000 miles!" ... which is like six months of driving. and to wait eight hours for the coolant system to cool down before draining it costs them lots of money.

the point being that coolant, like any other fluid on an automobile or truck, NEEDS to be replaced. regularly.

the BASF folks also said that the phosphate-free requirement was only for areas that had hard/high-mineral-content water. with that type of water, there tend to be precipitates or deposits formed in the cooling system. possibly in the radiator, but certainly in the bottoms of the two plastic coolant tanks. at the very least, it 'looks bad' (according to BASF). they said any ethylene glycol antifreeze would work fine, IF you replaced it every two years. they were not very flattering of propylene glycol (possibly since i don't think they make an antifreeze with it), saying that it didn't handle the ranges of temperatures that ethylene glycol did. someone on the list said this wasn't true, but that less of the e.glycol was required (than the p.glycol) to reach those same extremes.

as i understand it, the coolant consists of antifreeze and water for a reason: - the water carries the heat away from the metal parts. water is better at this job than anything else they've come up with (that can be found cheaply and in most areas. i kinda doubt that any of us want to be riding around on top of a liquid sodium metal cooling system, like some of the early nuclear reactors).

but water freezes. and boils. so they add the antifreeze to lower the freezing point. it also raises the boiling point, and the engine becomes useful in most climates. a 50-50 (water to antifreeze) mix is considered normal. if your temperatures are extreme, either cold or hot, then the mix can be adjusted to 40-60 or even 30-70, but 30-70 is the most extreme case i've heard of in an automobile used for general purposes, in most places where humans live in cities.

the problem with all this is that you mix hot metal and water and you get rust. so something has to be added to prevent that rust ... and that's where the additives come in. once the additives are depleted, there's nothing to prevent the hot metal and water from forming rust.

unca joel


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