Antifreeze question

[radionut98]

For NTX----, I have owned 4 new cars in my 66 years and have never changed

anti-freeze in any of them. Mostly 140,000 to 200,000 highway miles. The color

green/yellow seems never to change and I have never seen any corrosion in the

radiator neck. My present vehicle Chevy Astro Van has 161,000. Is it

really necessary to change at 50,000 or so? Am I hurting my system? I have

never had to change a hose. Thanks

[NTX5467]

The necessity to change has one main reason, which I discovered back in the middle '80s from a BASF/Saab coolant handout brochure. Ethylene Glycol is a natural enemy of the lead solder used in the radiator tanks and heater cores, therefore an additive package in the coolant has to be put in place to keep this from happening. Just as oil never wears out, the ethylene glycol probably doesn't either but when the additive package is depleted with time and age, that's when the problems start--probably not an overnight situation, but one that takes a while to happen. There is also an alkalinity "window" that is also realted to this situation, as I understand.

The Shell Rotella coolant I mentioned is rated to 600,000 miles in over-the-road diesel use and I also seem to recall that it has some additives to prevent cavitation around cylinder liners (possibly similar in concept to the "wetter water" additives?). At 300,000 miles, it will require a "booster shot" of a particular additive, which I suspect is for corrosion protection similar to the "corrosion inhibitors" we used to regularly see in the '60s. I do not know what materials are in those diesel cooling systems, but the way the Shell engineer talked in those Car & Driver columns, this coolant would be a better alternative than Dexcool by a long shot in a collector type vehicle that sees limited use. That was a few months back so you might want to check with your library people to find those articles, do your own research, and make your own decisions.

The green color is just a dye for identification and has no real bearing on coolant condition and/or protection other than to possibly indicate the degree of dilution of the coolant in the cooling system. Seems like some of the coolant brands in the '60s (maybe Zerex?) were blue or another unique color consistent with that particular brand?

The other issue on modern, computer controlled vehicles is that many sensors are positioned to contact coolant just as the temperature gauge sensor/sending unit do. If these sensors are "one wire" sensors, that means they ground through the coolant and then through the engine itself. If the conductivity of the coolant is "out of spec" it can cause these sensors (which obviously operate off of a voltage/resistance situation) to give false readings to the engine computer and could ultimately result in a hard to trace and fix driveability concern. Those driveability concerns also might affect whether or not the vehicle might pass an emissions test too as the fuel curve map would be shifted from the desired values. Now, it seems that more and more coolant temp sensors are "2 or more wire" sensors which means they either have more than one circuit they feed or they now ground through the ECM.

I suspect that as the miles on your vehicles were almost exlusively highway miles, that means the engine was up to operating temperature for longer periods of time. Just as with motor oil, that operation could result in all of the "bad" things not happening as they would in more short trip/city driving where the engine sees more heat transitions per day.

For example, GM is now putting Engine Oil Life Monitors on many of their vehicles. It turns on the Change Oil light dependent on how the vehicle is operated. On the new Trailblazer with the new inline 6 cylinder engine, the cooling system was upgraded so much that an engine oil cooler is not needed even for severe trailer activity. That plus the aluminum engine castings result in the computer not turning on the Change Oil light for up to 15,000 miles if the conditions are right (according to GM's research) or it can turn it on in as little as 3000 miles in a cold climate with many short trips.

On the vehicles which have the later style composite radiators and heater cores, which your Astro van could well have, there is no lead solder in the system. BUT the radiator and heater cores and some piping are aluminum so that protection will need to be maintained to prevent corrosion.

From my own experiences, looking down through the filler neck of a radiator migth not be the best judge of condition on crossflow radiators (with side tanks instead of top/bottom tanks). What can look decent on the top could drastically change as you progress toward the bottom core area--to the extent that the bottom is plugged with sediment and settled out silicates that can't be seen from above.

As always, highway miles are still the easiest on the vehicle. The more consistent temperatures mean that fluids stay hotter so any condensate contamination (and related chemical issues) is cooked out with use or minimized. Therefore, if they don't break down, their lifespan is extended.

Even though the temperature gauge might be in the center, it takes about 10 miles in moderate temperatures for the axles and other powertrain components to get up to THEIR operating temperatures. The longer they stay in those temperature ranges the better for the fluids and lube. Normal engine oil and automatic transmission fluid start becoming compromised past 270 degrees F. with some brands going up to about 300 degrees prior to their integrity being compromised.

Hope this might help explain some of those concerns for you.

Enjoy!

NTX5467

[radionut98]

Okay NTX----, sounds (looks) like you answered my question pretty throroughly

so if I keep the Astro for another year I suppose (since I'M turning it over

to the XYL (Ex young Lady) I had better get the system flushed and new coolant

put in it since she will be doing mostly short haul trips. Thanks again

really appreciate it. Loren

[Guest]

To my understanding, the coolant should be replaced every year, because it will gradually become acidic, and eventually start attacking the metal (all metals, not just lead)

Jyrki

[NTX5467]

Agreed, it will attack all metals, but the softer metal in the core plugs and the lead will be the first to go. I think current coolants now state they can be used for up to two years as they probably have improved additive packagaes to keep the corrosion and such under control--best to read their recommendations on the jug they come it. It did used to be recommended to do it yearly in prior times and that would not be a bad thing to do as a default mode action.

Enjoy!

NTX5467

[Guest]

1973 Chevy bought new in 74, 88 ford ranger pic-up bought early 1989, 89 Chevy impala, all still in service and in MY posession. 80 dodge pic-up ran 12 years, among many others over the years i have owned and treated with brutal punishment in ambient temps from -20F to 104F. NEVER changed antifreeze from what the factory put in. Among these only the 73 chevy required a radiator replacement about 10 years ago and 1 welch plug about the same time. Poured the original antifreeze back in and its STILL in there discounting what ever needs to be added on rare occasions of about a cup or so once a year and maybe not that often. Same goes for ATF, manual trans and rear axle grease. OF course this does not apply to unusual conditions such as floods or people who go fishing thru streams in their vehicles.

THE IMPORTANT thing is to check these (especialy the anitfreeze) at least twice a year for level fullness AND USE A HYDROMETER TO CHECK THE COOLANT!.

Radiators will only last a certain length of time no matter what u do or dont do. About 10-15 years is their limit.

Basicly, the risk factor of NOT changing is so damn low that its NOT worth the effort.

[NTX5467]

I am pleased that you have had such exceptional service from those vehicles. It tends to prove that American vehicles are not the "poor excuses" that many seem to perceive they are.

I wish you well in your ventures,

NTX5467

[Guest]

it is difficult to compare FULL size (or LARGE) American cars to small (or at least smallER) foreign cars relative service or anything else.

[Guest]

BTW. The secret is to keep the ENGINE oil changed every 3K miles or sooner depending on service demands and to DO YOUR OWN WORK!!!.