QUESTION: I know little about cars and have a general question. I have a '96 Geo Tracker and with the temps here below 0 lately (I live in Colorado too) any my Tracker having to sit outside 24/7, I wondered about my anti-freeze. The manual says to check the level in the plastic coolant reservoir and keep it between the 'low' and 'full' marks and not to add any directly to the radiator itself. If the coolant in the jug is where it should be, does that mean I have enough antifreeze? And if I took it somewhere to check for the temperature threshold and it it's not as low as it could or should be, say -25 degrees, is it necessary to drain and flush it or could they just add coolant? Thanks
ANSWER: If the anti freeze isn't old - yeah, you can just add until the concentration is correct.
The level in the reservoir and the anti freeze concentration level are two separate things.
If the level in the bottle is ok, that's good. If the bottle is empty (you should be consistent and check it when the engine is cold), and the engine is cold, it's ok to add directly to the radiator. Don't remove the radiator cap when the engine is hot (if you can't put your hand on the top of the engine, and leave it there, the engine is hot), there's a very real chance of being badly scalded by boiling coolant.
The coolant concentration percentage is normally about 50-50 antifreeze and water (good to about -35f). If you live somewhere the temp can be expected to drop below -30, a mix of 60% antifreeze and 40% water (good to about -65f) can be used.
Antifreeze is also an anti-corrosive, and usually begins to have reduced anti-corrosion protection after about three or four years. Flushing is usually not necessary if the anti freeze is green(some brands are blue or pink) and doesn't look like a creek or river at flood stage, and there aren't a bunch of deposits visible on the top inside of the radiator (cold, remember?) Flushing is usually not necessary more often than every 5-7 years at the most often, and is frequently sold more for additional profit rather than as a necessity. To be fair to the shop, most of them have no idea how long the coolant has been in your vehicle's cooling system, and a flush and change eliminates one possible problem for the customer for a number of years, as well as allowing them to look at the drive belts, hoses, water pump and radiator for additional problems that might become an issue in the near future.
There's equipment/systems out there that can filter the old coolant, remove evil chemical impurities, and restore the ph level and the anti corrosion chemical package(right now it's only applicable to green (ethylene glycol) coolant). I've used a couple different systems , and have found that reconditioned coolant seems to have a 50%-75% longer life before test strips show it's getting old again.
Another thing nobody says anything about is that while 50-50 anti freeze does raise the boiling point of the mixture to about 235F, pure anti freeze only carries about 55% of the heat that 50-50 carries, so it would be highly likely that an over-concentration would cause overheating on days above 75f. Additionally, pure anti freeze is enough thicker than a mixture that it exacerbates a tendency to overheat.
Anti freeze protection level testers (freeze point)are available for less than $10 lots of places. There are also PH test strips on the market that will tell when anti freeze is getting chemically old and should be changed. It's a good idea to replace the radiator cap when changing the coolant every few years. (they do lose their ability to hold pressure with age, and the pressure raises the boiling point of the mixture and helps reduce boil over).
A note - there is no such thing as "permanent" anti freeze. That's an advertising scam. The "permanent" stuff is 5 year instead of 2 year anti freeze.
---------- FOLLOW-UP ----------
QUESTION: Thanks for all the info. If the level in the bottle is ok but want to increase the concentration for more protection, would adding more anti freeze to the bottle work, or would I need to add it to the radiator?
I suggest this procedure, which, although a little time consuming will allow you to set the protection level accurately.
Get a pan that will hold a couple of gallons(can be used for oil changes later)and a funnel that will fit the radiator opening on top.
With the engine cold, open the drain at the bottom of the radiator, and drain the coolant into the pan.(also drain the overflow bottle into the pan)
Then check the coolant concentration in the pan.
SLOWLY, a cup at a time add straight anti freeze to the coolant in the pan, stir it, and check the concentration until it's about where you want it, close the radiator drain, and, using the funnel, add the new cold mixture to the cold radiator. (I find it useful to pour the mixture into a less unwieldy container than the drain pan to avoid attempting to fill your pockets with antifreeze at the same time as the radiator)
When the radiator appears to be full, start the engine, and let it idle with the radiator cap off, the water pump will circulate the coolant and a few air bubbles will end up at the radiator.
Keep topping up the coolant in the radiator and allow it to idle until the area of the engine where the top radiator hose connects to the engine is too hot to touch - then re-install the radiator cap, and allow the engine to idle until the gauge indicates operating temperature. Sometimes, it will appear to overheat - no big deal - shut it off and let the engine cool (it cools faster with the hood up) until it's not too hot to touch, SLOWLY with canvas type gloves on and a couple of rags on the cap, remove the cap, and add new mixture as necessary and fill the bottle. Re-install the radiator cap and let it idle to operating temperature again. If everything seems normal take it for a short drive while watching the temp gauge. If you fill the overflow bottle to the top, the first time it gets hot any extra will go overboard, and after cooling, note what the level is for future reference. Sometimes it's necessary to repeat the "let it cool and add more" a couple of times - depending on the phase of the moon, the effectiveness of muttered imprecations, and whether the neighbor's dog barks during the procedure.