Rick already gave the straight dope answer. I’m just chiming in to warn about removing the radiator cap. Being female means you will heed the three foot high warning decals pasted all over the cooling system, but people do funny things when they’re worried or frustrated.
Check this chart:
It tells you freezing temp by % glycol vs water.
Change out the radiator fluid based on the interval suggested by your automaker.
Also, remember that your oil is in part low-temp capable due to chemical additives installed in the oil.
If your oil is really, really tired or contaminated, it might have turned from 5W30 to 10W30.
Asides:
I saw an anecdote by a tribologist about early-90s-vintage Castrol Syntec + Mobil 1 5W30 products turning into 15W40 when mixed, but I think that kind of problem is not a current going concern.
Also, many, “energy-conserving” thin 5W30 products turn into thick 5W20 products by the time you hit your oil change interval.
I’m just saying that the antifreeze already present for the AC would be enough to protect the engine at 25 degrees. My comment had nothing to do with operating the AC.
Inhibits corrosion is another biggy.
Even if you live in the perfect climate where it never gets below freezing or particulary warm you REALLY need “antifreeze” for the anti-corrosion aspect, particularly in modern cars…and it doesnt hurt to get it changed every so often.
I’ve heard of more than one person RUINING an engine by running a weak antifreeze solution or even straight water !
Oil changes and antifreeze changes are dirt cheap compared to car payments, even minor repair bills, or gawd forbid the early demise by even a few months of a car that would have lasted longer with the slightest bit of tlc.
I’ve lived in cold places my whole life, and I don’t do a damn thing different in the winter than in the summer. It’s really nice to have a garage to put your car in for the winter months, but that has everything to do with MY comfort, not the car’s - I don’t have to brush snow off or be miserable for that first ten minutes before the car heats up if it’s in the garage overnight.
Oh, don’t worry - it’s because I’m a girl that after I called my boyfriend to ask him if he knew anything about the stuff in the radiator that I called him back to say, “Now, you DO remember that you DON’T open that radiator cap when the car’s been running, right? Right?”
The disconnect here is that antifreeze isn’t present for the A/C. Antifreeze is in the engine’s cooling system to reduce the chance of the coolant freezing, boiling away, or causing corrosion. It’s there whether the car has A/C or not. Essentially, its presence has nothing to do with the A/C.
Zsofia, you can get a little tester which tells you what temperature your antifreeze mixture is good for. You test some of the mixture and the thing shows “-10” for example.
Hubby went around and checked all of our vehicles & tractors with his the other night, just to be sure.
I wouldn’t depend upon freeze plugs to save an engine block. I’ve seen them with all the plugs pushed out and still cracked. YMMV.
So there’s no possibility that running the AC may cause the engine to overheat?
In addition to inhibiting corrosion, anti-freeze serves as a biocide to prevent alge blooms if the car is not operated for long periods (getting it hot regularly will prevent alge)
“…engines have ‘freeze plugs’. These are plugs in the engine block designed to pop out if the liquid freezes…”
Not to be a nitpicker, but the “freeze” plugs are actually core plugs, and are installed to plug the gates where the molten metal was introduced when the engine block was cast. They MAY give some freezing protection, but not to the small channels in the block. BTW–from the factory they are steel, and highly susceptible to corrosion. The replacements are brass/bronze and are more resistant.
Just keep your coolant in the proper concentration, and flush the system every two years or so. There is NO lifetime coolant! Also, never mix different types of coolant. Some are green, and some are orange; they are different.
A short anecdote: Many years ago I had a plug rust out on a '64 Chevy. The leaking plug was behind the motor mount (some are in the back next to the transmission!). I had to jack up the engine, disconnect the motor mounts and remove them. Then wrench out the damaged plug, and drive in a new brass plug. About four hours work, for a fifty-cent plug! I did both sides.
:rolleyes:
Engines create heat when they burn fuel. they create a lot of heat. As you increase the load on the engine even more heat is created, and must be dealt with by the cooling system. Turning on the AC system imposes a load on the system. Will that load be enough to cause the car to overheat? That depends on a bunch of factors.
Can running the AC on a car with no antifreeze in the cooling system, cause it to overheat? Maybe, maybe not. It would depend on several factors including the design of the system, and condition of all the various components. Bad pressure cap? Might cause to overheat when with a good cap it might not. Internally plugged radiator, externally dirty radiator, a radiator that is not large enough, a poor design with crappy airflow, and the condition of the fan or fans could also maybe cause an overheating condition if run with just water instead of a mixture of antifreeze and water.
Ambient temp, and how the car is driven are also a huge factors. Going up a steep hill at 80 mph in 84F degree weather can easily cause overheating, while driving on level ground at 50 mph in 104F degree weather the car might be just fine.
I would also point out that the above factors could also cause a car with antifreeze to overheat in some cases. in other cases it would not.
The bottom line here is just because a car has AC there is no guarantee that there is antifreeze in the cooling system.
I have been in the business long enough to recall cars that had AC and didn’t have antifreeze in the cooling system. So get off my lawn!
To pick even more nits, there are engines nowadays that don’t have freeze / core plugs in the block.
BTW accessible freeze plugs never rust out. It is one of the immutable laws of the universe.
Well, it’s possible. Running the A/C puts more heat load on the engine. It won’t cause overheating if everything’s in good order, but if some cooling system components are faulty or marginal, then using the A/C could make the difference between overheating or not.
I’m not sure if we’re on the same wavelength here, though. It seems to me you’re saying that antifreeze is used in the engine coolant because the car has A/C, to which I’m responding no, antifreeze is used regardless of the car having A/C or not having it. I can’t imagine any car sold in the U.S. over the last several decades, with or without A/C, left the factory without antifreeze.
Am I failing to understand something?
And lots of people, particularly in warm climates, add water and only water when the coolant level is low. Good mechanics may do it right, but folks who top their own at the gas station every 9 months whether it needs it or not are gonna use what they have on hand: water.
So when the car was new the correct 50/50 or whatever mixture as installed. Over the next 10 years in the Carolinas, perhaps 5 gallons of water has been added & the coolant is now 97 (or whatever) % water.
Zsofia’s question was not “In a world of ideal auto maintenance, would my coolant be good for 20F overnight”, but rather, “Given that I have no knowledge of the coolant maintenance history of a 15 year old car kept in a warm climate, is it guaranteed to survive a 20F night?”
The answer to that question is: “Its not guaranteed to either survive or to not.” If you’re down to pure water, you are runnning a risk of permanent damage from overnight freezing if you don’t run the car a few minutes to heat it up prior to bed time. OTOH, if it has been maintained by a dealer or quality shop & you’ve been paying for coolant fills all along, then it’s completely safe, just like it was when it was new.
Only the OP can say where in that spectrum her reality lies.
Zsofia, for the record, I don’t do anything special to my vehicles in the winter that I don’t do in the summer, until the temp gets colder than about -20c (-4f), at which point I plug in the block heater (in the explorer… my Civic doesn’t have one, and I rarely use the Civic when it’s that cold)
S^G
Your car will also be happier if parked in a warmish garage on a cold night - not because the engine block might crack, but because an engine running on cold oil will experience an awful lot of wear and tear until that oil warms up.
It’s not going to kill the car, but it might shorten its lifespan.
A few additional thoughts. Many cooling systems have an overflow reservoir. It is under the hood of your car, and often looks like another windshield washer fluid container. Except, this one will have a thin hose running to it from the radiator. When your car is running (and the engine hot), the coolant expands in volume and the excess will be pushed out into this reservoir. When it gets cooler, the extra is sucked back into the cooling system (kind of like a straw). There are usually high and low marks on the reservoir (the lower one is often marked as “full cold” and the higher one is often marked as “full hot”). This is where you should check your coolant – do not open the radiator cap if your car has been running in the last hour, as there is a chance you could be burned by escaping steam.
The tester mentioned in post #29 works by sucking the coolant mixture into the clear middle portion, and the needle “floats” to a given location based on the specific gravity (i.e. the viscosity or thickness) of your coolant – water mixture. (The black thing on top is a squeeze balloon – kind of like the top of a turkey baster.) Think of coolant as similar to liquid laundry soap in thickness, and when you mix it with water it gets thinner. The thinner the mixture, the lower the anti-freeze protection. Thus, if the mixture is really thin, the needle will sink far to the bottom, letting you know there is little cold protection.
If you don’t have a tester, or don’t want to buy one, then look at the color of the fluid in the reservoir. If it is at least mildly green, you have some antifreeze protection. The darker the green, the greater the protection (most antifreeze is green). It is easier to see the color in the reservoir, as they are frequently made of white plastic. It is virtually impossible to see the color when looking directly into the radiator (remember – it is also dangerous to open the radiator cap on a recently running car). If you don’t have any fluid in the reservoir, try running the car for 10 minutes and then check it again. If you still don’t have any fluid in the reservoir, check your car’s manual, as you may have to add water + coolant.
Also, coolant won’t kill you if you touch it, but it is poisonous if swallowed.
I hope this helps, and that you get warm soon :).
And another note.
Coolant is BOTH poisonous AND tastes pretty good too, nice and sweet. Or at least used to, havent tasted any lately.
Do NOT leave it out for even a short time where small children, dogs, cats, birds, or thirsty alchoholics can get to it !
Bolt that was a good post.
And those testers are pretty darn cheap as well and quite handy. One other point about em. When you are testing the water/coolant, make sure the little swinging needle things doesnt have any air bubbles stuck on it when you take the reading. If there are any, you can usually dislodge them by thumping the tester fast and hard with your finger.
Also, if its an older car with an unknown history. It would be a good idea to go ahead and change out the coolant, and maybe a flush as well. Make sure you get the right type of coolant for that particular make/model of car.