Is it Safe to Drive With Low Engine Coolant?

Question

I have a 2001 Chevy Malibu and have replaced the engine coolant in it twice in the last six months after the low coolant warning light came on, and the light has recently come on again. The climate is mild here so there's no risk of freezing, and I do keep an eye on the temperature gauge - it doesn't seem to go very far above 180 degrees F in steady-state, which is about 10 degrees above where it sits with full coolant.

Is it safe to continue driving with low coolant as long as I continue to watch the temperature gauge? If not, what are the potential risks involved?

Update:

About a week or so after my original post, I decided to refill the coolant reservoir yet again and hope for the best. Not 48 hours later, I was on my way up a hill and suddenly the temperature gauge spiked up to the red line. I immediately stopped driving and had my car towed to the nearest repair shop. Turns out the intake manifold gasket had failed which was causing the leak. Fortunately there was no damage to the engine, but unfortunately the manifold is apparently very inaccessible in the 2001 Malibu, requiring more time to replace it. $1600 and 24 hours later (which included a coolant flush and two oil changes, the first of which was to clear out coolant contamination), my car was running fine.

Answer 1

"Is it safe to continue driving with low coolant as long as I continue to watch the temperature gauge? "

No, the temp sensor reads coolant temperature, if the coolant gets low enough to be below the temp sensor, now the sensor is reading metal temperature of the area it is screwed into (usually cylinder head), by the time it reads too hot on the gauge the motor is toast.

I have made lots of money off of people doing this.

Answer 2

If you do not have any leaks, then your coolant is most likely getting burned and/or going into your oil. My guess is going to be a problem with your head gasket or some crack or warping in the head.

I believe coolant in oil used to turn oil more brown and make it more foamy or milky. These days, the detergents and dispersants in modern oil can reduce those appearance effects and can be harder to spot visually. You might be able to smell the sweet antifreeze smell in the oil.
Water in oil usually will end up evaporating out of the pcv. Glycol in oil will not boil away like water and will form acids and affect your oil. This wears out your oil and can cause sludge buildup and corrosion in the engine.

Low coolant will cause overheating and can cause stress on the water pump. Low coolant that is topped off can cause overheating due to trapped air in the system. Any overheating can cause cracks or warping.

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Personally, I would probably just keep driving it until it dies completely, as long as I dont really care about the engine that much and plan on buying another car afterwards.
I would also be doing the following:

Instead of relying on the low coolant warning or the temperature gauge to see how your coolant level is doing, "proactively" check your coolant at least once a month (or like every week) and top it off. Of course still keep an eye on the temperature gauge in case of any issues.

You should also change your oil more often. If your normal usage of the vehicle is full of very short trips, then you need to change the oil even more often.

Although this ignores the source of your problems (whatever is allowing the coolant to leak), you can mitigate damages and prolong useful life of the vehicle.

Answer 3

First, you do need to find out where the coolant is going. There is UV dye that can help with this, and if your car is smoking, that could be a sign that the coolant is leaking into the engine rather than on the ground.

For the main question, "Is it safe", as long as you keep an eye on the temperature and it's not getting too high, you should be OK in the short term. The problem is that as you loose coolant, you also loose the ability to cool (sounds obvious, but worth saying). Then what happens when you get stuck in traffic on a hot day? Also, there will come a point when the coolant gets too low to properly circulate. Getting air into the system could severely affect the water pump's ability to circulate, then things heat up quickly. This could leave you stranded, and could also lead to engine damage.

I would recommend adding coolant as soon as the light comes on. The warning light is there just for that purpose - to let you know you really should add some coolant before it starts to get too low. Keeping a jug of coolant in the trunk doesn't seem like a insurmountable issue, so do that and add a little when needed.

Answer 4

Its not good to run with low coolant, even worse to run with no coolant. Actually it can be quite disastrous (possibilities include blown head gaskets, seized pistons and a number of expensive repairs), but many times this is a result of a leaky radiator cap which is easy (and cheap) to replace.

Someone already mentioned the dyes for detecting leaks, but you can usually tell if it is the radiator cap just by opening the hood after a long drive (if you can't see it, you can feel it - just be careful not to burn your self)

Try replacing the radiator cap and just in case keep a gallon of distilled water to top it off as needed (add corresponding amount of antifreeze when you get home). As a bonus, you'll have a source of water in case something does happen and you need to take a long walk :)

Don't just monitor the temperature gauge, check the coolant level when possible until you figure out the approximate leak rate. Do you need to top it off daily, weekly or monthly? If it gets to daily and replacing the cap doesn't fix it, you'll have to look for a leak (to weld, patch or otherwise repair) or replace the radiator (typically < $100 at various online shops) Fortunately since it is imperative that the radiator gets good air flow, it is one of the easiest parts to get to and usually relatively simple to replace (If you can change your own oil, you can probably replace the radiator).

Don't jump the gun and put leak repair in the coolant, it may fix the leak, but its repeated use can build up and reduce the cooling capacity of the radiator.

Answer 5

If you can't see any obvious signs of leaks, or steam coming from anywhere if you run the engine, a likely cause is a cracked cylinder head gasket, which is letting the coolant into the cylinders and out of the tail pipe as steam. That could soon cause a lot more damage than the hassle carrying a water container in the car to top up the radiator.

Personal story to back up what @Moab said: I once had a radiator blow while driving. The coolant temperature sensor didn't move. (The car didn't have a coolant level sensor). The first I knew of the problem was when I put the car out of gear to stop at a crossroads, and the engine immediately stopped and seized solid. Fixing that meant a complete new set of conrods and pistons, as well as a new radiator!

Answer 6

You need to get this car to a Mechanic ASAP. Even though you keep an eye on the gauge. By the time the gauge is in the danger zone the damage has already been done. Spent the bucks now to fix it and save a bundle on the chance that thing Blows a gasket..........