I know absolutely NOTHING about cars, other than to get the oil changed, keep the tires rotated, and check the oil and tire pressure occasionally. Other than that, I rely on a mechanic for all my car needs. That being said...

I have a 1999 Blazer. I'm low on engine coolant, and I usually just put water in it, but I've been wondering lately if that was right or not. What is that used for, and is water an acceptable coolant? Thanks for all the help and I'm enjoying browsing the forums and learning.

 

Water is an acceptable coolant for a moderate climate where temperatures do not drop below freezing or climb too high (greater than ~100*F). Antifreeze serves to lower the freezing point of the coolant as well as raise the boiling point. If the concentration of antifreeze to water is not appropriate for your climate, you could have the system freeze up or boil over, depending on the conditions. Either of which could cause permanent damage to your engine.

A 50/50 mix of antifreeze & water is typically used. At this concentration, most antifreeze will lower the freezing point to ~-35*F and raise the boiling point to ~265*F down/up from 0*F/235*F for 100% water.

As far as coolants go, that is a hot topic. Unless you have had the cooling system flushed, make sure to top off with a coolant that is compatible with GM's Dexcool. If mixed, non-compatible coolants can degrade the service life of Dexcool, leading to problems.

Another important thing to note is that tap water (what comes out of your faucet in your house) has quite a few minerals and other elements that do not necessarily get along well in a cooling system. I use distilled or deionized water (whatever I grab first off the shelf) when servicing cooling systems.

That said, I would recommend a cooling system drain & refill using 2 gallons of concentrated long life anti-freeze that is Dexcool compatible, then a top off of distilled water (<2 gallons required to top it back off). This should get you near the 50/50 mark and give you the longest service life for your cooling system. While you have the system drained, replace the thermostat & radiator cap. I prefer the Stant Safe-T-Cap for the radiator and have never been let down by Stant Super-stats (the more expensive one available). Both are relatively inexpensive and easy to change out while you have the system drained.