I just went through a cooling nightmare with my car so I've been paying very close attention to the coolant temp and what it should be running. When the car is moving the temp should be around 199-205 at normal highway speeds. At an idle 212 is the highest mine will get. Since I had all of the work done recently the car refuses to go over 212 even in triple digit temps with the AC running.

 

Disagree. I go through filters on my fridge every 2 months, that are supposed to be 6 month filters. My water is horrible & I would not even think about putting it in my car’s cooling system.

 

distilled is aggressive and will attack the metals in the engine/pump/radiator. For the amount of water needed tap is best. We can disagree.

 

Distilled water is stripped of its minerals. If i recall correctly, as soon as distilled water has been exposed to the air, its starts absorbing Co2. Eventually once enough is absorbed, the ending "distilled" water has an acidic PH or at least more acidic than tap water.

 

Yet I've never seen a professional shop use tap water in my entire life. Go figure.

 

No, that's deionized water you're thinking about. Deionized water will react with some metals, causing lots of corrosion. Tap water is certainly not best. When you heat tap water, certain minerals will settle out. Plumbers refer to these minerals as "temorary hardness". Open the drain in the bottom of your hot water heater and see what comes out. That's what's settling out in your car's cooling system when you put tap water in it.

 

Water has been called the universal solvent. The purer the water, the more of whatever will dissolve into it until the saturation point is reached for that substance. Aluminum is no exception. Ideally, you'd like to add water that was already saturated with aluminum. Tap water from most municipal sources has some amount of chlorine, which will act as a catalyst, and speed up the dissolution of aluminum. Plus as pointed out above, tap water usually has some other minerals which can precipitate and deposit sediment in your cooling system. But, even though distilled water is more corrosive to aluminum than less pure water, the fact that its supposed to be mixed 50/50 with DexCool needs to be factored in. DexCool contains corrosion inhibitors and acid neutralizers that counteract the tendency of water to dissolve the metal parts of your cooling system. I'd rather leave the chlorine and sediment out of the equation and go with 50/50 DexCool and distilled water.

 

Not to mention good ol' flouride. I don't think our radiators are worried about their teeth.

 

My bad. Meant to just say with stock thermostat car runs at 196 doing highway speeds. I do not know what stock unit is rated at although car seems to reach slightly over 198 before dropping back to 196 indicating the thermostat opened and full coolant system is operational.

FYI - service manual says thermostat starts to open at 187 and is fully open at 206.

 

I only use Perrier.

 

One issue overlooked in this discussion is electrolysis in automotive cooling systems. The aluminum block and radiator will give up metal in a galvanic circuit is established with a more noble metal so having a pH balanced system is pretty critical and that is done with distilled water and GM's pH balanced anti-freeze. It may even be worth it to check the pH level periodically to make sure it remains neutral.
On the subject of hot water heaters, one individual mentioned the junk that comes out of the hot water tank when it is flushed is from solids in the water accumulating in the tank. That isn't really true. Hot water tanks have a sacrificial anode installed in them and what you see when you flush your tank is anodic material that has sloughed off the sacrificial rod. Softened water systems will exacerbate the issue due to the sodium ion exchange, in other words, softened water is actually salt water. It isn't a lot, but it is there. It is a good idea to periodically inspect and replace the sacrificial anode at specific intervals to maintain protection against electrolysis.

 

You can pick up about five degrees cooler overall by taking your fuel rail covers off...They are like a blanket on the top of the engine...Engine can radiate heat more easily...

 

No, it's due to temporary hardness. The heat causes calcium bicarbonate to break down into calcium carbonate, which is much less soluble. Google it.

 

Here's my two cents worth. Almost 45 years in the automotive background. My 2008 Z51 A6 runs @196 F. If I stop in traffic with A/C on and out side Temp is 100 F while waiting at a traffic light for a minute or two the temp will climb and get up to 220 F then the cooling fans will kick in at a faster speed. It will then cool down. As soon as I take off it goes right back to 196 F. So 200-220 might be a little hot it's not by any means overheating. (Stock Thermostat) Now Your radiator holds a larger amount of coolant then the engine. As your engine heats up the thermostat begins to open to allow the lower temp coolant in radiator to flow into the engine (Which is hotter then the coolant in the radiator) So the engine begins to cool down. The thermostat regulates the flow to keep the coolant in the radiator lower than the engine. The air flow thru the radiator cools it down. IE even if the the outside air is 115 F it's still cooler than 200-220 in the engine. So that's how a basic cooling system works. Hope this will help. As for some of the other info most of it is correct. Enjoy your car its designed to run 200-220. A lower thermostat like a 170 or 180 or even a 160 only begins to allow the flow from radiator sooner @ a lower temp but once that Thermostat is open it will NOT change the operating temp.

 

Want 200-220*F for reduced engine wear, and to maintain efficiency and economy.
All power plants no matter what type are more efficient when temperature is higher.
Engines which make frequent short trips are known to have excess wear, so this is both a wear/tear issue and efficiency issue.

Next, NEVER use tap water in anything you care about. Worst possible content liquid which contains innumerable substances and varies greatly.

Always use distilled water as it will not conduct electricity easily and is free from contaminants.
By mixing distilled water with at least 10 to 20% engine anti-freeze (Your choice) you will add the necessary pH and ionic stability.
Although it is nary a concern in a previously run cooling system, as the previous solution (from the factory) even after excess flushing with distilled water, will still contain myriad ionic and anti-freeze related molecules. In other words, you cannot truly flush a cooling system free from ions, so regardless of whether you add anti-freeze or run 100% distilled water it will still become 'dirty' due to previous inhabitants.

And more to the point, it is a standard rule for 'real' race tracks that one must use only 100% water, to avoid having antifreeze on the track.

 

When I was a wee lad (seems to be 150 years ago) my mother told me never Trust a Gypsy... they'll kidnapp me and and make me a slave!... Been weary of the gypsy ever since!... However, this one is correct.!

 

He's not when Dexcool is brought into the equation. He's completely wrong.

 

He's thinking of deionized water, not distilled. Deionized water will attack certain metals, including iron and copper. Not as bad for aluminum, but still...

 

I've worked with Deionized and ultra-pure water for many years in research applications. When performing PCR or growing cancer cells for example the liquid media needs to be absolutely pure pure pure from all contaminants.

There is some truth to ultra pure water pulling ions from nearby materials, but this only happens if the device you are pouring the water into is absolutely pure and clean, such as a sterilized stainless steel tray for an incubator which is never exposed to air or a pump or dissimilar metals. In which case a pinch of sodium bicarb is added to provide some ions in solution.

A automotive coolant system is not pure, or clean, not even when brand new. Even just the slight dust and burrs created from manufacturing or by friction of moving water through a tube is enough to dislodge ionic components and satisfy the water. It doesn't take much. In other words if you pour pure water into a automotive cooling system, then quickly drain some out and test it even after just a few seconds, it is already so filthy and so contaminated with all manner of debris including DNA, pollen, bacteria, fibers and skin from animals and trees, all manner of dust, and of course any engine byproducts of minuscule amounts as oil, rubber, paper, whatever gaskets are made of, and of course anything that was in there before you filled it from being previously run including but not limited to previous anti freeze and coolant-like molecules (reacted under heat and pressure in a previously run system creates myriad compounds) that it is absolutely preposterous to think that any kind of water no matter how pure is going to scavenge ions due to being so pure once it touches that automotive system.

completely crazy talk

 

Yes, normal temps, since the engine wants to get the motor oil hot enough to boil any water out of it.

Lower temp T state will decrease the normal temps that the motor will be at during light gas pedal use crusing about 20 degreese, but as soon as you get on the pedal harder, temps will climb back up to normal.

As for changing the temp that the raditor fan comes on to a lower ones, double edge sword since the OEM fan was not designed to be run that much. So what happens with the fan temp set too low, fan runs too much, and will do a melt down on the radiator fan on the right hand side of the radiator. Guys will remove the connect, do a hard wire of the wires at that location, causing the next melt down to be at the PWM (radiator fan controller instead)..

So yes, by holding the engine temp lower with better radiator/fans/controller, you can gain some more HP with the motor running cooler, but since the motor oil temp may not get hot enough to boil any water out of it that it collects when you shut the car down and oil cools off, can cause water corrosion problems in the motor isntead.

Simply, how far down the rabbit hole would you like to go, to only gain a few HP in the end.
Hence lower T stat and radiator fan table tweaks are just a short cut band-aid, and will pay for these cheap short cuts in the end with outer problems isntead.