MBMB

Why would I need antifreeze in Houston in the summer?

Can I run straight distilled water if I change it before there's the remotest chance I'll be driving somewhere cold?

Thanks,
Mark.

UKKid35

I thought antifreeze was mainly used as a corrosion inhibitor, you don't really want to risk having to change those head gaskets do you?

Vlocity

Mark:

As Paul indicates you will wreak all kinds of damage in your engine by not running a good antifreeze. In addition to inhibiting corrosion, the coolant additive also lubricates the water pump and most importantly will increase waters boiling point.

Run a good coolant and change it every other year.

Regards,

Ken

donberry

I found some Zerex at autozone that is phosphate free and it was only 9.99 a gallon.

Old & New

Not really. The addition of ethylene glycol raises the boiling point a few degrees, but it is primarily the pressure maintained in the cooling system which elevates the boiling point. In fact, I would venture to say that this may be the sole reason why cooling systems are pressurized...

MBMB

Thanks, all.

Vlocity

Hey Old & New:

Enlighten me. I'm disagreeing with your comment. But I don't understand?

Why is it that most coolants list a boiling point that is higher as the concentration of antifreeze increases up to say 70%. I've seen some listed as high as 276 degrees with a 70/30 ratio.

I thought possibly it had something to do with the mixtures carrying capacity?

And what exactly does water wetter do?

Regards,

Ken Bigham

Jim bailey - 928 International

a 50/50 mix raises boiling point to about 130 C . Water wetter I believe breaks surface tension of the water it does however LOWER the boiling point (My guess is it contains alcohol) .

ViribusUnits

Ethylene glycol without a question both increases the boiling point, and decreases the freezeing point of water. Well, of the mixture. This is because ethylene glycol has a very high boiling point and "get in the way" of the water molecules trying to excape from the surface of the liquid. This is not a precise way to think of it, but it is adquite. I could go into Roualt's law, but that would be somewhat pointless. At atmospheric pressure, the boiling poing of a 70/30 ethylene glycol/water mix is around 113 C.

Automotive coolent systems are pressurized also to prevent boil overs. Increaseing the pressure in the coolent system by 7 psig puts the boiling point of pure water at around 112 C. This is based on a corrlation by the Antoine's Equation.

Figureing the boiling point pressure of a pure substance is pretty easy. It's the multi componet systems that it's not so much fun. Anyways, back to the subject at hand. Clearly each methoid will increase the boiling point, and boil over protection. If you use both, that is of course better.

Antifreeze also contains rust and corrosion inhibiters. There purpose is pretty ovious.

However, i don't belive it luberates the bearing for the water pump. The bearing, IIRC, is of a sealed design, and shouldn't be imersed in the coolent.

Randy V

Most race cars are required to run straight water for cooling - the main reason being that a loss of coolant will not contaminate the track with slippery glycol.

donberry

you are right about the pressure raising the boiling point. Makes a huges difference. While antifreeze will raise the boiling point, it is still being under pressure that is the biggest part I believe

SteveG

On my "other" car, I changed the coolant that had been in there for probably 5 years if not longer, I just know it had maybe 50,000 miles that I put on it. I don't know what the mix was, but I put in 50/50 and it has run a lot cooler. It didn't run hot before, but the change was dramatic. My theory is the coolant is more efficient at removing BTUs, but then it must not be critical or the racers would have a problem with the pure H2O. Thoughts?

ViribusUnits

To determin which provides the most protection from overboiling, you need to first know the mixture of the antifreeze, and the pressure rating of the cap.

As the numbers I posed above, a 7 psig pressure cap is about as effective as a 70/30 antifreeze/water mix at preventing over boiling. Each raise the boiling point of water by about 12-13 degrees C. Now, the results are not exactly additive, but you get the picture, right? (I'm not sure if a 70/30 antifreeze/water mix at 7psig will boil higher or lower than the additive of the two at 124 C.)

Pure water will remove heat more effectivly than any antifreeze/water mix or pure antifreeze. Because of this, I usualy try to run around a 50/50 mix. I figure it's better to get rid of the heat, and not approch boiling over, than it is to get into those higher temps. As of yet, no problems, and I've got one summer under the belt in the 928. I'm starting to look into a second.

Vlocity

Thanks for the replys. Solid information.

Regards,

Ken Bigham

Old & New

Here is the boiling points of water at various pressures. The addition of a solute (ethylene glycol in this case) makes up the difference to the number on the label that the antifreeze manufacturers would like you to attribute to their product. Note that it boils at room temperature in a vacuum!

Water Wetter is supposed to suppress formation of steam bubbles at the hot spots in the engine.