overheating while idle

[MikeW]

Originally posted by mdbrandy

I'll try to turn the fan when I get home from work tonight. If anyone knows what SportZ issue the fan clutch article is in, I'd appreciate it.

While it doesn't specifically talk about repairing the fan clutch, the Summer 2003 issue has an entire article on solving overheating problems in early Z cars. It starts out telling you how to properly measure the temperature and covers the thermostat, fan clutch, radiator, etc.

[Daniel]

Since all the worst has been covered,How 'bout some basics. Make sure the fan belt is tight and not worn. Remember when forcing air thru the radiator( MOVING),the fan and water pump are not at maximum demand. Next is the status of your antifreeze.A 50/50 mix is optimum. Pure antifreeze will freeze before a 50% water mix. The over heat will occur when the "antifreeze" breaks down.It is coolant. Each time your car hits normal temp the "antifreeze" form a protective sleeve in your engine to keep the hot from the metal. When the car cools the "platelets" release growing less sticky each time. Soon they don't bond at temp anymore. Theory has it if you never let your car cool down,Your coolant would never wear out as its the hot/cool change that kills it.

[Bambikiller240]

Originally posted by Daniel

.......... Each time your car hits normal temp the "antifreeze" form a protective sleeve in your engine to keep the hot from the metal............

If the "hot" never comes in contact with the metal due to anti-freeze properties, how does a radiator cool the "hot" water. The heat must be transfered to the metal so that air flow can transfer the "hot" out of the closed system into the air as it flows through the radiator.

[mdbrandy]

According to the tech article that bambi posted, pure water is actually a better heat transfer agent than a antifreeze water mixture. I don't know if this is because the antifreeze lowers the heat capacity of the mixture as compared to water, or because the heat transfer coefficient is decreased by the antifreeze in the water. Pure water has a very high specific heat, and designed correctly, a heat exchanger (radiator) using water alone would be very efficient. However, then your cooling system would corrode away, and your block would crack when the pure water froze. I'm somewhat skeptical that pure antifreeze would freeze at a higher temp than an antifreeze/water mix, but I'll reserve judgment until I look it up.

[Daniel]

Carl, Its not an absolute shield, no more than your sweater is an absolute shield from the cold. As for you non-believers about the pure antifreeze freezing before a 50/50 mix I will repost this becoming annual post in the morning(notice Carl didn't question that ?---this year !) This is a paste from PEAK website.

A. Why is it important to mix antifreeze with water?

Antifreeze contains chemicals that protect your engine against rust and corrosion, as well as freeze-up and boil over protection. Water is required to activate the chemicals in the inhibitor package. Furthermore, adding water to antifreeze actually increases the freeze-up and boil over protection provided. For example, a mix of 40% antifreeze and 60% water provides freeze-up protection down to -10°F and boil over protection up to 259°F. In comparison, a mix of 70% antifreeze and 30% water provides freeze-up protection down to -62°F and boil over protection up to 270°F. However, we do not recommend adding more than 70% antifreeze. This would limit the corrosion and freeze up protection and heat transfer capabilities of the antifreeze.

.

[mdbrandy]

Originally posted by Daniel

If you are into science the water is the catalyst of the chemical process.

Sounds like a challenge to me. FYI, heat transfer is not a chemical process. Mass transfer, maybe.

A little data on glycol/water mixtures:

At 180 degrees F

%glycol specificheat thermal conductivity

20% .974 .318

30% .914 .288

40% .880 .261

50% .866 .241

60% .801 .220

All in English BTU/lb etc units. The actual values aren't that important - it's the trends I'm after.

Obviously, a glycol mix has a lot lower specific heat than pure water, and can thus hold less heat per unit volume. It also has a much lower thermal conductivity, which will lower the heat transfer coefficient at the boundry layer (i.e., the metal/liquid interface).

I haven't found freezing points for pure ethylene glycol yet.

[Bambikiller240]

Originally posted by Daniel

Carl, Its not an absolute shield, no more than your sweater is an absolute shield from the cold. As for you non-believers about the pure antifreeze freezing before a 50/50 mix I will repost this becoming annual post in the morning(notice Carl didn't question that ?---this year!) If you are into science the water is the catalyst of the chemical process.

My point is that antifreeze is not any kind of shield (to heat), it does not keep "hot" from metal. See EDIT at bottom The coolant, whether water or a mixture, is there to transfer the heat out of the system. Antifreeze's purpose is to keep the fluid mixture (water AND antifreeze mixture) from freezing in the radiator tubes, it's anticorrosive elements are there to protect the metal of the system from being disolved by the water in the mixture over time. I have no doubt that 50/50 mix is better than straight antifreeze, for the overall needs of the engine. i.e. protection from freezing and corrosion protection, but it is not more efficient at transfering heat.

Quoting from Red Line Products website:

Water has twice the heat transfer capability when compared to 50% glycol antifreeze/coolant in water. Most passenger automobiles have a cooling system designed to reject sufficient heat under normal operating conditions using a 50/50 glycol solution in water. However, in racing applications, the use of water and WaterWetter® will enable the use of smaller radiator systems, which means less frontal drag, and it will also reduce cylinder head temperatures, even when compared to water alone, which means more spark advance may be used to improve engine torque.

If anyone is interested, there is much more data to be found by following the link below.

Tech Information from Red Line Corp.

**EDIT Actually in that antifreeze/water mix is less efficient at removing heat, it is a shield; but that IMHO is NOT a benefit, it is a drawback that must be lived with in order to receive the benefits of ethylene glycol. Anticorrosives can be purchased separately.

[Daniel]

Mark, This is not a challenge, as I say its a yearly topic. Please note my edit of the previous post. I'm glad you find this interesting!

[Brett240]

yeah if you live in mild climate your best to use as little anitfreeze as possible. distilled water works best as the heat transfer properties of water are more effective than aftermarket coolants, tranfering the heat from the engine and out through the radiator better.

unless you live where you see freezing temps the only use coolant additives have is their rust protection ptoperties, so its a good idea to put some in. ( i use about a 20% ethlyglycol/water mix)

as for the benifits of coolants raising the boiling point of your fluid, if your engine gets hot enough to boil water in a pressurised coolant system then you have a more serious problem to worry about than your coolant mix.

[Bambikiller240]

Originally posted by Brett240

........... distilled water works best as the heat transfer properties of water are more effective than aftermarket coolants, tranfering the heat from the engine and out through the radiator better..............

Hi Brett240:

You may want to read the Tech Article that was posted to the site today. It offers a different view on the "benefits" of using distilled water in a cooling system that contains large amounts of aluminum.

You can find it

HERE

[Daniel]

My point is that antifreeze is not any kind of shield (to heat), it does not keep "hot" from metal---**EDIT Actually in that antifreeze/water mix is less efficient at removing heat, it is a shield;----- Why Gee Carl you've covered all the bases tonite huh???? (sorry i couldn't help it):stupid:

[Brett240]

Bambikiller,

i realise you didnt write this article so take no offense but this statement:

However, now the reasoning is to use regular tap water because water normally likes to have ions floating around. If it doesn't, then it gets them from wherever it can. Aluminum readily ionizes, so the distilled water "steals" the ions from the aluminum

is crap.

Distilled 'de-ionized' water will not "steal" Ions from the aluminium. it will take nothing at all from the aluminium.

normal tap water has various flourides, calcium, ions and other deposits that build up on aluminium in areas and cause corrosion.

using tap water is a big cause of electrolysis corrosion in coolant systems, which destroys aluminium. Most Aluminium radiator manufacturers can do an electrolysis test for you on your coolant system to see if you have this, and will also recommend distilled water.

please avoid using tap water.

again no offence meant.