should I add normal water to my cars radiator? Answered


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i have a 95 subaru impreza , im getting mixed responses to my questions. any mechanics in the house?


Depends on how much you need to add.

If it's just a cup or two to top it up the that's ok.

But if you need to add more then you need to add water/antifreeze mix. Go to a garage or oil change shop and let them add it. They have premixed water/anti and you don't have to waste the antifreeze.

If you need to drain and then refill you should refill with 50/50 mix of water and antifreeze.


They also have green tinted water they sell as antifreeze. I've seen it happen firsthand.

Simple maintenance should be done at home. It's the best way to know care has been taken to do it right. Also because antifreeze is cheap enough and the corrosion inhibitors in it get spent, it's good practice to fill the circuit with antifreeze only.

(1) Anti-freeze alone freezes at 0F to -5F, only with the addition of water is the freezing point lowered.

(2) Heat transfer capacity is greatly diminished by neglecting to add the water, on the order of 35%.

(3) Water is important for the suspension/emulsion that keeps the anti-corrosion additives active in circulation, as opposed to settling out as they are want to do in the jug.

There's been a law in progress to require that manufacturers add a "denaturing" chemical to antifreeze -- something smelling awful -- to discourage dogs from tasting it.

(Cats actually can't taste sweetness, if I remember correctly. That doesn't prevent them from being poisoned by the stuff.)

There are two main reasons why a automotive cooling circuit should never be filled with tap water: scaling and corrosion.

Scaling is a fairly obvious thing: water has dissolved minerals that become solid as the water evaporates. Eventually the whole circuit get coated with scaling that both slows heat transfer and blocks the thin tubes in the radiator.

The most prevalent form of corrosion is called galvanic corrosion. Basically, the whole circuit usually has different metals (imagine an engine with an iron block, and a aluminium head or radiator). When these metals are in electrical contact with each others, there is a electrochemical reaction that speeds up the corrosion of one metal and slows the corrosion on the other. While a part may not fail due to corrosion in a near term, the corrosion process releases rust or aluminium oxide into the coolant, once again blocking passages.

The main thing antifreeze does is to stop corrosion. It also won't scale the circuit because it doesn't have dissolved minerals. Because the corrosion inhibitors in the antifreeze are depleted as they're used to stop corrosion, it doesn't hurt filling the whole circuit with antifreeze. Change it once it looks rusty or has little metal particles in it.

Antifreeze(coolant) is mixed with water 60/40 ratio is to prevent the water from boiling over during summer operation and from freezing in winter.If you were to use 100% coolant , your engine would never reach it's designed ideal operating temperature .

Not true.

The flow of coolant to the radiator is blocked by the thermostat until the engine reaches the operating temperature. The radiator only dissipates excess heat (the energy that causes the engine to run over the ideal operating temperature range).

"Coolant" doesn't have to be antifreeze. Antifreeze doesn't carry heat significantly better than plain water. It simply has a higher boiling point and much lower freezing point.

antifreeze is 60% Ethylene Glycol
it is a Coolant and heat transfer agent

A mixture of 60% ethylene glycol and 40% water does not freeze until temperatures below -45 °C

.  No.
.  As has been pointed out, one of the major reasons for using antifreeze is for the corrosion and galvanic protection. Back in The Good Ole Days, car engines were made mostly of the same metal - iron/steel - and you could get away with running a weak AF solution. Nowadays, engines have aluminum, steel, and other metals which can react with each other. If you dilute your anti-freeze, the corrosion protection is weakened. Use a mix of AF/water (follow manufacturer's recommendations) whenever you add coolant.
.  If you must use water to top off your cooling system, use distilled water and use as little as possible.

While pure water will work in a pinch IF temperatures never drop below freezing, (a) it can destroy the engine if it does freeze and (b) it doesn't contain the anti-corrosion additives which are common in modern antifreeze mixtures, so it probably isn't as good for your engine as the proper dilution of antifreeze.

The owner's manual will tell you what the manufacturer recommends. Generally it's worth following their advice... and they will almost certainly tell you to use an antifreeze mix.

I just stick with a mix suitable for year-round use in my climate. The stuff is cheap, after all.

Besides the use of anti-freeze/anti-boil additives depending on your climate, you should also think about your local water supply. If you have hard water, you're going to get mineral deposits building up inside the radiator, which can both affect the flow rate, and potentially corrode the channels. If you have distilled water, use it. If it's an emergency, as Bass said, use what you've got!

If you live in a climate that ever experiences temperatures below 32F, you will definitely want to use antifreeze. There should be no big issue using normal water temporarily if it is an emergency and you are stranded in the middle of nowhere, but otherwise I would use antifreeze.