[dhanushs]

Originally Posted by Thad E Ginathom

That's not what I'm saying. Coolant is not additive. Additive is not coolant. Coolant is water.

Correct that additives help to prevent rusting. That's steel parts: I don't know about aluminium,

AFAIK, Just like Thad has mentioned, coolant is just water. And this is because, no other liquid has better heat carrying and dissipating properties than water.

And the "coolant" we add is just an additive, and the fuction of that is to
1. Reduce the freezing point.
2. Corrosion Inhibitor,
3. And prevent scaling of lines.
4. And increase the boiling point, just to an extent that water does not boil inside the engine block causing steam pockets.

We use distilled water or pure H2O, because the impurities, if any will settle on the sides of the tubes causing scaling, like in boilers, which considerably reduces the heat exchanger(Radiator) efficiency. Impurities like salts and minerals are known to increase the corrosive properties of the coolant exponentially.

Experts, please correct/suggest.

[fordday]

This is my first post in t-bhp. I have a 2001 Ikon 1.6 zxi. For the last few months there were coolant leakages (few drops a day) from the thermostat housing. Went to fng, when he opened it, saw that the thermostat gasket is completely gone. He sealed it with Anabond but said it will need replacement soon.

Last week after a 5 km drive, saw coolant dripping all the way. Opened the hood, coolant and vapour coming out of the sides of the coolant tank cap. This meant it acts similar to safety valve in pressure cooker. Cap was still tight but too hot for touch. After 5 mins when I restarted the engine there was again vapour coming out from the sides of the cap. Went Lathangi ford, had to replace Thermostat, ECT, connection water out and refilled coolant. They said the coolant level went too low and it got overheated. In a typical ford a** way they billed me for about 7k.

[khoj]

Originally Posted by fordday

He sealed it with Anabond .

The cooling system's fate too was sealed right there.

BTW did ford replace the radiator cap or not. If not then do change it irrespective of people telling you otherwise.

[Thad E Ginathom]

Cap was still tight but too hot for touch. After 5 mins when I restarted the engine there was again vapour coming out from the sides of the cap.

This might be a good point to mention...

Never attempt to remove the radiator cap on an overheating engine.

Short of driving into a wall, it is one of the most dangerous things you could do with a car. The jet of steam and boiling water is quite impressive.

Yes... I learnt this the hard way (even though it is something my father would have taught me a a child) and it is a miracle that I was not injured.

[vivekiny2k]

Originally Posted by khoj

Now that we have turned this into Thermodynamics 101, could you elaborate how the pressurized?? cap keeps the coolant from boiling and why the drop in boiling point would not matter(not that Hashim meant it that way, the gist of his statement being quite clear).

All these years I understood that the cap is designed like a last resort safety valve which will let out a required amount of steam+concentrate+hot water mix after all other safety features built into the system fail to keep things in check and when the system pressure continues to rise beyond a certain set value and restore sanity. Seems it is time to learn something new.

all physics is nothing but laws of nature

a liquid starts boiling when it's internal vapor pressure equals atmospheric pressure. At this point the liquid kind of controls it's temperature by boiling off a lot of vapor. at mean sea level water does it at 100C. so you can never heat water beyond 100C at MSL, you can get superheated vapor though (.

at lower pressure, e.g. in Laddakh, the since the pressure is low, water starts boiling at lower temperature, since it's vapor pressure at say 95C equals the reduced pressure there. In other words you can not heat water to more than 95C in that area, and that makes cooking so difficult.

at high pressure (e.g. pressure cooker), you can actually increase the temperature to a much higher degree by not allowing water to boil, and hence to self control it's temperature. That makes cooking so easier.

Similarly, in vehicle's cooling syste, by pressurizing, you are letting the liquid heat to a much higher degree, thereby increasing it's capacity to take heat out of the system, and disperse it into radiator. If it's not pressurized:
1. the liquid will soon evoparate into atmosphere, needing frequent refills. remember old cars
2. will be less efficient since it is carrying less heat out.

Originally Posted by Hashim

Let me explain what I meant actually, we all know plain water boiling temp. is 100 deg. C so if we put plain water in radiator, it should start boiling as soon as it reaches 100 deg., now our "Coolant" is increasing boiling temp. of plain water to say 500 deg. C then it won't boil at 100 deg. so its doing good for us

so you did mean increase boiling temp. But as I mentioned above, we use pressurization as the effective technique to handle high temperature, and not depend on additives.

Originally Posted by fordday

This is my first post in t-bhp. I have a 2001 Ikon 1.6 zxi. For the last few months there were coolant leakages (few drops a day) from the thermostat housing. Went to fng, when he opened it, saw that the thermostat gasket is completely gone. He sealed it with Anabond but said it will need replacement soon.

Last week after a 5 km drive, saw coolant dripping all the way. Opened the hood, coolant and vapour coming out of the sides of the coolant tank cap. This meant it acts similar to safety valve in pressure cooker. Cap was still tight but too hot for touch. After 5 mins when I restarted the engine there was again vapour coming out from the sides of the cap. Went Lathangi ford, had to replace Thermostat, ECT, connection water out and refilled coolant. They said the coolant level went too low and it got overheated. In a typical ford a** way they billed me for about 7k.

if you saw radiator cap leaking out the coolant, that was wrong. It should leak into the reservoir, not outside completely. either your radiaor cap, or the opening where it's fits on the radiator is faulty.

[Hashim]

Welcome fordday to the forum, even my m1000 thermostat housing was leaking coolant drops by drops and one day I had enough time to open the housing(and appetite for DIY), get the new gasket and replace it myself. No leaks after that! It cost me just rs.10 for the packing and I had the threebond tube at home.

You should never let coolant level go down else it may even result in engine damage due to overheating. For this have a look under the hood once in a while and check coolant container and all pipes for any sign of coolant leak (green/red color patches whichever color of coolant you use).

[khoj]

Originally Posted by vivekiny2k

all physics is nothing but laws of nature

Thank you professor.
So just like Hashim's initial post the gist of your statement was correct but inadvertently the word selection was not.

[fordday]

@khoj - so, now I will go for reservoir cap replacement.

@vivekiny2k - it was not the radiator cap leaking, but the coolant reservoir cap. I don't think there is a radiator cap in Ikon, I may be wrong.

@Hashim - thanks.

[vivekiny2k]

Interesting, I have seen it in my VW and thought i was a VW phenomenon. The reservoir is a part of the pressurized system, so the pressure valve is essentially a dry valve at the end of the reservoir. less complications IMO.

Then you are right, the excess coolant will go outside. but in normal operations the excess coolant should not be enough to reach that point. The A.S.S. did the change without diagnosis IMO. If they told you coolant was low, why change everything else.

At the age your car is, water pump, thermostat, ECT, any of these could have been broken. I would doubt the pump though. in US the cost of labor for opening the system is so high compared to the cost of parts that when one opens it, they get all of that changed at once.