The car cooling systems components are radiator,water pump,thermostat,fan and hose.However when reserve tank always reduce in level everyday ,we might think that some of these components has got into problems but after replacing, the problem still occurs.Is it too obvious to say that the component material is also in problems too?
A slight headgasket leak could cause gradual coolant loss while being virtually undetectable. Large leaks would show through steam in the exhaust but a small leak would be undecernable from normal condensation. Larger leaks would also possibly result in additional pressure in the cooling system and/or loss of performance, but here too, a small gradual leak would not. Perhaps the only indicator you would find would be if you pulled and compared coloration of all the spark plugs. Steam in the cylinder would result in a cleaner looking plug.
Your right...two years is to young, even if you have put on a lot of miles. Even if you aren't the original owner and do not think you have any warranty, I would check with the dealer. If it turns out to be a known issue, even if it was never bad enough to warrant a recall, the manufacturer may help you out. It would be worth checking.
Have you tried contacting the dealer to see if this is a known issue for your year, make and model? You might also try googling the year, make model and the word "coolant". Just curious, what is the year, make and model, and how many miles so far? If that model has engine options, what engine and trans combination do you have?
Was a thorough check only done on exterior leaks? Coolant can also leak into the inside of the engine as well. Usually if it is doing that though you will have milky looking motor oil. Having said that, some vehicles (my van for example) seem to send some coolant through the overflow right after being topped off but after that will hold the same level. This is a bit below the add line so I could see where you might think it was constantly losing fluid but in reality it just holds at that level which is slightly low according to the mark. If on the other hand, over time it flat out loses all the coolant then there is a problem somewhere.
If coolant goes inside the engine,engine performance normally will be affected but it doesn't show that.I have been topping up the reserve tank everyday but the level continue goes down if i do not repeat the same everyday.