Cooling System Issue, Sticky hoses Options

[kavy]

Guys, i've noticed something rather peculiar with the cooling system of my car from about a week.The coolant level drops by about 100ml from time to time and with this, the radiator hoses become sucked with pressure developed within the cooling system and released on opening of the radiator cap.There are no visible leaks whatsoever and the pressure is normal upon testing by a friend.Also refilled coolant after getting the whole system flushed making sure to burp it for removal of any air bubbles. Could it be an issue with the thermostat ???Are the hoses reusable ???And is it that my radiators time has expired ???lol. I'm lost.

[kavy]

Argh,i knew i missed something out in the write-up but the radiator cap was the first thing i replaced..Ok, another thing i forgot to mention was that sometimes when the vehicles temperature reaches its normal operation,i open the bonnet and see that the hoses have collapsed but since it is best not to open the cap and refill it,i drive it back home and see that the hoses are fine.I stress the word "sometimes" because the usual scenario is that i end up having to open the cap on seeing that the hoses have contracted,which releases air pressure it has built, further decreasing the coolant level to the mentioned 100ml or so which i eventually have to fill up.I really need some pointers on what the problem may be so that i don't have to end up changing something that was not the cause..I'll try changing the radiator cap again and see if the problem still exists but it really doesn't make sense that it would result in coolant level drop.Right?