a few months ago i had to change my thermostat due to it breaking (it looked like something had forced its way through it breaking the spring bit off) and then the next day the expansion cap broke (the top cracked off)

now i have noticed that the water level drops from the max mark to inbetween the min and max in less than 100 miles of driving (i check it every week and top it up but it never goes less than this)

i don't use the a/c much and the car has never overheated or in fact had any other problems, it has been very reliable

another point which might relate to whats happening is that it is also using more oil than normal about a quarter of a litre every 4000 miles

there is no smoke in fact the mot emission test that i had done recently was lower than last year!!! there is no mayo in the oil and no visible leaks or any other signs of anything else wrong but the water and the oil must be going somewhere!!!

am i worried about nothing or is this the beginning of large repair bills??? (i really don't want to get rid of it as its been the best car i've ever had)

any suggestions...