possible stuck thermostat

hi everyone
i have a 2001 passat pd 130 that i have to weekly top up with water i do 500 miles a week,and the car is losing water but with no visible signs of a leak,just a few drips on the drive. i have had a system pressure test and the CO checked in the expansion bottle both fine,i taped some tissue around the cap and overflow under the bottle just to see if either get wet,and suprise suprise its the overflow thats leaking out the bottom of the bottle the system is pressurising so much its shooting the water out the overflow,when up to normal operating temp (with engine off)the expansion bottle water is below its lowest level indicator when the cap is released the pressure near enough refills the bottle with water,does this sound like the thermostat is stuck shut or am i being optimistic and its the dreaded HGF l:1zhelp:

If the thermostat was stuck shut the car would almost certainly overheat all the fans would come on and ur temp would go up and the warning light would come on is ur temp rising?.Any modern car that runs low on coolant does exactly what ur car is doing its the water boiling and expanding in the system it has to have somewhere to go in ur case as with most others the overflow and filler cap,these models have a tendency to leak from the water pump check this out and look for staining around all ur water hoses take ur thermostat out put it in a pyrex dish fill the dish with boiling water and watch to see if the thermostat opens fully if it does its ok.I am assuming u have no water in oil or oil in water . Ed

thanks eddie
no probs with it overheating and i took of the top cam belt cover and all that was dry i am stumped,and i thought the french made **** cars lol

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Originally Posted by mark740_5

thanks eddie
no probs with it overheating and i took of the top cam belt cover and all that was dry i am stumped,and i thought the french made **** cars lol

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hello mate i had the same problem it turned out to be the oil cooler