try 2 type of test
1. engine dead cold
2. engine at normal temp
if no.2 fails, i.e. loss of pressure comapred to no.1 , you have 2 options -
a. hairline crack in cylinderhead or crankcase or waterjackets
b. worn/burnt headgasket maybe due to earlier high heat that was not address earlier
no.1 usualy are the joint/rubber pipes/coolant exp tank, etc,etc, anything that can break easily compared to metal.
heat expands metal, and possibly water loss only when you run the car.
have you covered all the basic steps?
some mechs sometimes dont have time to troubleshoot proper ,they follow their experience and gut instincts, but endusers end up paying for all their r&d.......
try this again
1. flush cooling system
2. flush radiator
3.fill with normal colored coolant-green would be the best
4.drive for 5 days as per normal , but check coolant regularly when engine cold- if topping up take not of how much is topped up.
5.drive for another 5 days, this time no revs above 3k, regardless of any vw tailing you
report back to this thread and others with similair problems/solution would be able to chip in.......
