Passat 1.9TDI Heating & Cooling Riddle

[turbo turnip]

Hi I'm a Newbie

My 2001 Passat developed cooling 'problem' on motorway. Alarm sounded and message to check coolant level - temp hit 120. Coolant level OK. When temp gauge goes up it does it very quickly. Thermostat has now been changed, as it was thought this might be the cause, but problem still exists intermittently - almost guaranteed as soon as I get on the motorway but has happened once in town as well.

Additionally, and this started later than the above but coincidentally after the thermostat had been changed, Climatronic randomly allows heat through both on Auto and Manual settings - sometimes no heat, sometimes a little and sometimes scorching irrespective of temp setting - sometimes even works normally!!

Are these separate problems or could they be linked.

Any help appreciated.

[northern bloke]

Hi,

My Passat 1.8T developed the same kind of problem, the thermostat light came on followed by a STOP on the dash. I checked the coolant and indeed it was low, filled it up and on I went. The climatronic aircon started misting up the interior, all windows with a syrup type film, engine coolant. the other sign was damp on the passenger floor, lift up the mat and check, it'll have seaped through the carpet if a leak in the car is present also a fishy smell will be about. The aircon and engine use the same coolant, the garage said it was the Evaporator at £400 big quid + £300 to fit and an independant aircon specialist said it was the Heat exchange/Heat Matrix at £100 + £250 to fit. It was the Heat Matrix.
Coolant/Anti freeze was leaking and evaporating into the car. Needless to say dangerous and poisonous. hope this helps