[duss46]

Seems the HVAC blend doors that control temperatures need to be reinitialized being the 3rd row has heat. Can do with ISTA.

It was the first thing I did after software update.

[Node]

Does that car have shutoff valve on rear cabin coolant piping??? Given both front and rear heating units are "in parallel" I wonder if it exists and gets stuck so does not close rear heat exchanger and suddenly most of the flow goes through rear one (for some reason)...

Given you already replaced half of a car I wonder have you tried to do at least BASIC diagnosis... Like blocking rear heat exchanger so no coolant can flow through it. Does front still exhibit same behaviour???

Because to me your issue sounds like front one looses coolant flow... Either all of it suddenly goes to the rear or there is some air lock or too low coolant level.

[Node]

P.S. You say you bled the system using vacuum. Have you performed all the necessary steps for that like overfilling coolant, pressing gas pedal for 10s, starting engine, getting messages on KOMBI, etc...???

[duss46]

P.S. You say you bled the system using vacuum. Have you performed all the necessary steps for that like overfilling coolant, pressing gas pedal for 10s, starting engine, getting messages on KOMBI, etc...???

This engine has a mechanical coolant pump, there is no service function to bleed the system. 

The heat exchanger is also replaced now, still no success.

[Node]

P.S. You say you bled the system using vacuum. Have you performed all the necessary steps for that like overfilling coolant, pressing gas pedal for 10s, starting engine, getting messages on KOMBI, etc...???

This engine has a mechanical coolant pump, there is no service function to bleed the system. 

The heat exchanger is also replaced now, still no success.

There IS a PROPER way to bleed the system. Which involves starting the engine just BECAUSE it has a mechanical pump... So you have not followed procedure described in ISTA even you told us that you did... Now half a car replaced because too difficult to read. And I guess customer pays for all of this, instead of just bleeding the system PROPERLY???

[duss46]

P.S. You say you bled the system using vacuum. Have you performed all the necessary steps for that like overfilling coolant, pressing gas pedal for 10s, starting engine, getting messages on KOMBI, etc...???

This engine has a mechanical coolant pump, there is no service function to bleed the system. 

The heat exchanger is also replaced now, still no success.

There IS a PROPER way to bleed the system. Which involves starting the engine just BECAUSE it has a mechanical pump... So you have not followed procedure described in ISTA even you told us that you did... Now half a car replaced because too difficult to read. And I guess customer pays for all of this, instead of just bleeding the system PROPERLY???

I wrote clearly in post #3 that the system was bled according to TIS / ISTA instructions. Previously I meant service function in ISTA to start the pump.