Well, where to start... I have an issue with the coolant and need some advice/experience of the bunch of people here.
The issue: when driving for longer distances the overflow bottle get's filled, I loose about 200ml of coolant and there are bubbles coming up in the oveflow bottle. This only happens, when engine was completely cooled down before driving.
When I have reached my destination, I usually refill the radiator after letting the car sit for an hour. The radiator is full then and the coolant bottle is on min marking.
When the car cools down completely (e.g. sitting over the night) the overflow bottle empties itself towards the radiator.
I have found that this happens more, if I use to drive with under boost a lot. The effect is nearly not there, when I drive with 130km/h constantly on the motorway. In any way, oil temps are moving between 90 - 105 °C, but not above.
The car:
- alloy radiator from the group buy with 1.3 bar rad cap (was there with the std. radiator as well)
- HKT low temp thermostat 71°C
- new coolant (green, no OAT stuff)
- no visible leaks
- ECU temp sender changed
- radiator fan changed
- changed the radiator cap - no improvement
- full cambelt service with brand new water pump 3 years/5000kms ago
All parts have been on the car for max 5000kms and I had this issue for a longer time now. We logged the temperatures with EvoScan and the car reaches 100°C on idle easily, fans kick in as expected. I did not had the time yet to check temperatures while driving but even with 20°C ambient temperature this happens.
We did perform a check, whether there are residues of exhaust gases / water and did not detect any residues of water in the exhaust gases yet, nor did we found exhaust gases in the cooling system. There is no white smoke, nor do I have any residues of water in the oil.
Next is to perform a coolant system test if there are any (visible) signs of leaks.
On a sidenote: I found some oil build up, running down the intercooler pipe (after Y-pipe) after 400kms driving - although I cleaned it before.
Has anybody heard of hairline cracks on a 6A13TT?
Can a faulty turbo cause this to happen? (e.g. pressurize the cooling channels)
Any other ideas, as the head gaskets seem to be fine?