I have a Ford Transit Bj. 1996 2.5 Diesel vacuum cleaner. I have already done a lot: – Injector nozzles cleaned (injector cleaner + ultrasonic) – Intake manifold cleaned (was real like soot in about 1cm) – in front of Kat clamped down and tried out I had also once unscrewed the thermostat, because cooling water was out. The seal was gone… I then thought that it works better with Loctide surface seal … well wrong thought -> on test drive the cooling water is complete The engine was at a good operating temperature for the first time and went really well for the first time, of course only until I realized that the cooling water was empty, then I was right on it and filled it up. Well long speech short sense… My guess is that the thermostat may be broken (time open) and therefore the engine will not get really warm. The cooling water indicator is always so at the bottom of the “normal” marking. Makes sense and brings it What if I exchange the thermostat? Would be really happy about a tip!