Sorry l that I write in English, it´s easier for me. I am German, speak Dutch as well, but writing is not that easy for me.
I have a 2003T which used to have real problems with cooling….(somebody dropped a gasket into the internal cooling system and the gasket was milled by the water pump into little pieces). I took the system several times apart, it took 2 seasons until I fixed it. Got now lots of experience…wit VP2003T cooling.
I would use a dive bottle with 200bars air. Connect a hose to the output next to exhaust and the other end to the dive bottle. Open the tap on the bottle and blow lots of air into the cooling system. I can insure you that all pieces will fly back into the water pump (200bars…). Forgot to mention that you have to remove the impeller.
Hope you know that the internal cooling system needs to be vented. The venting screw is on top of the engine next to the turbo.
On top of the engine, you will find a pipe going to the thermostat housing. Inside this 15mm pipe is a shim which reduces the diameter of the 15 mm pipe down to 3 mmm. If there is any dirt is in the internal cooling system, then this little hole will be blocked. Had the system blocked several times …..fixed it with the air out of the dive bottle …no joke…
Now the temperature on my engine is absolutely stable, 74 degrees plus mins 0.5 degrees., even after 10 hours of engine use. I have a digital sensor and temperature meter installed (Amazon € 10).
You need new gaskets in order to seal the cooling system. (There are two different kind of rubber rings be careful). If you use the wrong ones you can start to disassemble again. The rubber ring are ridiculers expensive from VP. You can buy them for a reasonable price from
www.parts4engines.com/volvo-pe...eal-fuel-washer-kit/
Wish you luck for the repair.
Frank