I know, I know, this has been done to death and I have read a great many threads on the subject but I do have a couple of questions. Today I set about trying to make the car warm up a little better. The issue is that the car doesn't seem to warm up very quickly with the gauge barely getting out of the first white section unless driving in traffic or stationary. I thought this would be linked to the lack of warm air coming out of the vents. I started by taking the matrix bypass valves off and popped them in an ultrasonic cleaner. They were apparently free and I could blow through them easily. While all the pipes were off I stuck a hose through the matrix which seemed to be free flowing. I was also going to change the thermostat but I ordered the wrong one so stuck the original back in. Re-fitted the bypass valves and filled it with water and Wynns. I let the car idle for a good twenty minutes until it seemed the thermostat was open, hot water was running through the lower radiator hose and eventually the fan kicked in. However, there was no hot water getting past the alloy bypass valve and as a result no hot air out the vents. So, I took the alloy valve off and replaced with copper pipe as per the conventional wisdom. This time no hot water getting past the plastic valve. Next I replaced that one too with copper pipe. Now I have hot water flowing in and out of the matrix. The air coming out of the vents is definitely warmer but certainly not at a level I would expect. I have now drained the coolant (it was deffo dirty) and refilled with antifreeze and water. So my questions are, can the matrix still not function properly even though water is flowing through it or is my problem the diverter flaps? They have definitely lost their foam as a lot has come out through the vents. Also, am I asking for trouble with an unknown age of matrix and the risk of it bursting, having removed the bypass valves? Thank you in anticipation.