General Sei heater blows luke warm

[flapping lugs]

My sei's heater doesnt seem to get fantastically hot, unlike my cinq's used to. Ive only had the car a month, noticed there was no antifreeze in, so I drained the system and added some. Bled it all, but the heater is not brilliant (wasnt before). I notice that when you pull off the drain plug from the heater matrix on tickover, nothing comes out, but when its revving it comes out fine. The effect in the car, is that when you are sat in traffic it blows luke warm, but when you are motoring it seems ok if not brilliantly hot. Just wondered if this was normal.Theres no leaks or air locks in the system.???

 

[custard]

well it may be a worn water pump not shifting the coolant at low revs
possibly need to flush the matrix
since it can blow hot then your cock should be okay