1987 Golf Heater Problem

The heater on my golf is only blowing luke warm air (even when turned up to red).
I have been told that the heater matrix might be blocked and needs flushing, how do I do this.
The system has been presure tested and there are no leaks.

Any suugestions for solving this minor problem?

I've never seen a blocked core, usually the core will just leak coolant into the floorboard when they go bad. More than likely it's the flaps in the air distribution box. They are metal with large perforated holes that were covered with a foam material that falls apart by now. You probably have seen some of it blowing out of the vents. When this happens you only get weak heat (even in the cool position). I always replace the material when I do a heater core on them, I use foil furnace tape to close off the holes in the doors. You can also check that the temp control lever is still hooked to the flap control arm at the bottom of the air box, if you hear the flap moving then it is probably okay.

Thanks for your reply.
Since my post ihave detected a small leak in the radiator and a small split in the hose to the heater matrix. Could these be causing the problem?

Thanks.

Colin.

The loss of coolant may cause the engine to eventually overheat. The (hot) coolant flows through the heater core all the time whether you request heat or not. The air distribution box's flap position determines if the air blows across the core & into the car. If the flap closes properly & you still get heat the foam that seals the holes in the door is probably gone & letting air across the core, a very common problem. Have you seen pieces of foam blowing out the vents.