Mk2 GTI Heater Problems

Hi I have a 1990 Mk2 Golf GTi 8 Valve and the heater blows either luke warm or cold air despite being mid range on the temp gauge and heater on full red. Water levels are constant and no obvious leaks. Should I be looking at thermostat maybe or is there a common issue with these?

It's a common problem. There is foam material that deterioirates off the flaps in the air box that direct air flow over the heater core, thus when nit fall off you only get lukewarm air. You've probably noticed small pieces of the foam coming out of the dash vents at times, or stuck in the vent grating. Unfortunately the entire air box has to come out to fix the problem, just like when replacing the heater core. I use metal backed furnace duct tape to recover the flaps. You might consider a new heater core while you're in there as they don't last very long either.

cheers boschman will take a look.