l got a Peugeot 306 but my heaters only blow cold air. l checked my water and its ok and my Temperature stays on 80,if im stuck in traffic and put the heaters on it blows warm for 5secs then goes back to cold Straight after. l undone the bleed valve by the bulk head and no watercomes out of their unless you squeeze the top hose off the radiator. l also checked the thermostat and that opens when the water starts to boil. please help im frrrrrrreeeezzzzzin

why does it sounds like faulty water pump for me?

Your thermostat might begin to open at 100 in a pot of boiling water, but it should begin to open at 88 -90, & be fully opened at 100 degrees Centigrade.

You must check for a non-opening thermostat, & a non-efficient water pump.
1. Start the car cold, & open the radiator cap. Cooling fan should not be on. Constant fan will not allow ur water to heat up.
2. After 5 minutes, u should hear the engine idling sound change, the thermostat should begin to open, & u will see water circulating past the fill neck. This means the thermostat is open.
3. After 3 more minutes, put ur hand carefully!! on the radiator fins, not the plastic top. Are they hot? NO? Then ur water pump is inefficient.

Get back to us with the results please.

PS: after testing the thermostat, did u replace the old one? With spring INSIDE the engine? or take that moment to install a new one? Yours is probably 10 years old anyway?