disco cool heating

can any one help i have got a 1996 disco i changed the water pump 2 weeks ago and since then i can not get my heater to get hot, it gets warm but not as hot as it was before the pump change. i have tried to bleed the system by taking thermastat plug out and expantion tank cap off and topping water up but still running cool, temp gauge ok still getting to temp, not over heating.
and finally whats the best way to bleed the cooling system. thanks for the help.

Sounds to me like either your thermostat needs changing or you have a airlock in the heater matrix.

dissconnect the matrix hoses and fix the matrix up first then connect your hoses and you will know its then full, definatly an air lock in the system somewhere.

When I changed my radiator I removed the blank plugs both from the radiator and the thermostat, heater controls to hot and filled up the radiator with coolant mix through the plug on the radiator. I then replaced the plug making sure by squeesing the bottom hose no air locks.

I then continued to fill through thermostat and header tank, then started engine and ran with cap and thermostat plug out until thermostat opened, water from header tank runs into engine, and out thermostat, turned off and refitted blank plug.

restarted engine and observed heat at hoses still with header cap off, once all warm and heaters blowing hot button up and run to check for leaks under pressure, before driving on road. check again next day after run when cold because water can settle a bit.

Probably a scientific way of doing it but it worked for me.

Last thing is change the plastic blank plugs whilst you are at it, one blew out on me and nearly cost me an engine, rotten. and never saw it untill it broke off, total ****e so they are.

If thermostat and heaters were fine before, then air as mentioned.

thanks 2 u all