Heater problem

[Mog1960]

Hello
my heater only blows barely warm air. Then goes cool after 15mins or so then I get the ’warm’ air again. any ideas anyone ?
thanks

 

[André4Renaults]

It sounds like it might be an airlock. If an airlock is in the system it will gravitate to the highest point, which is the heater matrix. Assuming the rest of the car's cooling system is functioning properly, I'd suggest bleeding the system, using this method:
1/ Raise the expansion tank so it's ABOVE the height of the rest of the heating system. A good way is by supporting the expansion tank on the open bonnet using a bent metal coat-hanger.
2/ Start the engine and ensure the expansion tank is full of coolant.
3/ Put the heater controls to maximum hot and switch the fan on. Open the bleed nipples adjacent to the heater matrix, allowing the air to escape and only tighten the nipples when coolant runs freely from them.
4/ Ensure the coolant level hasn't dropped below the lower point of the expansion tank during this operation.
5/ Feel for increased hot air coming from the heater outlets! It should be much hotter, if a load of air has been removed from the system.

 

[Mog1960]

Thank you. I’ll give it a go and let you know.

 

[mr-reno-139]

thermostat missing or faulty jammed open is possibility

 

[Mog1960]

I gave the bleeding suggestions a go yesterday and had coolant coming out immediately. Was going to give it another go tomorrow. I’m learning my way round fixing cars .... well, my R4. What thermostat do you mean and where is it?
thanks

 

[mr-reno-139]

a workshop manual would help
it lives in radiator top hose
maybe search forum for info by typing thermostat into search box