No hot warm coming into the cabin?

[neilbardsley]

We have a MK1 2002 Yaris.  The heat coming into the car has always been lukewarm at best.  I replaced the thermostat and it got a bit better.  Now winter is here it was just rubbish. The blower is working.  You could feel some different the blue cold v red hot dail setting.  I replaced the coolant and it actually got worst with no heat.  Today we checked the air filter and removed it.  Lots of air coming in but all cold.  

The heater matrix pipes are warm.  I'm guessing the hotter top one is the inlet because it's hotter than the lower pipe.  However, before these pipes get to the matrix there is a t junction to smaller pipes.  After this t junction the inlet isn't as hot??  The smaller pipes feed to below the left back of the engine.  Near the in manifold.  What are these pipes.  Any ideas on what might be wrong

[TonyHSD]

Hi, 

I have no idea how it is exactly on your car model but as described you may have air locked inside the cooling system. After any change of coolant, thermostat or water pump air bleeding is needed to make sure there are no air bubbles eventually left as these can cause even bigger trouble. If you start the engine, let it idle and set temperature to max hot and blower fan to speed 1, set to blow towards middle of dashboard and feet, you need to let it running for 15-20 min and watch temperature gauge, should stay at middle , open bonnet and check all hoses are hot on main radiator, touch the heater core hoses should be equally hot too and wait for the radiator fans to come on, then wait until they stop turning , you can set the blower fan speed to 2-3 or more and see how hot is blowing now, make sure you have some coolant ready to top up if necessary and before you start a doing all that make sure you have coolant in the expansion tank at max level. If this doesn’t help you may have a blockage somewhere along the hoses or heater core. 
Good luck 

[neilbardsley]

Thank you.  I tried to bleed air out by warming it up and opening the radiator cap a bit but that didn't work.  Is there a bleed srew on a hose somewhere?

[Madasafish]

Warm engine up, put  switch on  heater on to full heat  before you start and leave it there (Important)  and take off cap as you did.

Switch off engine - important safety.

Gently compress in turn all rubber coolant pipes several time starting at bottom of engine and work up. This will displace  any air . Finish off with the upper hoses.

Put on radiator cap.

 

Repeat .

 

Then drive a few miles and repeat.

 

Yes it's a PIA.

 

Did that on our 2003 D4D Yaris when I changed coolant at 10 years..

[Guest]

Sometimes it helps by having the car up on ramps or the front raised so that the radiator filler/cap is higher. Air migrates to the highest point, i.e. the radiator filler.

Also, as Michael suggests, gently squeezing the hoses, with the cap removed, can sometimes assist the "burping" process.

Or, at the extreme, the heater matrix is partially blocked or blend doors not functioning properly if that is the system used?

[Stivino]

Have a look at where the heater radiator is in relation to the rest of the system. 

If it is low, it will probably self bleed.

You could try disconnecting the heater hoses and flushing it through. 

[flash22]

The pipe tee's off to the intake, as above burp the system, given the age I would also check the heater control knobs as they are mechanical, the plastic can go brittle and/or the flap mounts can break - turning the knob does nothing