2005 Corolla heater fault

[Toyota heaterr]

  Corolla heater fails to heat up , on a one hour trip it will cut in for one or two minutes maybe two or three times . temperature indication normal . thermostat replaced ,coolant checked ,heater hoses through bulkhead cold these have been removed and the matrix flushed through initial red antifreeze and then high flow of clean water  Hot cold knob rotates freely opens and closes flap freely .air-conditioning is fine but still no heat .hi flow from the heater vents with no other problems  top and bottom hoses on the radiator get hot and the fan cuts in and cuts out and maintains normal temperature . Your help please.

[Notoyboy]

Has the heater failure happened since you did some work on the cooling system (eg. thermostat replacement)?  My initial thoughts would be that there could still be air in the heater matrix circuit.

[Toyota heaterr]

 No my wife just complained that the heater had stopped working so I was led to the thermostat by other threads. Then I changed the thermostat yesterday 

[Toyota heaterr]

 If it were an airlock how old Toyota get rid of it . Please.

[oldcodger]

Hi,

Sounds like you have covered everything  ...

If you have an air lock it normally will clear itself in a few days use; plus give it a few good revs to really 'flow' the water.

When you fill up, gently squeeze the rad  bottom hose  to push the water around.  

One point, your say " Hot cold knob"  don't you have the digital control in your 2005 model ?

The only things I would suggest is have you disconnected the  bulkhead pipes to the matrix  and checked that there is flow in and out of the engine block , you might have a blockage there ?

Also what about the water pump, is the aux belt good, not slipping , is the pump itself ok , not semi siezed, , still got enough power to drive water around hard enough to get into the heater.

 

 

 

[Toyota heaterr]

The heater control knob is rotary operation, operating a push Pull cable and a sound change indicates air entering from outside when rotated to cold . how do you check for flow at the bulkhead ? (when I disconnect the pipes coolant leaks from the hoses is that enough ). the right-hand hose as you look at the bulkhead is hot for the first 6 inches after exiting the block . the auxiliary drive belt was in a terrible state and split but was still operating satisfactorily.  I replaced this belt with the thermostat change,  there is no noise and auto tensioner works fine no slipping evident . Thank you for your help.

[oldcodger]

Hi,

Not sure how you would test with those rubber pipes disconnected from the bulk head,  I would be tempted to see if you can blow down one and get some flow out of the other to prove there is no blockage or connect a hosepipe if you have the parts, though that would dilute your expensive antifreeze.

It does sound like you have done everything right.. but am stumped as to what the fault is ....

[alan333]

1 hour ago, Toyota heaterr said:

The heater control knob is rotary operation, operating a push Pull cable and a sound change indicates air entering from outside when rotated to cold

Usually on cable operated systems the cable operates a simple open/closed valve on a hose in the engine compartment.  Check that your cable operates this valve, and that the valve lets water through when open.  

[Toyota heaterr]

If you’re confident that the rotary temperature control knob operates a valve do you know where the valve is , and how fresh cool air is admitted into the cabin if the temperature knob controls the valve? Thanks. P.s. I can see the push/pull cable operating to the rhs of the center console by the drivers footwell.

[oldcodger]

Looking in 2 books,  the post 2002 models  have heater flap control , no heater valve as most older cable operated motors once did.

Looking back at your posts, if after a good run your rubber hoses by the bulkhead are not both almost as hot then its not flowing though the matrix.

As you say you have done a flow test, either you may have disturbed some sediment or the new antifreeze has caused a reaction and its blocked things or you have a massive air lock.  If the old was T Red or Pink , what have you refilled with ?

On some models, like mine, there is an engine block drain tap just by the exhaust manifold which helps drain all the old stuff out,

I would say disconnect those rubber hoses again  and do a hose pipe or similar test on the matrix to ensure it is still  flowing ok. when you end the test, turn the flow off steadily so you can be sure no air is in the matrix, before reconnecting the pipes.

Also test those pipe back to the engine for flow, it could be a blockage in that area  or the rubber pipes themselves.

 

[alan333]

21 hours ago, Toyota heaterr said:

If you’re confident that the rotary temperature control knob operates a valve do you know where the valve is , and how fresh cool air is admitted into the cabin if the temperature knob controls the valve? Thanks. P.s. I can see the push/pull cable operating to the rhs of the center console by the drivers footwell.

Follow the cable at the engine side of the bulkhead - usually the valve is easy to locate.  I'm not certain how fresh cold air enters the cabin but at a guess the air enters the same way as heated air - passing through the matrix which is now cold since the hot water valve is closed.

[Toyota heaterr]

Sorry alan333 I think that is an unworkable condition, the grill where your wipers are is where fresh air enters , never through the matrix.

[Toyota heaterr]

OLD CODGER , top man a good run and we’re back to full heat . The thermostat was at fault and now all’s fine thanks for your input.👌

[alan333]

5 hours ago, Toyota heaterr said:

Sorry alan333 I think that is an unworkable condition, the grill where your wipers are is where fresh air enters , never through the matrix.

No bother, I obviously have very little knowledge. Obviously there’s no way fresh air could be obtained by an intake duct then flow through a matrix. 

And earlier you mentioned you had a new thermostat and both radiator hoses were hot. This would suggest the thermostat and pumping system were ok but the flow to the matrix was insufficient. Give us correct information next time and perhaps you’ll get better replies (certainly from me anyway). 

[Toyota heaterr]

Alan333 no problem.   “And earlier you mentioned you had a new thermostat and both radiator hoses were hot. This would suggest the thermostat and pumping system were ok but the flow to the matrix was insufficient.” That’s it in a nutshell and  “ Oldcodger” suggested an airlock in the matrix which cleared on a run . Thanks to all for your support.