Low Heat - blocked heater core?

[bonbon]

Seems like heat is much lower than in the past. Not only in idle but also while driving or when circulating air internally.
Thermostat, water pump and heater control valve solenoid are ok (and even if failed microswitch in behind heater control dial would leave the valve open).
I will try to remove any air in the water system and reverse flush the heater core.
Any other intelligent ideas?

 

[colb]

Could be stuck open thermostat how do you know yours is ok? Reverse flush would be a start then refill and bleed with front of car as high as you can get it so filler is highest point. A vacuum filler is great for refilling if you have a compressor to run it.

 

[Kenhayes247]

If you are going to refill and bleed the coolant system, one of the forum members recommended to me to remove the top right hose from the radiator and having undone the bleed screw from the radiator refill the coolant system through the hose. When full, re-attach the hose and continue to refill until coolant comes out from the bleed screw and the hose is full. Then bleed the system as per normal.

You shouldn't need to jack the front of the car up at all. For me, having done this several time already the success rate of not trapping air in the system has been 100%.

 

[Rudyrov]

I replaced the heater valve in my Z because it would not shut off, after that it worked ok for a bit and now has stopped.
Does anyone have the voltage values that should go to that valve or perhaps the thermostat controlling it?
I have seen those wonderful wiring diagrams but have not been able to find a troubleshooting guide.
Thanks!

 

[Nodzed]

Don't assume the thermostat is OK even if it's been replaced.

 

[bonbon]

I assume the thermostat is ok because the time it takes for the temp to rise and settle at 12 o’clock is as normal. (….about 5 mins of driving)

 

[bonbon]

Raised the nose and no air in the system. The heater control valve responds to external 12V (as microswitch in temp dial has failed)- so odds of being blocked or stuck closed is small.
So no now suspect a partially blocked core - will take a while - but will flush the core and hope it will then provide good heat. At 470k km - a flush of the core can’t be a bad idea.
Will update…

 

[bonbon]

Has anyone experienced a substantially blocked heater core and managed to flush it out and make good?

 

[Richard29]

Same issue on my old 2.0.
New thermostat sorted it.

 

[bonbon]

Please spell out what is the connection to the Thermostat?
I am experiencing that the pipe going into the core is hot and the outlet pipe is cool (and as the heater control valve is always open).
My assumption is that the core is partially blocked.

 

[Rudyrov]

You could try and run a good quality cooling system flush and after that you can flush the entire system and then flush the heater core separately by disconnecting its hoses and flushing it separately with a garden hose while observing the flow as you run water through it.

This would show you the flow characteristics of the heater core close up.
Hope that makes sense to you.

 

[Richard29]

The temp gauge on mine indicated cold all the time. So different symptoms to yours.

 

[bonbon]

Ok
Flushed the core - it was ok - a bit of muck but not blocked.
(Chinese) Heater control valve was activating BUT when open, plunger was floating and not fixed in open position - its bronze weight was weighing it down so it was partially restricting flow. The new one: the plunger is pulled up in a fixed position when open (no voltage applied) and full pyramid shape of plunger is visible.
New Chinese unit installed - I guess it will also screw up at some point.