Heater blows cold - read and tried everything :( Need help bigtime !

Joebrown69 · Feb 2, 2021

Hi all I'm new here. Need help big time!

I have a 2009 navara and the heaters inside haven't worked for a while so I've finally decided to get them fixed and f*** me what an ordeal this has become.

I initially took it to Nissan and they diagnosed a blocked heater matrix, and pressure test came back fine.

So I take it to my trusty garage he strips it down, unblocks matrix, replaced the rad (it was all gunked up), still nothing, then checks water pump and thats fine and finally replaces thermostat, still nothing! So then he takes the dash off and a door heater motor is broke so removes that but still no hot air!

He tells me that he has done everything bar the ECG cooler unit and asks has anyone worked on it and possible tubed it up wrong, and to my memory they haven't. He tells me to ask nissan for a diagram and if there is any known issues with ECG cooler units.

He tells me the flow going to the matrix is too low

Nissan tell me its Nothing to do with the ecg cooler and i need to take it back to them to look... so back to square one.

Also checked the solenoids/resistors and it ain't them apparently.

I'm not a mechanic but I have a decent understand of how things work.

Anyone have any information on what it could be?

My next step is to go Nissan again but its £50 diagnosis and if there isn't water getting to the matrix I'm sure it will come up the matrix is blocked again and they want another £120 to diagnose that...

Any help would be so so greatly appreciated!!

Old.Tony · Feb 2, 2021

The EGR cooler is directly in the flow path of the heater matrix inside the cabin, so it absolutely might be an issue!

Luckily there are a couple of things you can check.

Look at the EGR cooler (gold pipe that runs around the front of the engine, has two rubber hoses connected to the top). One of those hoses will run back to the firewall (this is the EGR Cooler Outlet), the other is connected to the side of the engine (EGR Cooler Inlet). Disconnect the inlet and outlet and pump water through the EGR cooler itself. If there's flow out the other side, you can ignore this component and move on. If there's no flow, this is your problem and there are two options. 1) replace the EGR cooler (if your EGR is still being used, this is suggested, but if you've blocked the EGR then who cares) or 2) if you've blocked your EGR, just put a joiner between the two hoses that went to the EGR cooler.

If that didn't fix it, you might check the flow through the inner matrix just in case. This is easy - that hose that came off the EGR cooler that heads to the firewall is the intake hose for the heater matrix. There'll be another hose coming from the firewall that heads back out to join up with all the others (connects to the thermostat housing). Undo this hose at a convenient spot and pump water into the inlet.

If those two checks don't provide an answer, you might slip a clear piece of hose into the EGR Cooler Outlet line and warm the engine up, watching that hose for flow. If there's no flow, it's possible that there's a blockage somewhere in the inlet side of the EGR cooler line (and perhaps in the block, the EGR Cooler Inlet hose should connect to the side of the motor, it might be blocked there).

Joebrown69 · Feb 3, 2021

Cheers that sounds perfect advice! I had a try to remove the tubes but it was a bit rusty and I was scared of snapping it and not being able to put it back on so going to relay this information to my garage and I'll let you know how it gets on!