Heater no longer working

[Cuppa]

The cabin heater in my '06 Patrol 4.2TDi has two heater hose pipes going to it through the firewall. Obviously one must be 'IN' & one must be 'OUT' .

Having just plumbed in my marine heat hot water service (heat exchanger inside a hot water tank), I find that whilst the hws gets hot & the engine temperature gauge sits in it's normal operating position, the cabin heater no longer works. Having checked I have found that all hoses get hot EXCEPT for the last section of hoses where they pass through the firewall to the heater. I removed the hoses thinking there may be an airlock but found coolant flowed out through them ok. Replaced the hoses, but still the heater didn't work. I am thinking that maybe I have been advised incorrectly as to which is the 'IN' & which is the 'OUT' connection & that maybe if I simply switch the hoses around that this may get the cabin heater working again (It was a very good heater working well prior to my adding to the system). This would work IF the heater is designed to only allow the coolant to flow in one direction.

Can anyone confirm whether it is usual for cabin heaters to only allow coolant to flow in one direction?

If it's not the only other possibility I can think of is that there may be an airlock in thr heater core itself - is this possible & if so what is the solution?

Thanks
Cuppa

[04OFF]

Hi mate, while i don't have a exact answer for you, and not really 100% familiar with your exact set-up, but a great way to make sure you have no air locks is to "back fill" the system.

You can get a 1/2 meter long bit of heater hose and a funnel that will feed/fit it nice and snug,(garden hose and a cut plastic bottle as a funnel can work) you then put this hose end onto your one side of your heater core, and raise the funnel high in the air.

The heater hose that you removed from the heater core, you need to raise up (or extend with more hose) in the air above any other part of the cooling system (this prevents all the water just running out with gravity)


Remove radiator cap, make sure the heater tap is not closed, then get someone to pour water down the raised funnel, when water comes out clean (no air) from any one hole, block off that hole/hose not letting air in,(this forces the water flow to other areas) still keep pouring water down the funnel untill no air is seen from any hole, you can also remove other hoses around the cooling system to purge air from any high spots or places you feel it may get trapped.


You could also use the hose and funnel method to bleed your hot water service individually first.



I used this method on Water cooled Turbo set-ups to purge the Turbo (Turbo sat higher than the engine) its basic, but works very well, i always had a small air bleed hole in my thermostat, you may have to do hoses on both sides of the thermostat if your thermostat seals 100% when closed.

[Cuppa]

Hi, I have now resolved the problem of the heater not working. It wasn't an airlock. The problem was that I had plumbed the calorifier (heat exchanger HWS) in incorrectly. I had plumbed it in in series with the heater as in diagram 1 & by the time the coolant had reached the heater it had insufficient pressure to push through the heater core, instead taking the less restrictive route back to the pump. Having realised this I re-plumbed the system so that the calorifier is now in parallel with the heater as in diagram 2. & all is good. I included the taps (manual inline heater valves from ebay) as I was unsure if I might need to choose between having a heater OR hot water. As it turns out they were unnescessary & both heater & HWS work well together, but the taps still serve the pupose of allowing me to isolate the calorifier section of the circuit, meaning there if there is ever any damage to the hoses I've run under the vehicle they can be shut off allowing us to keep driving in remote situations.

Cuppa