Heater box blowing lukewarm

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Ryan_mag

Member
Posts
26
Location
Northern Ireland
1992 Defender200tdi heater only blows luke warm and not much power even though the motor appears to be working fine. I have fitted a bilge blower from a boat to sort the power problem but it is still only blowing what seems like luke warm air

So far I've fitted a new heater matrix and replaced the seal between the heater box and bulkhead and still only minimal difference Even after the landrover gets up to full heat. Also both pipes going into the matrix are red hot.

Anyone any ideas what could be the problem? Tia
 
Is your heater box flap adjusted so it goes over all the way so nothing diverts past the heater matrix?

Is your coolant level ok? Do you have a air lock at the top of the heater matrix?
 
Replace the rad plug with a self-bleed one from a domestic radiator - yes, really ...

Back flush the heater matrix and re-seal the flappy direction doo-dahs ...

There's a write-up on here somewhere ... an adult will be along shortly to help ... @The Mad Hat Man
 
You sure the heater controls at the dash are working properly? I had a similar problem and the heater control wasn’t clicking onto high
 
Heater controls are definitely working. Will give bleeding it a go what size self beed valve do I need? Do I need to bled the matrix separately aswell or will it be bad at the same time?
 
Ryan_mag said:
Heater controls are definitely working. Will give bleeding it a go what size self beed valve do I need? Do I need to bled the matrix separately aswell or will it be bad at the same time?
Click to expand...

What I mean is have you tested the fan to know it will operate at all speeds and then checked that the heater control make this happen? If so then your loss of power has to be an air leak or the baffles are not opening and closing properly.

If both pipes going into the matrix are hot then unlikely you have a significant air lock.

My money is still on the controls - either the two cables to the box or the one that controls the resistor.
 
My heater was crap, fan never seemed to do the job, added bilge blower no better, replaced fan and removed bilge blower and ll is good again, well not good but passable!
 
Check for air leaks around the heater unit itself, the foam degrades and then any 'hot' air blows through the gaps and into the engine bay.
 
Thanks for all the help so far!

Tried parking on a hill and running for about 40 mins with the radiator plug off and going to buy a self bleed valve but still not difference

All heater controls are definitely adjusted properly now and the box to bulkhead seal was replaced when I changed the matrix and its sealing correctly. Tbh the fan is working deadon I think im just being fussy.

However it's still only blowing like warm air. Both pipes seem red hot from heater matrix to me it seems like the bottom of the matrix is airlocked so the water is only getting into part of the matric then flowing out again.

Other things: landrover build temp normally and guage sits bang in the middle and the thermostat was replaced 500 mile ago along with a full coolant flush

Anyone any other ideas?
 
Ryan_mag said:
Thanks for all the help so far!

Tried parking on a hill and running for about 40 mins with the radiator plug off and going to buy a self bleed valve but still not difference

All heater controls are definitely adjusted properly now and the box to bulkhead seal was replaced when I changed the matrix and its sealing correctly. Tbh the fan is working deadon I think im just being fussy.

However it's still only blowing like warm air. Both pipes seem red hot from heater matrix to me it seems like the bottom of the matrix is airlocked so the water is only getting into part of the matric then flowing out again.

Other things: landrover build temp normally and guage sits bang in the middle and the thermostat was replaced 500 mile ago along with a full coolant flush

Anyone any other ideas?
Click to expand...



Wont be air in the bottom of the matrix as I think both pipes come in the top, and as air rises?

Compared to any normal modern car the td5 and earlier heaters are pure crap.

What temperature stat did you fit?

The temp gauge is a very rough device and will stay in the middle from about 70 to 90 degc and I can say from experience 70 isnt enough heat for the heater to work well enough, 85/90 is what you need.
 
It's totally usual - almost standard - for the heater matrix to get a bit clogged up over the years. Back flushing sometimes works, but often a replacement is needed. As well as this, an old heater box leaks the precious warm air like a sieve and lets cold air mix with it no matter what position the lever is in. I found flushing the matrix worked, and blocking off the bypass (that lets cool air flow past the matrix) with foam camping mat worked well. You also need to look inside the dash - the hoses sending air to the screen often go astray. These few things and a bilge blower give me enough heat to clear the screen fairly quickly, and keep the inside warm on a run.
 
lynall said:
Wont be air in the bottom of the matrix as I think both pipes come in the top, and as air rises?

Compared to any normal modern car the td5 and earlier heaters are pure crap.

What temperature stat did you fit?

The temp gauge is a very rough device and will stay in the middle from about 70 to 90 degc and I can say from experience 70 isnt enough heat for the heater to work well enough, 85/90 is what you need.
Click to expand...

Not sure what temperature I just got it from the landrover parts supplier near me. What temperature would u reccomend fitting? Is there a way to test what temperature she is actually at I've one of them infrared thermometers if thats any help?. Could my water pump be causing the probelm either it dosent seem to leak but just a thought
 
zeaphod said:
It's totally usual - almost standard - for the heater matrix to get a bit clogged up over the years. Back flushing sometimes works, but often a replacement is needed. As well as this, an old heater box leaks the precious warm air like a sieve and lets cold air mix with it no matter what position the lever is in. I found flushing the matrix worked, and blocking off the bypass (that lets cool air flow past the matrix) with foam camping mat worked well. You also need to look inside the dash - the hoses sending air to the screen often go astray. These few things and a bilge blower give me enough heat to clear the screen fairly quickly, and keep the inside warm on a run.
Click to expand...

I've just fitted fitted a new matrix so can't be that! I agree I think there is air leaking around the dash but even if I remove the passenger side bottom plastic air vent and look in I can see the matrix clearly but the air is still only luke ish. Was playing with it earlier there and noticed that it seems to blow warm ish for a bit, then goes cold again, then eventually gets warmer?
 
Ryan_mag said:
I've just fitted fitted a new matrix so can't be that! I agree I think there is air leaking around the dash but even if I remove the passenger side bottom plastic air vent and look in I can see the matrix clearly but the air is still only luke ish. Was playing with it earlier there and noticed that it seems to blow warm ish for a bit, then goes cold again, then eventually gets warmer?
Click to expand...
Not the matrix then, good. Block off the matrix bypass with a bit of foam, seal around the matrix so that all the air has to go through it and seal around where the matrix pipes enter the heater box. You could even use duct tape as a temporary measure for that one.
 
Ryan, have just read this thread. It does appear your problem lies within the heater itself/water pump circulation volume [ability to pump to end of circuit, the heater matrix]. From above,I'd suggest you remove the control cables from the heater/heater flaps...then, with engine at std operating temp turn fan on full and manually open the heater diverter flap. This proves both of these functions are working correctly. If still poor heat it will be one of three things...

1. there's a blockage in the engine somewhere that's causing poor water flow[high flow resistance] into the heater matrix [this can still happen even with hot temp to both matrix pipes] and the water pump cannot supply enough hot water through the matrix at the req'd water volume/heat.
2. you are losing heat through the heater box within the bulkhead area and/or through the heater distribution pipes [recheck all heater seals]
3. your fan speed is too low :. poor ability to txfr heat into the cockpit - in order for the heater fan to give good airflow it needs good electricity :. have you 1. high resistance/part short in the 12v supply? [bypass with new known 0 ohm cable], 2. does the heater fan motor have a genuinely good earth contact, if not the motor output will be low even though the fan will appear to be working [run a new/proven direct earth cable]

The Landy heater design is, like many classic cars, very poor. Previously, I've rebuilt heater boxes with the v8250 patented method of 1. an uprated heater matrix, 2. fit reflective insulation material to the inside/every surface of the heater box, 3. cover the outer of the heater box with black self adhesive insulation. Providing your air and water flows are correct/good, the above mods give superb results; even on old MKII Jaguars with have appalling heaters.

Hopefully the above will help you find the fault and give a simple upgrade to improve your heat output...
 
v8250 said:
Ryan, have just read this thread. It does appear your problem lies within the heater itself/water pump circulation volume [ability to pump to end of circuit, the heater matrix]. From above,I'd suggest you remove the control cables from the heater/heater flaps...then, with engine at std operating temp turn fan on full and manually open the heater diverter flap. This proves both of these functions are working correctly. If still poor heat it will be one of three things...

1. there's a blockage in the engine somewhere that's causing poor water flow[high flow resistance] into the heater matrix [this can still happen even with hot temp to both matrix pipes] and the water pump cannot supply enough hot water through the matrix at the req'd water volume/heat.
2. you are losing heat through the heater box within the bulkhead area and/or through the heater distribution pipes [recheck all heater seals]
3. your fan speed is too low :. poor ability to txfr heat into the cockpit - in order for the heater fan to give good airflow it needs good electricity :. have you 1. high resistance/part short in the 12v supply? [bypass with new known 0 ohm cable], 2. does the heater fan motor have a genuinely good earth contact, if not the motor output will be low even though the fan will appear to be working [run a new/proven direct earth cable]

The Landy heater design is, like many classic cars, very poor. Previously, I've rebuilt heater boxes with the v8250 patented method of 1. an uprated heater matrix, 2. fit reflective insulation material to the inside/every surface of the heater box, 3. cover the outer of the heater box with black self adhesive insulation. Providing your air and water flows are correct/good, the above mods give superb results; even on old MKII Jaguars with have appalling heaters.

Hopefully the above will help you find the fault and give a simple upgrade to improve your heat output...
Click to expand...

How would I check/test for a blockage or is it worth just changing the water pump to start for all the price it?

Is there an in and out pipe on the matrix or does it not matter which way it is plumbed in?

Thanks again for the help
 
Ryan_mag said:
How would I check/test for a blockage or is it worth just changing the water pump to start for all the price it?

Is there an in and out pipe on the matrix or does it not matter which way it is plumbed in?

Thanks again for the help
Click to expand...

It doesn, t matter which way round the pipes are. Disconnect them both and put a hose pipe on it and see what happens
 
Rodeo Joe said:
It doesn, t matter which way round the pipes are. Disconnect them both and put a hose pipe on it and see what happens
Click to expand...

This, there's a need to know that there's good flow rate and that there's input flow AND return flow. If an engine has a blockage within the the water galleys there's the risk that the flow rate to it's furthest point of heat use [the heater matrix] will not get enough water flow :. thermal store, to give enough heat output from the heater matrix to provide enough heat irrespective of the fan air volume. I've only seen this happen once and it took me an age to fault find

ps when isolating from the matrix it's worth keeping the pipes on back of engine an adding a tap to each - this enables testing of water flow, one should be full flow, the second near zero flow.
 
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