No heating into cabin

Tomscar

Member
Hi folks, I have been round all the threads and can't find an answer to this issue, maybe some one has experienced it and can point me in the right direction.
My car is a 1.4 SE petrol with a BBY engine.
There is no hot air into the cabin at all ... the problem was a gradual build up, I noticed that the air from the vents wasn't as hot as it used to be during the cold weather and now it only blows cold air. Reading other threads I suspected it was the thermostat and or the sensor. I don't have VCDS so can't scan for faults.

What I've done so far:
I changed the thermostat housing yesterday as there was a slight leak from the junction with the 'death pipe' and also from where it meets with the engine block.
No leaks now, so there is a new thermostat and temperature sensor installed as part of the kit.
Temperature is getting to and sitting at 90 degrees on the dashboard readout.
The bottom radiator hose is getting hot when the thermostat opens.
All the vents and combination of vents feel like they are working and blow with plenty of force.
The pipe that feeds the heater matrix from the thermostat housing is getting hot but the return pipe is still cold.

I'm guessing at an airlock but can't see anywhere that you can bleed the matrix.

I've had the engine running today for about fifteen minutes with the expansion cap off looking for air bubbles but all I can see is a steady flow back into the tank.

So, kind folks and with thanks in advance ... anyone come across this or give me any pointers ... no rush as I've got instructions from Mrs B to cut the grass ?
 
Just an idea, may not be practical, but seems to me that the matrix needs checking out for a blockage. Could a garden hose be fitted to the matrix inlet, ans an open piece of hose to the outlet? If the hoses could be clamped tight, (mole grip or similar) before starting, coolant loss could be minimised.
See what others think. Probably not realistic, if so, sorry.
Mac.
 
Climate or manual? Manual suspect heater valve, blockage or incorrect coolant use. You say you have ran it with the cap off, did the fan kick in? Replace the cap and take it for a run. When you get back let it cool and check the level. There are some bleed valves in the main hoses but they vary in number between the different models.
 
Just an idea, may not be practical, but seems to me that the matrix needs checking out for a blockage. Could a garden hose be fitted to the matrix inlet, ans an open piece of hose to the outlet? If the hoses could be clamped tight, (mole grip or similar) before starting, coolant loss could be minimised.
See what others think. Probably not realistic, if so, sorry.
Mac.
Thanks Mac, I will certainly give it a go as there is enough access to remove the pipes 'easily', I think I'll try the outlet side first ... it feels almost solid when the engine is running and maybe air locked, failing an air lock I will try flushing it through with a hose pipe and see what happens ... I will post the result, hopefully tomorrow. Thanks again Mac.
 
Thanks Mac, I will certainly give it a go as there is enough access to remove the pipes 'easily', I think I'll try the outlet side first ... it feels almost solid when the engine is running and maybe air locked, failing an air lock I will try flushing it through with a hose pipe and see what happens ... I will post the result, hopefully tomorrow. Thanks again Mac.
Good luck!
Mac.
 
Climate or manual? Manual suspect heater valve, blockage or incorrect coolant use. You say you have ran it with the cap off, did the fan kick in? Replace the cap and take it for a run. When you get back let it cool and check the level. There are some bleed valves in the main hoses but they vary in number between the different models.
HI Audifan, it didn't seem to make any difference, manual or auto ... just blowing cold air and I've tried again, thermostat working and all the hoses get hot apart from the return pipe back to the thermostat housing.
There is a flow back into the reservoir from the top pipe and appears to run freely without bubbles.
The fan is kicking in when I switch the heating controls to on and also kicks in when I lower the temperature control.
I have only ever used the recommended coolant sold by Audi, currently G13 and topped up with straight tap water after changing the housing yesterday but will drain and add fresh coolant when I'm certain there's no leaks. The coolant in the reservoir is clean and still pink but will be under strength at the moment.
The return pipe feels solid when the engine is running whereas I can squeeze the warm feed pipe.
Can't find any bleed valves anywhere yet!!
Thanks for your input and I will take it for a run tomorrow and see what happens to the levels ... I will post the result
 
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Hi Audifan ... Climate Control

Climate Control.jpg
 
A VCDS scan would help. Be aware you will get loads of HVAC error codes. Get down into the passenger footwell and look up behind the glove box. Have some one else with the engine running slowly press the temp up button all the way to HI then temp down all the way to LO. You should be able to see the temp control flap move between the 2 extremes. Do this 4 or 5 times and make sure it does go to all extremes. If all ok then good chance blockage or air. Take it for an "Italian tune up". Does your radiator fan run at low speed when you switch the climate on. It should then as the engine temp gets hot second speed will come on ( 3rd speed if it gets really hot ). Climate may require re-gassing.
 
Thanks Audifan, I will give that a go tomorrow and try and get to the bottom of it.
Basically, I have a few things to go at now and hopefully it will be straight forward.
I have just checked the return pipe from the matrix now the engine is cold and it is no longer solid ... it felt solid when the engine was running and the pipe remained cold.
Not sure if the fan was running at different speeds but will check that tomorrow also
I was having a look online at the heater matrix, would I be right in thinking it is just an open ended radiator that simply allows water to flow in and out?
 
Yes just a standard water air heat exchanger. Need to know if climate is blowing very cold on LO as cold still be a low gas problem although should not stop HI heat. There is a coolant regulator valve ( hopefully that means more than just the thermostat ) according to the schematics. Presumably this can control the hot water flow. Unfortunately I do not know where that is in the 1.4 petrol cooling system, but is does look a possibility if the valve was not opening when required, jammed or failed.
 
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I tried to help @Kleynie with a very similar sounding problem in this thread.


Unfortunately can't say if this was the problem or not.
 
Good afternoon folks ...
Thanks Mac, I've back flushed the heater matrix, a simple enough job with a garden hose pipe as you suggested and it runs free in both directions, hopefully that means the matrix is still okay.
Checked both hoses while I was at it and no blockage there.
All connected up again and still only one of the pipes from the matrix is getting hot, baffling me at the minute and still assuming that it is just an in and out box with no valves, I was able to flush water through in both directions.

Going out now to do the checks suggested by Audifan.

Just a question if anyone else has also picked up on the thread ... looking at the diagram below, I have attached the pipe from the back of the thermostat housing, No. 8 on the drawing, to the right hand one of the two pipes that go into the bulkhead ... I didn't take a picture when I stripped it down and assumed the pipes would only go back one way but now I'm not sure if they are the right way round ... would anyone with a 1.4 BBY engine know if the rubber pipes cross over or if the right hand one of the bulkhead pipes is the feed in and the left the return back to No.11 on the thermostat housing?
Thanks for your time everyone, it is much appreciated.


Coolant Regulator.jpg


Feed and return pipes for the heater matrix at the bulkhead.
Heat Exchange Pipes.jpg
 
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Just found an online manual Audi Self Study Program 240 -

Looks like I've reinstalled the pipes the wrong way round.
If I've interpreted the drawing correctly then the left hand pipe when looking at the bulk head from the front is the flow into the heater matrix and should connect to the thermostat housing from No.8 and the right hand is the return to No.11
Back out to try that next ...
Heat Exchanger.jpg
 
The first post suggested that there was not too much wrong with the coolant circuit. If the temperature flap motor has failed (stuck on cold) there won't be much hot air in the car!

RAB
 
The first post suggested that there was not too much wrong with the coolant circuit. If the temperature flap motor has failed (stuck on cold) there won't be much hot air in the car!

RAB
If the temperatur flap was failing like stuck on cold and no heat being dissipated into cabin, the coolant return pipe ought to be eqaully hot as the pipe to the heater.
But I understand its not?
And to my knowledge there Isnt a coolant valve that could restrict the flow .
To me it more sound like an unintended flow restriction (clogged up) in that part of the coolant circuit, or as discussed some air pocket.
I would had thought that the rinse through would have helped.
Sorry I have no super suggestions, but a LHD BBY outside the house if you want something compared.
 
The heater matrix is similar to a radiator in reverse, so lots of surface area to volume with narrow channels. Could be blocked, especially with the wrong coolant and an alloy head. Once blocked it would be difficult to unblock with no flow.

RAB
 
The heater matrix is similar to a radiator in reverse, so lots of surface area to volume with narrow channels. Could be blocked, especially with the wrong coolant and an alloy head. Once blocked it would be difficult to unblock with no flow.

RAB
@Tomscar has flushed the matrix, and it's clear. Matrix would (I think) get hot even if heater flap was stuck closed. There seems to be no flow through the matrix, despite the cooling system, apparently, being fine. As Kate Bush once said "it's a mystery"
Mac.
My mistake, it was Toyah Wilcox, not Kate Bush!
Mac.
 
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Thanks Rab and Joga ...
Heater matrix was flushed out in both directions earlier today and appears not to be blocked.
I had the pipes from the thermostat housing entering the matrix the wrong way around.
Both pipes are warm now but there is still not a great deal of heat from the vents.
I also checked the new thermostat while I was at it and discovered I have been sent the old style with 83 degrees opening temperature.
Started it up again after swapping the pipes around and now the engine management light has come on and no water is flowing back into the expansion tank ...
So what started out as a simple replacement thermostat housing has opened a can of worms.
Time to call it a day and have a look tomorrow again..
 
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