Ongoing Cabin Heat Issues Matrix

[Compo1]

Eh up

Thought id start a fresh thread as im a little bit miffed with cabin heat problems.

A couple of weeks back i switched out my heater matrix as i had no hot air, matrix was blocked when i tested after removal.

Flushed the system with DI water till it ran clear fitted a new Nissense matrix and replaced di water with g12 evo bleeding the system with VCDS.

Great heat until Thursday last week when vents got cold when blower was on full and heat set to HI.

Re bleed system with VCDS and there was no improvement, so yesterday i removed the new matrix and water flows freely through it, not blocked. Calibrated air direction flaps. I get hot air on a low blower settings, so for me the matrix just is not getting enough flow to keep the air moved on the max blower setting hot. Its not blowing water out of the header tank when it regens at this point.

So anyone know what the problem may be ?

I know there is an electric pump on the circuit, i thinks its the one near the oil filter TDI184. Is that right ? How to test this anyone know ? And there appears to be a heater control valve N82 in the circuit somewhere. Anyone know where that is located ?

 

[SuperV8]

i believe the electric pump (on the micro circuit) is only used on cold starts (when your main pump is shrouded) and when you shut your engine off - to keep circulating the coolant though the micro circuit (EGR) when hot.

When the engine is upto temp - it's your main coolant pump doing the pumping.

Are you sure your engine is getting upto temp? What are your oil temps?
Check your flow and return pipes to your matrix (you can feel them under the dash) the flow should be hot, and the return should be cooler as the heat has been removed by the matrix.

If your matrix is not blocked and you can hear your micro pump working when performing a system bleed - then I would say either your EGR could be blocked (reducing mirco circuit flow) or your engine coolant temp could be limited maybe by a stuck open thermostat?

 

[Compo1]

With the weather as it is water temp is at 90c with in car instrument panel in around 5-6 miles

Oil temp starts to approach 90c and above around 8 miles in to a b road journey mainly 40mph. Even with the oil temps of 90c and above vents got cold when blower was on full and heat set to HI.

It is baffling me im sure the motor flaps are working as they should well reasonably convinced i may have to revisit that. So that left the heater support pump but now its doubtful that is the issue as you say this is not active when car is up to temp which make total sense.

So this leaves a heater control valve N82 restricting flow to the matrix and im not sure it even has one . The hot water flow is not enough to keep the air moved on the max blower setting hot.

I wonder what N489 valve role is ?

So your point on the EGR been blocked how do a prove that either way ? Disconnect the water pipes and check the flow ? I can see that been fun

Thanks for your suggestions mate

 

[SuperV8]

With the weather as it is water temp is at 90c with in car instrument panel in around 5-6 miles

Oil temp starts to approach 90c and above around 8 miles in to a b road journey mainly 40mph. Even with the oil temps of 90c and above vents got cold when blower was on full and heat set to HI.

It is baffling me im sure the motor flaps are working as they should well reasonably convinced i may have to revisit that. So that left the heater support pump but now its doubtful that is the issue as you say this is not active when car is up to temp which make total sense.

So this leaves a heater control valve N82 restricting flow to the matrix and im not sure it even has one . The hot water flow is not enough to keep the air moved on the max blower setting hot.

I wonder what N489 valve role is ?

So your point on the EGR been blocked how do a prove that either way ? Disconnect the water pipes and check the flow ? I can see that been fun

Thanks for your suggestions mate

The N82 valve - is the shroud on the electro mechanical main coolant pump. Which should move in or out depending on cold start, these can get stuck but I would expect if it was stuck closed so there was no flow from the main pump then you would also have an over heating engine! so I would presume as you aren't over heating - and you get upto temp speedily like my car this pump/valve is working fine.

This leaves the EGR cooler on that micro circuit! They also have flow and return connections so you could check the flow through the cooler - but the trouble is getting to it! down the back of the engine

I would just triple check the flaps are working before tackling the EGR cooler.

 

[Compo1]

This leaves the EGR cooler on that micro circuit! They also have flow and return connections so you could check the flow through the cooler - but the trouble is getting to it! down the back of the engine

I would just triple check the flaps are working before tackling the EGR cooler.

Yeah seen the location its a scary place that

As the egr cooler is on the same low temp circuit as the Matrix would i not get away with checking the flow through the egr cooler by disconnecting the bulk head matrix pipes and sending water through those obviously not in the matrix direction but towards the block. ?

 

[SuperV8]

That might work - though only one of the matrix pipes goes to the egr cooler - the other egr cooler pipe goes to the head.

 

[Compo1]

Well i thought i would close this problem and show you the cause.

My heater support pump and pipework to and from it was full of this stuff. See pic. It is neither gel from the bag it's not had one for 5 years or casting sand. Its like a brittle, compacted salt.

Ive spent the last day and a half removing pipework on the low heat circuit, including the metal ones to blast them out.

What a job I hate cars !

Anyone come across this ? I'd love to know what and how?

 

[SuperV8]

Well done on finding the cause!
Strange - has anyone ever put the radiator 'stop leak' crap in?

 

[Compo1]

Well done on finding the cause!
Strange - has anyone ever put the radiator 'stop leak' crap in?

I doubt it. ive owned the car from just before it was 3 years old with 21000 on it. Its a 2014 model. I've maintained it meticulously, well before schedule. It's been faultless till this, now sat at 64000.

I do everything on it but the timing belt and thats not down to know how or capability more time constraints.

Ive had the timing belt done by a VW trained vag specialist twice in that time. And i don't think its a coincidence, just a month after it's last change was when it started loosing cabin heat.

Could the mixing of two different coolant types cause this ? Its the only thing i can think of !

 

[SuperV8]

Ive had the timing belt done by a VW trained vag specialist twice in that time. And i don't think its a coincidence, just a month after it's last change was when it started loosing cabin heat.

Could the mixing of two different coolant types cause this ? Its the only thing i can think of !

From Valvoline:
There are some combinations that can completely ruin your car. Mixing OAT and IAT coolants can be detrimental. What is OAT coolant doing when mixed with IAT is turning the auto coolant fluid into a gel that can clog the cooling system and cause the engine to overheat. Removing this paste will take a lot of flushing and even cause damage that costs more than you realise. The same can happen when mixing propylene glycol and organic acid.

What coolants have you used?

 

[Compo1]

From Valvoline:
There are some combinations that can completely ruin your car. Mixing OAT and IAT coolants can be detrimental. What is OAT coolant doing when mixed with IAT is turning the auto coolant fluid into a gel that can clog the cooling system and cause the engine to overheat. Removing this paste will take a lot of flushing and even cause damage that costs more than you realise. The same can happen when mixing propylene glycol and organic acid.

What coolants have you used?

Well ive no idea what he used when the last timing belt change was done when the heat started to disappear. He did tell me he used G12+ Evo so when i did the matrix i used Holts HAFR0006B g12 evo i understand that is oat.

I did do 2 flushes with di water before swapping the matrix

 

[SuperV8]

Well ive no idea what he used when the last timing belt change was done when the heat started to disappear. He did tell me he used G12+ Evo so when i did the matrix i used Holts HAFR0006B g12 evo i understand that is oat.

I did do 2 flushes with di water before swapping the matrix

The various VAG coolant types are all miscible - so if its had only either G12, G13 or G12+ these can be mixed so I don't think this could be the problem.

 

[Compo1]

It's going to remain a mystery this one then.

Annoying

 

[SuperV8]

Bizarre.
Maybe after the last timing belt change they used some sort of chemical coolant flush - which has reacted badly?

This is an interesting comment from another VW forum regarding; Crystallization and soot throughout coolant system

​

The EGR duty cycle is too much now post fix, so it "cooks" the coolant's additives out of suspension in the EGR cooler, and the next stop is the heater core, so it clogs up.

Not sure if true - but sounds plausible!

 

[Tony .s]

i believe the electric pump (on the micro circuit) is only used on cold starts (when your main pump is shrouded) and when you shut your engine off - to keep circulating the coolant though the micro circuit (EGR) when hot.

When the engine is upto temp - it's your main coolant pump doing the pumping.

Are you sure your engine is getting upto temp? What are your oil temps?
Check your flow and return pipes to your matrix (you can feel them under the dash) the flow should be hot, and the return should be cooler as the heat has been removed by the matrix.

If your matrix is not blocked and you can hear your micro pump working when performing a system bleed - then I would say either your EGR could be blocked (reducing mirco circuit flow) or your engine coolant temp could be limited maybe by a stuck open thermostat?

View attachment 45642

Hi all
I have exactly the same problem as you , I have Replaced water pump,thermostat,removed the matrix and checked it was clear, water temp 90deg and I managed to remove the silicone bag out of the header tank in tact reset the flaps I am at a loss to know what else to do, I have had this car from new it has 92,000 miles and always serviced at seat garage?????
Any suggestions would be greatly appreciated
Regards

 

[Compo1]

Hi all
I have exactly the same problem as you , I have Replaced water pump,thermostat,removed the matrix and checked it was clear, water temp 90deg and I managed to remove the silicone bag out of the header tank in tact reset the flaps I am at a loss to know what else to do, I have had this car from new it has 92,000 miles and always serviced at seat garage?????
Any suggestions would be greatly appreciated
Regards

The matrix can still flow reasonably well with a couple of the channels totally bloke causing the low heat circuit to over pressure or not heat the cabin.

So what is your problem, you have no heat ? Blasting coolant out ?

If so despite the matrix flowing id replace it.

 

[Tony .s]

The matrix can still flow reasonably well with a couple of the channels totally bloke causing the low heat circuit to over pressure.

So what is your problem you have no heat ? Blasting coolant out ?

If so despite the matrix flowing id replace it.

I have warm air on the passenger and cold on the driver side, the matrix was very clean

 

[Compo1]

I have warm air on the passenger and cold on the driver side, the matrix was very clean

Warm or hot ?

I have after all my trial tribulations 65-69c across all vents on HI.

I take you have tried the vent motor reset ?

Have you looked at the actual motors under the dash to conform they open and close as you adjust the temp from cold to high ?

 

[Tony .s]

Warm or hot ?

I have after all my trial tribulations 65-69c across all vents on HI.

I take you have tried the vent motor reset ?

Have you looked at the actual motors under the dash to conform they open and close as you adjust the temp from cold to high ?

Hi
I would say hot , and I have done the motor reset I can hear the vents activating from side to side, I was under the impression that there is only one motor that is under the glove box.
Heater pipes at the bulkhead too hot to touch as are the pipes inside the cabin each side of the heater matrix.
I can’t get to the underside of the climate control panel without stripping out the centre console, this would be the only place left that controls the air flow.
I am at a loss what to do next
Regards

 

[Compo1]

Hi
I would say hot , and I have done the motor reset I can hear the vents activating from side to side, I was under the impression that there is only one motor that is under the glove box.
Heater pipes at the bulkhead too hot to touch as are the pipes inside the cabin each side of the heater matrix.
I can’t get to the underside of the climate control panel without stripping out the centre console, this would be the only place left that controls the air flow.
I am at a loss what to do next
Regards

There is a motor at either side and then another in the middle centre console i think, although ive never laid eyes on that one.