Cabin Heater problems again.

[Charlie Farley]

Afternoon chaps.
Righty then, having spent all day messing around with the old bus and its lack of cabin heat, I'm still no further with resolving the problem.

So a bit of a flashback to a few months ago when I replaced the cam belt/water pump.
That task went straightforward enough with no probs and heating/cooling was ok afterwards, well i never tried it on full heat as it wasn't cold weather.
a few weeks later the heater started to pump out warm air and it would get cooler as the engine speed decreased so on idle it was just cool air.

I sort of put up with it for a while before it became a problem with defrosting etc, so used the approved method of bleeding and the problem went away, but it returned in force recently.
Thus far here's what i have done to try and resolve it.

Today I have run vcds and scanned the HVAC system and no faults were logged , so then did a full system check on the HVAC and all parts were tested and functioned correctly, I even saw the motor flaps moving during the relevant tests, so it's not that at fault.
water temp sits at 90 on the dash so did a live vcds on coolant temp and actual showing at 88 so it's not that.

The outlet from the heater matrix is cool again, so did another bleed and hot started moving around to the point it was really hot air coming out the vents, then it went cool again.
I'm at a loss to be honest, if I go for a drive with it on max heat setting it does blow out hot, but once you come to an idle it starts going cool again.

Can it still be an airlock?
How much air can get trapped in the system and how can it be removed?

For a second I really did consider whether the water pump was to blame but given the running temp is ok, that seems unlikely, but maybe possible I suppose.

If anyone can enlighten me more on this dilemma and how to resolve it, please do let me know.

Rob

 

[Garrett 69]

Possibly a faulty expansion bottle cap? If the system doesn't build and maintain pressure you will have these symptoms (coolant only works properly under pressure). Have you ever had any overheating issues?

 

[Charlie Farley]

Possibly a faulty expansion bottle cap? If the system doesn't build and maintain pressure you will have these symptoms (coolant only works properly under pressure). Have you ever had any overheating issues?

Thanks for the reply chap.
Overheating has never been an issue thankfully.
You have got me thinking now though. last year replaced my split leaking header tank with a new one, not an OE part at the time as I couldn't get one, it looked ok and fitted ok so just went with the flow.
The cap didn't seem to close the same as the OE tank though, just twisted with no firm clicking lock that I had with the OE tank, and it never seemed to have much pressure in the tank, I could get the cap off without much pressure even when hot.
Maybe there is a pressure leak around the cap as you say.
I was aware that the B7 has a pressurised system and to be honest, it can be problematic, but it just seems odd to have so many probs this time around that I haven't had before given I have drained down the system several times without all these problems in the past.
If I break it down in a timeline, the only thing that's is different is in fact the header tank.
I think the next step is to get a new OE header tank and cap and see if it gets pressurised and holds it.

Many thanks once again chap for the reply, sometimes a pair of fresh eyes is all it needs, it is probably the missing part of the equation .

 

[Charlie Farley]

There are a couple of upsides to my heater issue though.
At least I now know my climate control flap motors are all working ok and my thermostat is also functioning correctly.

 

[Fully]

Could it be a problem with the heater matrix

 

[Garrett 69]

If it were the matrix, I'd expect it to be leaking

 

[Fully]

If it were the matrix, I'd expect it to be leaking

just going from experience i had with my old A3.
When it was taken out it was full of a gunky substance that was stopping the heating from working properly

 

[Garrett 69]

just going from experience i had with my old A3.
When it was taken out it was full of a gunky substance that was stopping the heating from working properly

I see your point I'd expect higher than normal pressure with a blocked matrix though...

 

[Charlie Farley]

No leaks .
It does seem to be low pressure-related though, it would account for drop off in heat on idle, but almost spot on when driving at higher rpm.

 

[EnGeO]

Find a place with one of these cooling system cleaning machines, and i bet your problem will go away!

Enviado do meu SM-G781B através do Tapatalk

 

[8YARWY]

There are a couple of upsides to my heater issue though.
At least I now know my climate control flap motors are all working ok and my thermostat is also functioning correctly.

This is a problem on the Golf 7 as well (we have one) heater matrix can be the issue, and it doesn’t leak either if it’s faulty.

The OEM one has very narrow channels that can get gunked up, but the biggest killer of them is if the Silikat bag splits.


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[Charlie Farley]

So it's not the expansion tank cap, tried the new one-off my TT, same cap exactly and no change.
I've ordered a new tank and cap anyway just to eliminate both from the list of the possible, cheap parts as well so not too much to lose if it's no change after that.

I'm snowed under with work at the moment so don't have much time during the week, so might at the weekend disconnect the heater from both inlet and outlet hose connections and do a reverse flush, nothing lost and may help .

 

[Charlie Farley]

Find a place with one of these cooling system cleaning machines, and i bet your problem will go away!

Enviado do meu SM-G781B através do Tapatalk

Not sure I've seen that service offered in my location to be honest.

 

[Charlie Farley]

Logically thinking on this problem.
As i know the water pump is working ok, stat is working ok and the engine temp is correct and stable. The expansion tank and cap are pressure-tight and have no system leaks, I've checked the motor flap on the climate control and all working, so what's left, just the heater itself.
Whether the matrix is clogged, that remains to be diagnosed but it's the only item left in the loop.
So that's Saturdays project.

 

[Charlie Farley]

This is a problem on the Golf 7 as well (we have one) heater matrix can be the issue, and it doesn’t leak either if it’s faulty.

The OEM one has very narrow channels that can get gunked up, but the biggest killer of them is if the Silikat bag splits.


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No silicone bags fitted in the coolant system on B7's so that's off the possible list .
list of possible causes is prettywell down to 1 now.

 

[8YARWY]

No silicone bags fitted in the coolant system on B7's so that's off the possible list .
list of possible causes is prettywell down to 1 now.

If the flush doesn’t fix then look at Nissen heater matrix.
Bigger channels on the inside than the oem ones (some are made by Valeo which are crap)


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[Charlie Farley]

If the flush doesn’t fix then look at Nissen heater matrix.
Bigger channels on the inside than the oem ones (some are made by Valeo which are crap)


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Are they readily available ?

 

[Fully]

https://www.onlinecarparts.co.uk/nissens-1991639.html

 

[Charlie Farley]

Ok, a bit further on with this but still no real continuous heat at idle.
The header tank and cap were replaced this morning with no change at all, to be honest, I didn't this would be the problem having swapped the cap from my TT with no change.
Still this problem of lots of heat when driving, the more rpm the more heat, anything less than 1500 rpm and its just warm /cool, as soon as you drive its rudy hot.
I did a reverse flush of the matrix and it wasn't really conclusive, only clean coolant came out.
The new matrix I ordered arrived this morning but it was damaged, looks like it had been ordered before, wouldn't fit the car the buyer had and in the process damaged a lot of the fins, the lower hose fitting was damaged and would never be watertight, so not a good day .

still undecided if it s the matrix or an airlock still.
any thoughts.

It's doing my head in now, not an issue that has affected the old bus before even after several system drain downs.

 

[Charlie Farley]

I've even tried pressurising the header tank just enough to push any air upwards out of the heater matrix, with the hose bleed hole just open enough I had a continuous strong stream of water, nipped the clamp up again , topped up tank , still the same, Arghhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

 

[norad97]

I guess you ruled out the thermostat, could it be stuck half open? Just a thought as the more RPM maybe pushing more coolant around,
idle is less.

 

[Charlie Farley]

Evening Richard,
Stats fine as I did a real-time water temp check with vcds and the gauge said 90 and live vcds showed an actual of 89.
The engine warms up normally and holds heat normally, with no sign of overheating either.

Just annoying really, I'm having another look in the morning and it's still the same it can only be the matrix at fault.
Just need to wait for a replacement for the damaged one though.

 

[Charlie Farley]

Some marginally better news today, I have more heat on idle today, it's not 100% normal but a big improvement.

I'd thought I'd share a few pics of the so-called "new" heater matrix I received on Saturday.
Make your own minds up chaps but no way is that fit for purpose as new, should not have even been sent out.
I don't think there is one side that's not been bashed in and that's not in transit damage, someone has tried fitting this before and mullered it big time.
no new seals or foam strip either.

 

[norad97]

Some marginally better news today, I have more heat on idle today, it's not 100% normal but a big improvement.

I'd thought I'd share a few pics of the so-called "new" heater matrix I received on Saturday.
Make your own minds up chaps but no way is that fit for purpose as new, should not have even been sent out.
I don't think there is one side that's not been bashed in and that's not in transit damage, someone has tried fitting this before and mullered it big time.
no new seals or foam strip either.View attachment 248601View attachment 248602View attachment 248603View attachment 248605

Now that has been butchered, like put the old one in the box and sent it back.

I seen a bleeding procedure that you could try, if you have not already.
With the engine cold, Unscrew the expansion tank, take the cap off, lift and turn it vertically, higher the better,
pull back the pipe in the bulkhead, the one with the bleed hole, bleed out and watch for air, keep the tank topped up.

 

[r.curt]

Did you get to the bottom of this as I kind of have the same
Problem


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[Charlie Farley]

Nearly.
I have eliminated all possible causes except 1, all that is left is the heater matrix.
I have another one being delivered tomorrow.

To be honest, it's only very marginal now, pretty well hot on idle and boiling when driving so whether the matrix is still at fault or it was an air lock that is finally clearing, won't be clear until I fit the new one, then start all over again to bleed the air out.

 

[norad97]

Hi Rob, it sounds like its clearing. Might be worth just redoing the bleeding again.

 

[Charlie Farley]

The replacement heater arrived yesterday and is in perfect condition and complete, but, I won't need to fit it now.
The old bus is now back to its previous best with glorious heat on idle and all temp settings work spot on, so it was just an almighty Airlock, the heater wasn't clogged.
I was half tempted today to swap it over just because it was new, but then I thought, Why, so I won't mess with it now.

What I have learnt from this problem is this .
Airlocks in the heater matrix are a real bind and can take some messing around to shift, and not always that well.
Forget hanging the header tank up etc, the quickest and most effective method is to pressurise the header with a compressor or whatever you have to 10psi and just push the air out the top heater outlet.

Anyway chaps, a nice warm cabin again and happy days too.

cheers
rob

 

[Charlie Farley]

On reflection this evening , maybe worth fitting anyway.
I've paid for it so might aswell fit the new one, worse case I will have to bleed the system again but with my newfound method that may not be so bad this time around.
I'll have a think overnight and my frosties in the morning.

 

[Charlie Farley]

Just an update on this subject.
All is spot on now after a couple of weeks of problem-free heating etc and I opted to leave it all alone rather than fit the new matrix, the old adage, if it's not broken applied to this problem.

happy days chaps..
rob

 

[norad97]

Just an update on this subject.
All is spot on now after a couple of weeks of problem-free heating etc and I opted to leave it all alone rather than fit the new matrix, the old adage, if it's not broken applied to this problem.

happy days chaps..
rob

Then don't fix it, your right to leave it alone as the risk of more airlocks is a possibility.