Golf GT TDI MK7 No heat from vents

[Candellara]

Hi All

Wife's 2013 Golf has suddenly developed a fault where there's not hot air coming from vents when temp dial is turned up full - just luke warm air


It's always been ok - just suddenly happened on a long run today. AC is fine and blows cold but when you turn temp up - only luke warm air.

Water pipes at bulkhead - one is hot and the return is luke warm.

Heater valve? Matrix? Not losing any water and car only done 40k miles

Anyone else had issues? Known problem?


Edit - Checked the coolant level and it's fine but water viscosity is very "sticky" (more so than regular antifreeze) - car has full VW service history. I've read that MK7 Golf's have a silicon bag in expansion tank that has a habit of leaking and clogging heater matrix ?

Edited by Candellara on Sunday 2nd December 16:16

[Candellara]

davebem said:

With the engine stone cold, remove the header tank cap and check you can see the silica bag in there and not split. You can see it because its a red-ish colour due the coolant. Failing that does it have climate? it might be worth seeing if there are any error codes to do with the sensors.

Will have a look in header tank. Had all of the codes pulled - nothing at all. Engine temps are perfect, temp flaps etc all operating ok. All seems to point towards clogged heater matrix which I find really hard to understand.

Car is low mileage, 5 year old car with full VW history - must surely be a design fault of this silica bag and the size of the channels within the heater matrix?

[Candellara]

rllmuk said:

I had exactly this in my wife's 2013 Leon (2.0 diesel 150ps). Vents stone cold. Replaced the heater matirx which was clogged up and the car gets warm way before it hits 90 now. Also changed the coolant at same time.

Heater matrix was about £100 new, with replacement coolant is a reasonably cheap job if you take on yourself.

edit: look here for more info: https://forums.seatcupra.net/index.php?threads/air...

Edited by rllmuk on Tuesday 4th December 17:38

Thanks. Pretty certain its the heater matrix and the dreaded silica bag leaking. Going to be flushed tomorrow to confirm and see if there's an improvement. Golf MK7 matrix is an all day job @£125 per hour (according to VW) _ matrix £220 so £1200 job it seems?

[Candellara]

What completely astonishes me is that after having the car serviced every year at VW, it's not part of the car's schedule i.e drain coolant and replace header tank

VW are aware of this issue as they've had to hand out new cars in the US because of this problem with the silica bag rupturing and clogging the cooling system.

Not once in 5 years have we ever been asked to change the coolant at VW as part of the service

[Candellara]

OK. An independent garage had a look. They reckon that they flushed the heater matrix and the car was ok for about 6 miles but then blocked up again.

I asked why they didn't drain the rest of the cooling system but I got a shrug of the shoulders. So, if they are telling the truth, we know that the matrix can be cleared and operable if the rest of the system doesn't recontaminate it.

Time to roll my sleeves up I think. Drain complete system, reverse flush matrix with hose (very low pressure I guess?) replace header tank and refill?

Any specifics regarding bleeding the cooling system on 2.0 TDI? or is it just the old fashioned way via header tank?

[Candellara]

OK. Car's been at VW for the day

They've 100% confirmed that it's a heater matrix blockage but they cannot say why :-(

It doesn't look as though the header tank silica bag has been compromised as the coolant is nice and clean rather than the murky brown it turns when the bag has split


£819 for VW to fit a new matrix but they've already said, they cannot guarantee that a new one won't block in the same way (well documented across internet and VW in the US had to give one owner a brand new car under the lemon law)

[Candellara]

OK. Another update.

Had some time so thought i'd have a quick look myself

Disconnected top and bottom hose from bulkhead and connected a hose pipe. Water instantly pouring from lower heater hose - no blockage.

Tried reverse flushing but it wouldn't so I assume there's a one way valve in the system?

Drove the car a few miles - nice hot air from heater.

So, i'll monitor the situation over the next few days. But, an independent and a VW main dealer have diagnosed matrix blocked - impossible as water flowed straight away and heater now hot.

Any idea's?

[Candellara]

Maybe one way valve temporarily got stuck open? I'm assuming there is a one way valve as it was impossible to reverse flush.

It would makes sense if there was a temperature controlled valve which opened and shut to ensure matrix was maintained at a certain temp to ensure cabin hot air?

[Candellara]

OK, Further update

50 mile drive today and the heater is still blowing warm / hot air

I'm frankly puzzled as to what was / is going on but it still makes no sense that two garages including a VW main dealer should diagnose the matrix when it's clearly capable of delivering heat to the cabin. A matrix is either blocked (as diagnosed) or it isn't

[Candellara]

Chris_W_ said:

Can anyone assist further on this? I have a 63 plate MK7 GTD that heater does not get hot and keeps loosing coolant. No sign of any leaks.

Thread resurrection time. After many months of the car being fine, the problem has reoccurred. I'm guessing that the silicant has blocked the matrix again. Anyone had any luck / insight into this?

I cannot see any coolant bleed valves on the mk7 2.0 tdi - any VW techs on here to share some insight?