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

[davebem]

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.

[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?

[rllmuk]

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

[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?

[DuraAce]

Candellara said:

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?

I guess the dash needs to come out on the mk7.

Take it to an indy though (if you aren't DIY capable). £1200+ for a heater matrix swop is crazy money IMHO.

[rllmuk]

I don't know how similar the Leon is to the MK7 but all I had to do was:

• remove the trim to passengers side of middle console
• remove panel under glovebox
• flip glovebox down (as if for pollen filter change - pinch clips in)
• remove air vent and motor

The matrix can then be slid out once the two pipes and cover have been removed. Top pipe clip slides off, bottom one is held on with bolt. I'd imagine, being VAG, it's similar it just depends what extra trim the golf has in the way.

[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

[rllmuk]

Yes, it is a farce and one that is very common among cars of this age across VW, Skoda and Seat. Is a flawed design with a simple remedy if built in to service schedule. Like you, our car has only ever been serviced by Seat according to their schedules but a fix is an astonishing bill if done via those same garages. You could take up with VW and see what they say?

[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?

[rllmuk]

Either take off bottom hose or out of header tank. I actually drained mine partially via the lower hose on the matrix with appropriate water receptacle, then lower hose for the rest.

I doubt you'll be able to flush it for anything than a short term fix - once clogged they tend to be scrap...

Edit: ah, you said bleeding - it's a pressurized system but I've always done it with the cap off. Just don't do it when it's hot!

Edited by rllmuk on Wednesday 5th December 16:56

[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)

[rllmuk]

£819!

Currently £110 for a matrix on EuroCarParts with discount code XMAS75.

[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

[JumpMan1980]

Hi - how did you get on with this? I’ve got the same issue !

[C. Grimsley]

Changed three matrix’s now at our garage on golfs, flushed the first one out and it was fine for a few weeks then blocked, it can be done with the dash in, takes about three hours.

My own gold on a 65 plate is stamrting to show the symptoms.

Carl

[JumpMan1980]

Perhaps you can help with my car troubles .. no hot air in cabin (warm only which tails off to cool after a few minuted) and mystery coolant loss - local garage and VW have both had a look, pressure tests, visual checks etc to no avail. Local garage reached end of their expertise and VW wanted £1100 to replace matrix/ flush coolant system and then check 'cooler' - way too much money to find out where this coolant is going? To be exact it's losing a header tank full every 7 days and I travel about 250 miles in that time ...

[Dicky300]

Hi, I've been going through exactly the same. This should be a recall. Hence lack of help from VW.
All I can add is there are various reducers and one way valves in the pipes.... One which reduces water to a pin prick. Theses will be easily blocked by the silicone sludge. And may stop back flushing. Any advice on flushing appreciated.. I've never seen so many pipes... I'm sure that will do it though.