1.6 TDI Coolant Issues

[lhunter664]

A week ago I got a warning light on my 2013 Leon telling me to top up coolant. I pulled over right away and topped up the coolant (it was below the min line). After this I noticed the car had a loss in performance and a day later I couldn't get hot air through my A/C. I checked coolant the next day and it was nearly empty so I topped up and brought to mechanics. He had a look and said there is no obvious issue to him so used some stop leak and told me to keep an eye on it. The stop leak seems to have solved the losing coolant issue but I still can't get any hot air and noticing the car is working a bit harder. Engine/coolant temps are normal but I have also noticed some bubbling noises coming from the car after turning off.

The car is on 118k and has never had a water pump / timing belt so I have booked this for next month. Anyone have any ideas what this issue may be? Don't feel comfortable driving the car

 

[SRGTD]

The symptoms you are experiencing sound similar to those in the discussion topic at the link below, suggesting your car’s heater matrix could be blocked. The second post in the discussion thread by forum member @SuperV8 gives a good, succinct explanation of the problem;

https://www.seatcupra.net/forums/threads/occassional-loss-of-coolant-pressure-relief.476321/

I would personally avoid using stop leak type products as they can clog up the heater matrix and radiator core, adding to the problem(s) they are meant to solve.

 

[lhunter664]

Thanks for this

The symptoms you are experiencing sound similar to those in the discussion topic at the link below, suggesting your car’s heater matrix could be blocked. The second post in the discussion thread by forum member @SuperV8 gives a good, succinct explanation of the problem;

https://www.seatcupra.net/forums/threads/occassional-loss-of-coolant-pressure-relief.476321/

I would personally avoid using stop leak type products as they can clog up the heater matrix and radiator core, adding to the problem(s) they are meant to solve.

Thanks for the reply. Seems to match up with my symptoms. Any idea on how much I should expect to pay a mechanic for a replacement heater matrix? Not comfortable enough to do this sort of job myself.
Also would this type of repair be a matter of urgency? Have booked into a mechanics at the start of October for a timing belt change and wondering should I try get in before this?

 

[Seatmann]

Thanks for this

Thanks for the reply. Seems to match up with my symptoms. Any idea on how much I should expect to pay a mechanic for a replacement heater matrix? Not comfortable enough to do this sort of job myself.
Also would this type of repair be a matter of urgency? Have booked into a mechanics at the start of October for a timing belt change and wondering should I try get in before this?

I think the urgency depends on how cold you are lol. Seriously though, no idea on cost but most heater matrix tend to involve a fair bit of work dismantling the dashboard.

As for the timing belt, it's usually 140,000 miles on these 1.6 tdi engines. Used to be or every so many years but that's been done away with.

 

[SRGTD]

Thanks for this

Thanks for the reply. Seems to match up with my symptoms. Any idea on how much I should expect to pay a mechanic for a replacement heater matrix? Not comfortable enough to do this sort of job myself.
Also would this type of repair be a matter of urgency? Have booked into a mechanics at the start of October for a timing belt change and wondering should I try get in before this?

Cost of replacing the heater matrix will vary depending on a) whether you’re using a main dealer or an independent and b) whether or not the dashboard is removed to gain access to the heater matrix (Seat’s official recommended procedure involves dashboard removal). If Seat’s official recommended procedure is followed, then the labour costs associated with dismantling the dashboard could add significantly to the overall cost. There are forum members who’ve replaced the heater matrix themselves with the dashboard in situ, so it’s not necessary to remove it.

Assuming it is your heater matrix that’s blocked, until you get it changed I would recommend checking the coolant regularly and topping up with VAG approved coolant as necessary. As forum member @SuperV8 said in the discussion topic at the link I posted previously, over-pressurising of the coolant following a DPF regeneration increases the chances of coolant loss, so better to be prepared IMHO.

EDIT; IMHO it’s important not just to replace your car’s heater matrix if it’s blocked, but to eliminate what caused it to become blocked in the first place. If not, there’s a good chance the replacement matrix might also become blocked.

With this in mind it would be worth checking to see if you have the little ‘tea bag’ of silicate in your car’s cooling system expansion tank. If you do, be aware that there have been instances of these splitting and silicate ending up in the heater matrix, blocking the flow of coolant, so that could’ve been the initial cause of your problems - see discussion thread at the link below;

Removing silica bag from coolant header tank

Just a wee thread about how easy this is to do. Since my wife's Audi A3 bag burst blocking up the heater matrix we are now looking a big bill to replace the matrix and everyone i speak says that it's not even a guaranteed fix since the silica already in there is difficult to get rid of and will...

www.seatcupra.net

Another possible cause of a blocked heater matrix could be residual casting sand in the engine block from the original casting process when it was manufactured, and that sand working its way around the cooling system into the heater matrix over time.

Whatever the cause, ensure the cooling system is completely flushed through before the new matrix is fitted.

 

[MartinThorn]

No hot air does sound a bit like the heater matrix is blocked (could be 'natural' debris build up over time or silicates from the bag in the coolant tank).

I also recently had coolant loss and no hot air on drivers side so I replaced the heater matrix (myself due to astronomical garage quote) which fixed the problem:

DIY Heater Matrix Change - some teething problems but sorted in the end

Hi, Just done a DIY heater matrix swap on my 2.0TDI FR (usual problem of gummed up matrix causing coolant loss and poor heat out of some vents). I'll post some pics/info about that later this weekend.. However finished putting it all back together and just as I was about to celebrate no leaks...

www.seatcupra.net

I would say that my car had no loss in performance - not sure why that would happen. Speculation warning (I'm not a professional garage mechanic!): Also not sure that the 'stop leak' was a good idea as that might clog up the heater matrix further - it could also be that the coolant loss 'stopped' only because your car has not been through a DPF cycle? In any case as I said do bear in mind I'm not a garage mechanic here!