Morning all,

Got a bit of a problem with my 16 Plate tdi VRS.

Had a coolant loss issue for a while now, it wouldnt happen all the time, but sometimes when opening the bonnet I would find the coolant tank empty, or the fault would come up on the dash.

Ive now confirmed that the coolant only ever empties, after ive had the blowers on inside the car. Hot or cold, it doesnt matter.

I also found that it tends to come out of the expansion cap, so it seems to be over pressurising the system.

Took it to my mechanic (before I found it was emptying when using the blowers) and he changed the expansion tank and cap. But it is still loosing coolant, but only when the blowers are turned on.

Worth mentioning that when I turn the blowers to "HI" (hot), I dont think it gets as hot as it should, when the car is warm.

If I dont use the blowers at all for days at a time, the coolant level will not change. Turned them on halfway home yesterday, and the coolant tank was empty.

Also the temp gauge stays at 90 constantly once up to temperature.

Am I right in saying this is a heater matrix problem?

Thanks alot.

If you’re losing coolant via a failed heater matrix, your car will be wet inside. Best lift the carpets and check the front footwells for coolant. There might be an associated sweet smell (of the coolant) as well.

I’m struggling to see a link between a sealed liquid circuit and switching a blower fan on. Others will know better than me.

If it’s getting blown out through your expansion tank getting pressurised, it might be time for a sniff test and other investigations to confirm the integrity of your head gasket.

Gaz

Hi Gaz,

Thanks for replying.

I dont think the heater matrix is leaking, ive put more than 5 litres in the expansion tank now due to the issue, and I would have thought the carpet would be wet through and smelling by now. I think what is happening, is that the heater matrix is blocked, raising the pressure of the system for it to then go past the 1.6 bar limit on the cap and blow out the top. As I know this is a common issue, which has been reported a few times before.

However, like you say, I cant understand how turning the blowers on, links to an over pressure problem.

Does anyone have a schematic of the cooling system with all lines, valves and components?

May not be blocked matrix but air lock (hopefully) or exhaust gases if the HG has gone . If its the HG it will pressurise cooling system and also cause air/gas lock normally in heater matrix which would explain heaters not being very hot. Check the reservoir for bubbles and maybe a HG test plus look for white smoke at exhaust.

Alasdair

I started my Octy with a warning message and realised the coolant had drained completely via the coolant outlet, which perishes due to it's proximity to the turbo and therefore the heat produced. This was replaced, and all good from there onwards.

Another thought may be if the car has a coolant valve that opens when blower is on. It may be leaking.

Alasdair

23 minutes ago, Alasdair1 said:

Another thought may be if the car has a coolant valve that opens when blower is on. It may be leaking.

Alasdair

That’s a good point. Totally different engine (EA888 G3), but the most likely cause of my turbo’s demise back in 2018 was the coolant check valve reporting itself open, when it was actually closed. Painful experience that.

Gaz

Diagram of coolant system on EA288, TDI engine, Simply Clever, or Simply Complicated 😆

EGR cooler has a matrix that can leak.

5 hours ago, Gaz said:

That’s a good point. Totally different engine (EA888 G3), but the most likely cause of my turbo’s demise back in 2018 was the coolant check valve reporting itself open, when it was actually closed. Painful experience that.

Gaz

Wait until the water pump/therm housing goes. It is an issue on the TDIs too, but I don’t think it’s as prevalent.

6 hours ago, Noms said:

I started my Octy with a warning message and realised the coolant had drained completely via the coolant outlet, which perishes due to it's proximity to the turbo and therefore the heat produced. This was replaced, and all good from there onwards.

I replaced the coolant union at the back a few weeks ago. It’s prone to cracking and, as you said, gives little evidence due to the proximity to the turbo. I don’t think my car has a “leak” per se, but the coolant levels definitely aren’t 100%.

You don’t have a silica bag car do you @JMSkoda94?

Sorry for the late reply, works been busy and havent had chance to get on and update.

Paulski - legend, ill look at that later on.

So ive purposefully not used the blowers all week, and the coolant level has been fine.

Yesterday on my way home from work, I had the blowers on.

Checked level before leaving -OK.

Checked level when got home (16 miles) - OK.

Checked level when it was cold - Lost a little.

Checked level before leaving for work this morning - lost a little more (now on the max line, as i overfilled last week).

Checked when I got to work (16 miles) - empty.

When waiting at a roundabout I heard a gurgling noise behind the dash.

Proper head scratcher.