Sep 12, 2019
9
0
Having a heating problem with my Leon, I've seen threads on this before but nothing as specific as mine.

2 days ago I had a low coolant warning on the dash, checking it revealed the coolant tank was almost empty. It was last checked a few weeks ago, so is very odd to drop so much so suddenly. I topped it up back to the max level, keeping an eye on it as it. Today I noticed that I've got little to no heat in the cabin. It has been taken for a 140 mile round trip on the motorway, so the engine has been up to temperature - coolant reading 90C as usual. (I have the 2.0 TDI 150PS)

Both heater matrix hoses in the engine feel warm to the touch, making me think heat is flowing into the heater matrix itself. I have tried the simple HVAC flap reset (
) thinking it could be a flap stuck, but with no luck. Its a 2013 Leon FR Technology, so has the dual zone climate control - both sides are blowing cold air no matter what the temperature. There is a slight amount of warm air when set to high, however not enough to feel unless you have your hand in front of the vent. Squeezing the heater hoses to get rid of any air in the system hasn't worked either.

Any ideas?
 

Jay5959

FR 184
Apr 26, 2020
444
221
Having a heating problem with my Leon, I've seen threads on this before but nothing as specific as mine.
2 days ago I had a low coolant warning on the dash, checking it revealed the coolant tank was almost empty. It was last checked a few weeks ago, so is very odd to drop so much so suddenly. I topped it up back to the max level, keeping an eye on it as it. Today I noticed that I've got little to no heat in the cabin. It has been taken for a 140 mile round trip on the motorway, so the engine has been up to temperature - coolant reading 90C as usual. (I have the 2.0 TDI 150PS)

Both heater matrix hoses in the engine feel warm to the touch, making me think heat is flowing into the heater matrix itself. I have tried the simple HVAC flap reset.
How warm were the hoses? They should be hot, certainly the inlet hose. It sounds like the matrix blocked, not fully but enough to cause issues. I’d be worried about the coolant drop, have a poke around for leaks
 

SuperV8

Active Member
May 30, 2019
743
315
Coolant expelled out your header tank is common symptom of blocked heater matrix - so is no/little heat in the cabin especially from the drivers side - passenger side will stay warmer.
The heater matrix is on the micro coolant circuit with the EGR cooler - when blocked there is not enough coolant flow through the hot EGR after a DPF regen so you get localised boiling and the coolant over pressurises and escapes safely out the cap.
Simple fix is a new heater matrix - loads of threads on here explaining how - but basically remove glove box and passenger side panel and heater matrix slide out towards passenger (LH) side. BEFORE fitting new heater matrix you should really have the coolant system fully flushed so your nice new heater matrix won't block up again.
 
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Reactions: Jay5959
Sep 12, 2019
9
0
Coolant expelled out your header tank is common symptom of blocked heater matrix - so is no/little heat in the cabin especially from the drivers side - passenger side will stay warmer.
The heater matrix is on the micro coolant circuit with the EGR cooler - when blocked there is not enough coolant flow through the hot EGR after a DPF regen so you get localised boiling and the coolant over pressurises and escapes safely out the cap.
Simple fix is a new heater matrix - loads of threads on here explaining how - but basically remove glove box and passenger side panel and heater matrix slide out towards passenger (LH) side. BEFORE fitting new heater matrix you should really have the coolant system fully flushed so your nice new heater matrix won't block up again.

Cheers for your response. Had a closer look today, and I think it is a blocked heater matrix. Feeling the heater hoses that directly connect to the heater matrix in the cabin, the inlet is hot and the outlet is warm/cold. Tempted to take it out and flush it through before putting in a new one.

Odd that it would get blocked up, the coolant was changed earlier this year.

Would you recommend flushing it out? If so, would you do it directly from the heater matrix, or from the hoses at the firewall of the engine bay?


Sent from my iPhone using Tapatalk
 

SuperV8

Active Member
May 30, 2019
743
315
Cheers for your response. Had a closer look today, and I think it is a blocked heater matrix. Feeling the heater hoses that directly connect to the heater matrix in the cabin, the inlet is hot and the outlet is warm/cold. Tempted to take it out and flush it through before putting in a new one.

Odd that it would get blocked up, the coolant was changed earlier this year.

Would you recommend flushing it out? If so, would you do it directly from the heater matrix, or from the hoses at the firewall of the engine bay?


Sent from my iPhone using Tapatalk
I flushed my matrix 4 times, each time would work for a few months - but then would block again, and I would get coolant low warning after a DPF regen.
I wouldn't bother with flushing the matrix - just get a new one. Only problem is Matrix prices are very seasonal - i.e. you pay twice the price in the winter than in the summer. Hope you can find one priced reasonably.
If you want to flush your matrix it's easy to take it out - I found garden hose adapters fit snugly in either end so I could flush a lot of mains pressure water through it. Collecting it in the bucket and keep going until minimal junk comes out. Like I said though - think of this as a temporary measure which may work for a few weeks/months.

Normally in 'simple' cars if your matrix blocks it doesn't really matter - just no heat - and you only notice that in the winter so prices go up! Our cars a blocked matrix is more important to fix.

There are VAG procedures for flushing your cooling system but they are rather involved - there are 4 circuits and lots of one way valves, so you basically clamp of 3 and then run water through the un-clamped circuit. You would take out the header tank and use the flow and return for connecting your hose to.

Whatever coolant flushing you do - do it with the old matrix in place. Then once flushed - fit the new one, so you're not flushing all the junk/detritus through your new matrix!
 
GAP Insurance - cover the difference for peace of mind