Seat Leon FR MK3 Won’t Blow Hot Air

[ChrisMiskin]

Hey guys, never posted on one of these before but after the issue we are having, I have to ask as we are scratching our heads.

So I had a small coolant leak which turned out to be the coolant flange T piece pipe that leads onto the thermostat.
We didn’t have the pipe to change it there and then so I drove it home and ordered the pipe to fit the following day, we must have disturbed something as I overheated on the way home and dropped all the coolant, but turned car off instantly and fixed it there the following day.

Car was all good, no more leaking and holding pressure but we could not get it to blow how air for the life of us.

After a bit of investigating, we took of the inlet and outlet pipes of the heater matrix and noticed there wasn’t much flow going through the pipes, so we decided to replace the waterpump/thermostat with a new unit, which did not solve the issue.

Tonight we changed the heater matrix and thought we had it fixed, as after a while of idling and a few revs to get it up to temp, it started blowing red hot air inside, but on the drive home it was just lukewarm and wouldn’t get hot again.

We also noticed that one of the pipes from the heater matrix was boiling hot, and one was cold/barely warm.

Sorry for the long post but have tried to cover everything, we are so lost on what to look for now.

Any help would be greatly appreciated!

 

[Compo1]

Very difficult to bleed the mk3 so it could be an air lock.

If you have VCDS use it to bleed the high and low coolant circuits.

When you changed the matrix did you flush the coolant and replace the header tank if it had the silicat bag in.

If not you may have blocked the new matrix hence one pipe been cold.

 

[ChrisMiskin]

Yes we did flush the coolant and have replaced the new header tank too, have checked this one and there is no silica bag in.

I have not used VCDS to bleed it, I wasn’t sure if it was possible on this car, have only found tutorials for the diesels.

Do you by any chance know the steps I need to bleed on VCDS? I’ve not used it before.

Thank you for the reply!

 

[Compo1]

Yes we did flush the coolant and have replaced the new header tank too, have checked this one and there is no silica bag in.

I have not used VCDS to bleed it, I wasn’t sure if it was possible on this car, have only found tutorials for the diesels.

Do you by any chance know the steps I need to bleed on VCDS? I’ve not used it before.

Thank you for the reply!

Follow this mate

 

[nd-photo.nl]

Thank you for this @Compo1 !

 

[ChrisMiskin]

Follow this mate

I’m currently doing this now however I don’t have the option on the drop down for anything coolant related

 

[Compo1]

I’m currently doing this now however I don’t have the option on the drop down for anything coolant related

What model is your Leon ?

 

[ChrisMiskin]

What model is your Leon ?

Seat Leon FR 2015 1.8TSi MK3

 

[ChrisMiskin]

Car is now getting hot after about 20-30 minutes of driving, is stone cold for the first 15 minutes.
What could be the cause of this?

 

[Compo1]

Car is now getting hot after about 20-30 minutes of driving, is stone cold for the first 15 minutes.
What could be the cause of this?

How long does it take for your oil temp to hit 80 ish ignore water temp its not a reliable reading. With the oil temp 80 plus you should be getting hot air.

It looks as though you have cleared an airlock though so things are looking up.

Mine although a diesel is giving out warm air after about a mile hot after about 3 mile. Your petrol should be getting hotter a lot quicker.

Your car has a heater support pump to circulate coolant through the heater matrix before the main water pump opens when the engine's at full temp. At that point, the heater support pump shuts down and the main water pump takes over.

Easy way to test this undertray off get the car to temp so your getting hot air. Switch off the engine but turm the ignition on and then turn the heater to high.
Locate the heater support pump you should hear it if not be able to feel its working. VCDS does not always pick up a fault with these pumps as they can seem to be working but the impeller is loose on the shaft and does not spin so does not circulate coolant. If is humming you'll have to check the impeller is spinning visually which involves taking it off and you'll loose all the coolant when you do.

Might not be your problem but it is worth checking. It was certainly a problem for me.

 

[BillyCool]

Change of heater matrix can cause air locks in the system. It can take a while for the system to self-bleed. Try checking the coolant level every day when cold and top up if needed. You can bleed it but need special software and tools I think.

 

[SuperV8]

Car is now getting hot after about 20-30 minutes of driving, is stone cold for the first 15 minutes.
What could be the cause of this?

Check your heater control valve? 5Q0906457K

 

[SuperV8]

Check your heater control valve? 5Q0906457K

Or could be your Coolant regulator/pump 06L121111P - these have some rotary valves to direct coolant where required.

EA888:
The complete cooling water circuit – both internally inside the engine and on the vehicle side – was designed throughout to provide innovative thermomanagement (ITM), resulting in rapid heat-up of the engine and, as required, of the vehicle interior. The two main components of the hermomanagement system are the integrated exhaust gas cooling system as already described and the rotary slide module for implementing fully electronic coolant control. The complete cooling circuit additionally features switching valves to activate or block the flow through the heater and the gear oil heat exchanger. The central actuating element for the fully electronic coolant control and thermomanagement system is the plastic rotary slide module, housing two mechanically coupled rotary slides which regulate the cooling water flow. An electric motor drives rotary slide 1 by way of a heavily downspeeded worm gear. This is in turn connected via lantern gear toothing to rotary slide 2. Rotary slide 1 replaces the conventional wax thermostat, and is able to vary the cooling water temperature

During the warm-up phase, the cooling water flow into the engine is initially completely blocked by rotary slide 2. All external valves are closed, the water is standing throughout the engine. When heating is requested (in real-life customer operation), the standing water does not have to be completely used up. In this case there is an autonomous heating circuit with a dedicated auxiliary water pump via which the waste heat from the integrated exhaust manifold cylinder head is fed to the passenger compartment heater. The cooling water inlet into the engine block (rotary slide 2) remains closed, so maintaining the rapid heat-up function of the cylinder liners and reducing friction. The autonomous heating system means the customer’s comfort demands can be met and at the same time the optimum heatup strategy is implemented to minimise friction. Finally, as the engine temperature rises further, rotary slide 2 is slowly opened. This generates the minimum necessary cooling water volumetric flow to ensure adequate cooling of the components. The very rapid heat-up of the water further minimises friction in the warm-up phase.

Ultimately, as from a specified water temperature, the engine oil is additionally heated by targeted activation of the engine oil cooler by way of rotary slide 1.
Once the engine has been sufficiently warmed through, the switching valve to the gear oil cooler is finally opened so as also to warm up the gear oil with the surplus heat. The flow through the main water cooler entails heat loss to the surrounding environment and so, to deliver maximum fuel efficiency, occurs at the latest possible time. The integrated exhaust gas cooling system and the fully electronic coolant control thus provide the engine with a much shorter warm-up phase than its predecessor, and additionally speed up passenger compartment. Heating infinitely as required between 85 °C and 107 °C. Rotary slide 1 additionally regulates the cooling water return from the engine oil cooler very rapid heat-up of the water further minimises friction in the warm-up phase.

The innovative thermomanagement system permits optimum setting of the cooling water temperatures across the entire map so as to minimise friction and maximise thermodynamic efficiency. At low engine speeds and loads, the cooling water is adjusted to 107 °C in order to minimise engine friction. As the load and engine speed rise, the cooling water temperature is then lowered down to 85 °C,(bottom).
This provides the best possible compromise between reduced friction and optimum ignition efficiency (and minimum knocking), so ensuring optimum overall engine efficiency. The high adjustment speed of the rotary slide module and the high dynamism of coolant control achieved as a result enable the coolant temperature
to be lowered very rapidly for the jump to high loads. As a result, temperature overshoots in the components can be avoided. The innovative thermomanagement
system is rounded off by a special run-on function which is activated when the engine is switched off. The electric heating pump and a run-on setting of the rotary slide module then allow a targeted flow through the boil-sensitive cylinder head and turbocharger via the main water cooler, so enabling rapid discharge of the heat stored in those components. There is no flow through the engine block in the run-on position, so as not to cool the cylinder liners unnecessarily.
This function significantly reduced the run-on time, without generating excessive
heat loss. Overall, the ITM delivers a consumption advantage of 2.5 g CO2/km in the NEDC, with significant savings also in customer driving modes. It also provides high levels of comfort thanks to rapid heat-up of the passenger compartment.