Seat Leon 2.0 TDI coolant loss

[Mangoad]

Hi, I have a 64 plate Leon FR 2.0 TDI (184). My coolant seems to disappear to which several mechanics have had a look, however recently I have also had a low engine oil light appear.

They’ve pressure tested the expansion tank to which it’s held pressure.

They have done the fluid dye test which stayed the same colour.

There are no visible leaks of coolant.

Timing belt and water pump was done 10K miles ago.

I have no signs of milky oil, however I am aware that my heater matrix is partially blocked, as this was diagnosed by the previous owner and there is a difference in vents left(hotter) to right(colder). The cars radiator fan does kick in quite often.

Could this be a head gasket or just a heater matrix. Any advice or similar experiences would be appreciated.

 

[BillyCool]

Hi, I have a 64 plate Leon FR 2.0 TDI (184). My coolant seems to disappear to which several mechanics have had a look, however recently I have also had a low engine oil light appear.

They’ve pressure tested the expansion tank to which it’s held pressure.

They have done the fluid dye test which stayed the same colour.

There are no visible leaks of coolant.

Timing belt and water pump was done 10K miles ago.

I have no signs of milky oil, however I am aware that my heater matrix is partially blocked, as this was diagnosed by the previous owner and there is a difference in vents left(hotter) to right(colder). The cars radiator fan does kick in quite often.

Could this be a head gasket or just a heater matrix. Any advice or similar experiences would be appreciated.

During a DPF regen a blocked heater matrix can't keep the coolant cool enough so it effectively boils it and vents via the over-pressure vent on/around the expansion tank lid/cap. Technically, not a leak but a forced exit. As the system is pressurised, you usually only get a low coolant light the next day when the car is cold and system is not under pressure. This always creates the impression that you have a leak.

You can get an OBD reader like Carista and the VAG DPF app to monitor when your car does a regen. Once the regen is complete have a look at your header tank and you'll probably see evidence of some coolant loss.

I'd certainly replace the matrix and flush out/replace as much coolant as you can. See if that helps. A lot of people also replace the header tank to one without a silicate bag in it.

In terms of cost, you'll get lots of prices from £1200 for SEAT to do it (their tech docs say remove the dash), an Indie for about £300 to £400 or the DIY ghetto fix of a £80 matrix and about 3 hours of your time.

 

[Mangoad]

Expansion tanks coolant has gone brown since then, so I’m guessing it’s the silica bag that’s been blocking it and it’s now slowly rising up.

Will get the heater matrix replaced and a coolant flush and will update on this thread.

Thanks.