Thermostat failure?

[Adjustingdrift]

Hi guys, I recently had a fault with my car ( 2014 leon cupra 280) which was a P261800 coolant bypass fault which decided to disappear one day but as I was driving to work I’ve noticed the EML light has came on and the coolant temp isn’t moving I’m guessing the thermostats gone? I’ve attached the codes

 

[TripleBob]

Have you checked to see if the silica bag is still in the coolant expansion tank? They’re notorious for splitting and dumping all their silicone into the coolant system - blocking it up

 

[Adjustingdrift]

Have you checked to see if the silica bag is still in the coolant expansion tank? They’re notorious for splitting and dumping all their silicone into the coolant system - blocking it up

I’ve just taken a look at it and I don’t see one in there is there any other signs that it’s released it all into the coolant system?

 

[TripleBob]

If you’ve not removed it, and the bag isn’t very obviously in the tank, it’s disintegrated and been sucked into the coolant system

 

[SuperV8]

If you’ve not removed it, and the bag isn’t very obviously in the tank, it’s disintegrated and been sucked into the coolant system

Not all tank's have the 'tea bag' type silicate pouch which some people remove - If the tank says 'mit silicate' and you can't see any bag, then it will be an internal repository.
The internal type and not removable so you would need to buy a new tank if you don't want silicate - though I'm not sure these internal types can leak like the teabag types!

 

[Adjustingdrift]

Not all tank's have the 'tea bag' type silicate pouch which some people remove - If the tank says 'mit silicate' and you can't see any bag, then it will be an internal repository.
The internal type and not removable so you would need to buy a new tank if you don't want silicate - though I'm not sure these internal types can leak like the teabag types!

Mine does say ‘mit silcate” and come to think of it I’ve never seen a bag in the tank even when I brought the car i don’t think it was in there if I remember

 

[TripleBob]

Not all tank's have the 'tea bag' type silicate pouch which some people remove - If the tank says 'mit silicate' and you can't see any bag, then it will be an internal repository.
The internal type and not removable so you would need to buy a new tank if you don't want silicate - though I'm not sure these internal types can leak like the teabag types!

True, but afaik all the 280 spec Cupras had the variant of tank with a bag in it

 

[nd-photo.nl]

Correct, might also be the previous owner removed it without mentioning it.

What happens with the coolant temps? Are they too high and it spits out coolant? Or the temp stays too low with a thermostat stuck in open position?

I created a video for removing the silica bag.

 

[Adjustingdrift]

Right so I’ve had the water pump and thermostat replaced as it wasn’t too bad for me being in the parts trade and all faults have cleared, coolant temps are showing again and running perfectly I’ve stripped the old pump and the pcb that controls the thermostat was soaked in coolant however interstingly it seems to be the original unit as the water pump was plastic too not metal so I’m surprised it’s lasted this long as the cars on 97k miles

 

[RUM4MO]

Correct, might also be the previous owner removed it without mentioning it.

What happens with the coolant temps? Are they too high and it spits out coolant? Or the temp stays too low with a thermostat stuck in open position?

I created a video for removing the silica bag.

The spec for the official VW Group G12evo claims that it is a long life engine coolant so does not need or has a recommended service life - only the aftermarket re-sellers of that BASF product, as usual, by default, are still advising a shortish service life.

In the past with crappy cam belts, we never needed to bother about this aspect of engine coolant as it got replaced along with the coolant pump while the cam belt was being replaced - but now with chains, long life cam belts and remote driven pumps, this "safeguard" has been removed. I certainly replaced the G12+/G12++ with G12evo at the 10 years old point in my S4, going to do the same with the G13 in my wife's 2015 VW Polo 1.2TSI, I have been checking the ph value/level in this car's coolant over its lifetime is proving to me that possibly VW Group should have been including "silicate dosing kits" on all cars that ended up being loaded with G13 at the factory - and not just the ones that were known to really need that "silicate dosing kit" to provide adequate engine protection.

 

[SuperV8]

Right so I’ve had the water pump and thermostat replaced as it wasn’t too bad for me being in the parts trade and all faults have cleared, coolant temps are showing again and running perfectly I’ve stripped the old pump and the pcb that controls the thermostat was soaked in coolant however interstingly it seems to be the original unit as the water pump was plastic too not metal so I’m surprised it’s lasted this long as the cars on 97k miles

Nice, glad it's fixed - water pumps/thermostats are common on the EA888.