Cactusjack

Could be blown head gasket, leak in egr cooler as above or charge air cooler, or at worst a cracked cylinder head... If there's definitely no leaks visible on the outside of the engine, or no coolant/oil mixing then it's getting into the exhaust gas from one of the coolers, or a gasket fault from water jacket to exhaust, or a crack inside a cylinder to the exhaust manifold... Buy a sniff check kit from Amazon/eBay and let it run at temperature for a while, a small leak will show eventually if you have one! I had a hairline crack in number 2 cylinder on my VRS TDI and would need to refill the expansion tank every few hundred miles, it never overheated but would blow the exhaust gas temperature sensor in the manifold overy so often, I lived with it for almost a year!

https://procarmanuals.com/pdf-online-skoda-octavia-iii-2013-octavia-iii-2014-1-6-66-77-81-2-0-105-110-135-kw-tdi-cr/ page 185 onwards.

You get a special cap for the reservoir with quick release fitting on the top. The vacuum fill kits come with various caps for most cars.

You don't have to vacuum fill, however it makes it so much easier! Without it, you'll be chasing air out the system for a while, but might get lucky... All depends if you don't mind spending the time doing that! There are circuit bleed options on VCDS however that can help move any trapped air along.

Have a look through this https://procarmanuals.com/pdf-online-skoda-octavia-iii-2013-octavia-iii-2014-1-6-66-77-81-2-0-105-110-135-kw-tdi-cr/

There's no way of knowing what the new ECU has been coded with without the info from the seller, and without plugging it in and checking via ODIS unfortunately. I had my car taken a VAG specialist who got a new ECU from Germany via TPS and freshly coded it scratch to my car, no problems since... I shorted mine by fumbling the rachet when changing the battery and arcing it of the ECU case, ended up with a fully dead car! Dealers and other specialists said I was stuck as changing an ECU couldn't be done... BS!

Give CJ Mechanical in Notts a look up, he's down by Lady Bay Bridge. Great specialist indy, very knowledgeable and trustworthy, he's sorted some difficult issues for me that puzzled many dealers and "specialists".

I changed my ECU at the start of the year, absolute nightmare to get right... Went through 3 2nd hand ECU's and couldn't get them coded correctly via ODIS, best chance for 2nd hand one needs to be an exact match for your car with same engine code and gearbox code, they're locked once they're set... In the end I bit the bullet and got a brand new blank ECU for £1300 to start fresh 😞

Stock works fine when it works... If that makes sense? Receiving calls and voice replies for messages are good, however if I'm making a call then it can take a while for the mic to connect even after the call is answered, so some people hang up on me... More bluetooth related than mic though that part I'm guessing!

I replaced my cracked cylinder head about 2 years ago, absolute pig of a job on the floor in my garage! Just steer clear of a dealer as they seem to lack the knowledge for correct diagnosis and you'll end up out of pocket replacing stuff that won't correct your issue... A VAG specialist will see you right more often than not.

Balance shafts are present on both the CUPA and CUNA 135kw EA288 engines. Crankshaft and balance shafts will be replaceable with the right equipment and knowledge, manual says not however it's likely related to them being installed once and the designers thinking there's no need to replace... Probably easier to get whole 2nd hand crankcase though!

Yeah it's repairable, would guess at £1k+ by dealer, a little less from an indy... Head gasket change requires the removal of a lot of components! Have to factor in cambelt and waterpump, aux belt, gasket set for the head/exhaust manifold/charge cooler/cam cover sealant, new head bolts, fluids and other service items if about due etc... Fully drain the oil and coolant and have a look for contamination with the other then go from there, you can refill with clean fluids to get you to a garage, or tackle yourself if you're that way inclined!

Smells like BS to me... These ECU's are a funny beast and some coding cannot be changed but as others have said, the key and car were working previously so they have been communicating correctly. At the end of the day the car was driven in, in working order and they have done something to render it unusable, so I'd be pursuing them to rectify it. It's up to them to prove fault, not yours, and driving it in weighs in your favour! The key and immobiliser codes are in the instrument cluster if I'm not mistaken? Surely a new key fob can be coded by an VAG specialist who has the use of ODIS? I would get a second opinion from them.

MIB Columbus screen is a bit bigger.

Yes they do, is it a different display that shows on yours? There's an option in the settings to switch between OEM and aftermarket display. Or does it not switch at all? As for the maps, I'm not too sure as I've not noticed it...