Hello!

Coolant is slowly disappearing.

Engine oil is also consumed (about 0.5 liter per 3000 km).

There is a sweet coolant smell and some steam from the exhaust.

There is oily residue on the edge of the coolant expansion tank.

There are no fault codes, no visible smoke, no oil leaks and no coolant leaks.

The following parts have already been replaced:

EGR cooler

valve cover

coolant expansion tank

expansion tank cap

oil filter housing

timing belt, water pump and all drive belts

There is no mayonnaise under the oil filler cap.

On cold start, the engine makes a slight rattling noise for about 10–20 seconds, then it runs normally.

I am trying to understand if this could still be a head gasket or cylinder head problem.

Thank you!

Skoda Octavia 3, 2014(2015 model), 2.0TDI (CKFC)

Pressure test and a sniff test next IMO.

IMO? Co2 test? Anyway, the CO2 test came back positive, meaning the liquid changed from blue to green.

1 hour ago, Pikaa said:

IMO? Co2 test? Anyway, the CO2 test came back positive, meaning the liquid changed from blue to green.

Then coolant is escaping into the cylinder block. Either cylinder head gasket or EGR cooler has failed.

23 minutes ago, varaderoguy said:

Then coolant is escaping into the cylinder block. Either cylinder head gasket or EGR cooler has failed.

Thank you very much! What is the easiest way to find out this without taking the engine apart? In other words, should I make sure that the car really has a cylinder head? As I wrote, the EGR cooler was replaced and the water consumption was still the same. The water consumption was both before and after the replacement. The EGR cooler was replaced because we disconnected the cooler and then, interestingly, it didn't consume water, we replaced it afterwards, but the water consumption continued.

1 hour ago, Pikaa said:

IMO? Co2 test? Anyway, the CO2 test came back positive, meaning the liquid changed from blue to green.

IMO = In My Opinion. Sorry, I didn't realise English was not your first language

3 minutes ago, Lee01 said:

IMO = In My Opinion. Sorry, I didn't realise English was not your first language

I finally figured it out, but thanks for your answer! 🙏

19 hours ago, Pikaa said:

Thank you very much! What is the easiest way to find out this without taking the engine apart? In other words, should I make sure that the car really has a cylinder head? As I wrote, the EGR cooler was replaced and the water consumption was still the same. The water consumption was both before and after the replacement. The EGR cooler was replaced because we disconnected the cooler and then, interestingly, it didn't consume water, we replaced it afterwards, but the water consumption continued.

The easiest way of determining whether its the cylinder head gasket that has failed is with a Borescope. Take out the injectors, looks at the mixture chamber and also the cylinder head. If its REALLY shiny and not full of carbon (most TDI's get fairly mucky inside the combustion camber and cylinders) then that is the first indication. Second indication is pressurisation. Pressurise the cooling system (I wish I could remember what the PSI figure should be - others might be able to help me here) and look inside the cylinder - if you see coolant weeping from top to bottom, then you know the gasket has failed. Third way - drain the oil - if it is a horrible [known as Forbidden Smoo] - a milky creamy substance, then that is also a good indicator that you have coolant in the oil.

probably new egr cooler leaks too. if you bypassed egr cooler and then have no coolant drop, it aint head gasket. test old egr cooler for leaking.

this not look like head or head gasket to me.

On 12/01/2026 at 11:47, varaderoguy said:

The easiest way of determining whether its the cylinder head gasket that has failed is with a Borescope. Take out the injectors, looks at the mixture chamber and also the cylinder head. If its REALLY shiny and not full of carbon (most TDI's get fairly mucky inside the combustion camber and cylinders) then that is the first indication. Second indication is pressurisation. Pressurise the cooling system (I wish I could remember what the PSI figure should be - others might be able to help me here) and look inside the cylinder - if you see coolant weeping from top to bottom, then you know the gasket has failed. Third way - drain the oil - if it is a horrible [known as Forbidden Smoo] - a milky creamy substance, then that is also a good indicator that you have coolant in the oil.

Unfortunately, I can't find a mechanic here who can do all this. So the engine disassembly remains.

Thank you very much for your answers!

On 12/01/2026 at 01:17, Pikaa said:

we disconnected the cooler and then, interestingly, it didn't consume water

Id say that disproves it.

But did you bleed the system properly after egr removed? If not you may have subsequently cooked the head/gasket

2 hours ago, Pikaa said:

Unfortunately, I can't find a mechanic here who can do all this.

You canny find a mechanic who can use a Borescope camera, but you can find somebody to dismantle your engine. That sounds very odd.

You could try a leak down test on each cylinder. It might help pinpoint where its gone. It should tell if the head gasket is failing but dont think it can check EGR cooler. If the EGR cooler is new then I doubt its the problem.

Alasdair

3 hours ago, BlueWagon said:

Azt mondanám, hogy ez cáfolja.

De légtelenítetted rendesen a rendszert az EGR eltávolítása után? Ha nem, akkor lehet, hogy utána beégetted a hengerfejet/tömítést.

According to the mechanic, yes, he bled the air! Can you tell me how such a process works, just so I know.

I have another question about coolants. I know the manufacturer says G13, but many people recommend G12. What is the truth?

2 hours ago, varaderoguy said:

Nem találhatsz olyan szerelőt, aki tud boroszkópot használni, de igen, aki szétszereli a motorodat. Ez nagyon furcsán hangzik.

You're right, there must be a mechanic who can look into this...But the oil consumption is definitely coming from inside the engine, am I right?

Edited 15 January15 Jan by Pikaa

4 hours ago, Pikaa said:

I know the manufacturer says G13, but many people recommend G12

Arh - slightly complicated. Your car needs G12Evo. This is not G12 or G13. What happened was that G13 was introduced around 2017, but VAG realised it was not environmentally friendly, so they created a modified G12 with additional cooling properties for more modern engines. The result is G12evo and is valid for most VAG cars from 2016 onwards (although any vehicle except a 2015 TDI150/180 combination) which need G13.

Edited 15 January15 Jan by varaderoguy

7 minutes ago, varaderoguy said:

Arh - slightly complicated. Your car needs G12Evo. This is not G12 or G13. What happened was that G13 was introduced around 2017, but VAG realised it was not environmentally friendly, so they created a modified G12 with additional cooling properties for more modern engines. The result is G12evo and is valid for most VAG cars from 2016 onwards (although any vehicle except a 2015 TDI150/180 combination).

Thanks. Could this have caused a bigger problem for the car if it had been filled with something other than G12 (not g12 evo!)?

Edited 15 January15 Jan by Pikaa

I have decided to have the cylinder head removed, and the mechanic said it would be easier to do it with the engine taken out.

If the cylinder head is removed, is it worth going deeper while the engine is already out, or is it unnecessary to further disassemble the engine if it is clear that the issue is with the head gasket?

If the head is removed and there are no signs of head gasket failure then it could be a cracked block but very unusual unless its been totally cooked or perhaps frozen. You say the oil filter housing was replaced. Did that include oil cooler?

Alasdair

23 minutes ago, Alasdair1 said:

Ha a hengerfejet leszerelték, és nem látszanak a hengerfejtömítés meghibásodásának jelei, akkor lehet, hogy megrepedt a blokk, de ez nagyon ritka, hacsak nem sült meg teljesen, vagy esetleg megfagyott. Azt mondtad, hogy az olajszűrő házát is kicserélték. Az olajhűtővel is ez történt?

Alasdair

But if, for example, it is clearly visible at the head gasket that there is a failure, then there is no point in disassembling the engine any further, right? The oil filter housing had both coolant and oil leaking before, but that was about 1.5 years ago, so it did not happen recently and it was not caused by freezing.

If the engine is running well apart from the coolant/oil problem and if its just the head gasket then I would replace and not go any further unless I had to. If you are removing head then get it checked for flatness before refitting in case its warped. I would check the oil cooler again first. Its 1.5 years old and I find even OEM parts dont last as long so could be failing.

Hope you get it sorted

Alasdair

7 minutes ago, Alasdair1 said:

If the engine is running well apart from the coolant/oil problem and if its just the head gasket then I would replace and not go any further unless I had to. If you are removing head then get it checked for flatness before refitting in case its warped. I would check the oil cooler again first. Its 1.5 years old and I find even OEM parts dont last as long so could be failing.

Hope you get it sorted

Alasdair

The machining (skimming) is definitely required! What should we check on the oil cooler, what should we pay attention to?

Before skimming head check its possible. If it is warped some modern engines cant be skimmed by much due to fine tolerances (sons landrover td5 being one) and may also need a thicker head gasket. As for the oil cooler I think the simplest way is to remove and pressurise with air and submerge in water and look for leaks/bubbles. You could also check EGR cooler if the engine is removed the same way.

Alasdair

And it does this when the engine is cold if I take the cap off...
Video