Hi all,

I've got a 2011 Skoda Octavia 1.6 MPI (Petrol) and the coolant level keeps dropping. The oil cap is milky and I'm worried the head gasket might be gone.

See engine photo here

I assume it's a 1.6 BSE engine, but can't find a good diagram of the coolant system to work off.

Reading around online, I understand there could be an issue with the oil cooler, but I'm not sure where this is located and what the part number is to order a replacement.

Can anyone help point me in the right direction?

Many thanks

Edited 3 November, 20253 Nov by SomethingRandom
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Good morning, welcome to the forum.

Rather than just replacing suspected parts, the first thing you need to do is test the coolant for combustion products and have a compression test done.

Your engine code can be found on your V5 document as the first 3 or 4 characters of the engine number.

I've had to replace two parts of the cooling system due to failures on my BKD:

The header tank had perished on one side where the sunshine was getting in under the bonnet and UV attacked the plastic. Replacement cost about £15 from ECP.

The other was a bigger job, it was the radiator that was leaking!

1 hour ago, SomethingRandom said:

Hi all,

I've got a 2011 Skoda Octavia 1.6 MPI (Petrol) and the coolant level keeps dropping. The oil cap is milky and I'm worried the head gasket might be gone.

See engine photo here

I assume it's a 1.6 BSE engine, but can't find a good diagram of the coolant system to work off.

Reading around online, I understand there could be an issue with the oil cooler, but I'm not sure where this is located and what the part number is to order a replacement.

Can anyone help point me in the right direction?

Many thanks

Thanks for the tip, don't know why I didn't think to check the V5!

I've ordered a test kit and will check the coolant before doing anything else.

46 minutes ago, chrisund123 said:

I've had to replace two parts of the cooling system due to failures on my BKD:

The header tank had perished on one side where the sunshine was getting in under the bonnet and UV attacked the plastic. Replacement cost about £15 from ECP.

The other was a bigger job, it was the radiator that was leaking!

The header tank doesn't look great, but there are no signs of it leaking. I'll take another look this evening just in case, would be great if that was the issue!

If there is emulsified oil on filler cap it could be the headgasket thats failing/failed and coolant is getting into engine. It can also happen if you do short journeys and the engine doesnt get upto temp. The fact that the coolant is dropping means its got to be going somewhere. Does the car produce any white smoke when running or can you see any crystal deposits around rad,coolant pipes or under car. Check the front passenger carpet as well in case its the heater matrix thats leaking. The oil cooler I think is near the oil filter and looks like this.

5 hours ago, SomethingRandom said:

The header tank doesn't look great, but there are no signs of it leaking. I'll take another look this evening just in case, would be great if that was the issue!

A leaking header tank won't however be causing your emulsified oil issue.

Does the engine have regular oil changes?

13 hours ago, Warrior193 said:

Good morning, welcome to the forum.

Rather than just replacing suspected parts, the first thing you need to do is test the coolant for combustion products and have a compression test done.

Your engine code can be found on your V5 document as the first 3 or 4 characters of the engine number.

I've run a CO2 test this evening and it appears to be negative (unless I've done something wrong - the liquid was moving around but not exactly bubbling through). No noticeable colour change after 10 mins running with a warm engine.

6 hours ago, Warrior193 said:

A leaking header tank won't however be causing your emulsified oil issue.

Does the engine have regular oil changes?

Yes, oil changes have been regular and the oil looks fine on the dipstick.

8 hours ago, Alasdair1 said:

If there is emulsified oil on filler cap it could be the headgasket thats failing/failed and coolant is getting into engine. It can also happen if you do short journeys and the engine doesnt get upto temp. The fact that the coolant is dropping means its got to be going somewhere. Does the car produce any white smoke when running or can you see any crystal deposits around rad,coolant pipes or under car. Check the front passenger carpet as well in case its the heater matrix thats leaking. The oil cooler I think is near the oil filter and looks like this.

I'm now hoping this is the issue? I just can't find where it is (and forgot to check the V5 for the engine code).

Front carpets appear to be okay, and I don't see any crystals anywhere. It's true most journeys are short, so maybe that's part of the issue.

Edited 3 November, 20253 Nov by SomethingRandom
Add photo link

20 hours ago, SomethingRandom said:

the coolant level keeps dropping

How much?

Say 1L per week or from full mark to empty in 2 months? Need a measure of the volume of coolant leaking.

7 hours ago, SomethingRandom said:

the liquid was moving around but not exactly bubbling through

That bubbler would rely on a perfect seal at the top.

Did it have that?

Oil cooler may be leaking slightly.

Again, we need to know how much coolant is being lost

Does your tank have a tube from cap for expansion. In the past a failed cap on one of my cars was causing coolant to be forced out as the coolant wasnt getting properly pressurised. I put a plastic bottle on end of expansion drain tube to check and found coolant in it after a short journey. Replaced cap and all good. Clean up the emulsified oil from cap and take for a decent run to see if it comes back. If its very slight it could be down to short journeys and condensation.

Alasdair

On 04/11/2025 at 06:55, BlueWagon said:

How much?

Say 1L per week or from full mark to empty in 2 months? Need a measure of the volume of coolant leaking.

That bubbler would rely on a perfect seal at the top.

Did it have that?

Oil cooler may be leaking slightly.

Again, we need to know how much coolant is being lost

It's not actually my car, so I think the best course of action will be to monitor the coolant level for a few weeks and report back.

The seal around the bung was good, the material was fairly flexible so I feel it was ok. Might retest it again at some point just in case (maybe with higher revs).

On 04/11/2025 at 08:31, Alasdair1 said:

Does your tank have a tube from cap for expansion. In the past a failed cap on one of my cars was causing coolant to be forced out as the coolant wasnt getting properly pressurised. I put a plastic bottle on end of expansion drain tube to check and found coolant in it after a short journey. Replaced cap and all good. Clean up the emulsified oil from cap and take for a decent run to see if it comes back. If its very slight it could be down to short journeys and condensation.

Alasdair

Thanks, I'll check this. Will clean up the cap and take it for a drive this evening.