Hi there, wanted to ask for a bit of advice on how to open the coolant tank (see image for type) - is there any trick to it or special tool required? I've tried hands, rubber gloves, slip joint pliers but the thing won't move at all. Obviously, I've tried this with completely cold engine.

It should just unscrew by hand ,nothing special needed to undo ,yours must be well stuck for some reason.

Yes it is very stiff.  Extra weetabix for breakfast?😁

There is a lock detent. So you should feel it rotates slightly easy in that but requires force, anti clockwise to get past that. Usually two hands or two hands with non slip gloves is more than enough..  

Unless somebody has cross-threaded the cap, it will be tight. I usually recommend a light spray of silicon lubricant (and I mean light - wipe off excess) on the thread to ease the putting on and removal.

as above, should just unscrew by hand unless its been cross threaded.

There is a 'lip' which clicks the cap in place which you need to unscrew past at the beginning, but it should easily be achievable by hand.

A new genuine cap is around £20 in the UK 😞

Silicone spray on the cap and bottle, falls off like magic.

How many turns to remove it. I’m having the same problem. I can get the lid past the click then it gets very tight. 

11 hours ago, johnlwatts said:

How many turns to remove it. I’m having the same problem. I can get the lid past the click then it gets very tight. 

It will get very tight.  You cannot overtighten it.  There will be a satisfying click when its fully home.  Try taking it off, applying some silicon spray lightly to the threads of the cap and put it on again.

Having the same issue..had to use a wooden block and hammer to move it round. White sticky gundge all round threads, suspect silikat bag has burst. Wont tighten back fully either

AFAIK when the silicone bag goes, the coolant will turn a rusty brown colour (quick google shows the colour of the bag). You should be able to see the silica bag if the reservoir is marked 'Mit Silikat', unless it is a double walled tank.

Have you got a photo of the this gundge? Can you check the oil cap for anything similar?

White gunk sounds like something is allowing something to mix with the coolant... I'd be tempted to deal with the bag, flush the coolant and see how it goes.

Ah, you've just posted one. I was thinking more like this here.

That colour looks like the bag might have burst - it's a bit too orange and I'd hope on a 2020 car you don't have any rust yet. If you shine a light into the tank, is it still the same colour? Any visible bits inside?

I dont understand why bursted bag would change the coolant color. The coolant is in contact with the bag and the silica inside it all the time regardless.

Now that I take my attention away from some other forums and think about it, I'm not sure.

The change of coolant colour is usually due to either gunky old coolant, or some form of corrosion inside the system. That said, every 'coolant bag burst' post I've seen has the coolant being a bit of a dodgy colour.

Someone else will come along and offer further.

7 hours ago, albertz10 said:

Image looks like it's time for a new cap at least. Coolant seeping past the threads. Needs further investigation afterwards to see if system is over pressuring.

I cant see the bag anywhere..everything is working as it should, heaters etc.....changed the cap for now.

On 19/04/2025 at 13:12, OccyVRS said:

Ah, you've just posted one. I was thinking more like this here.

That colour looks like the bag might have burst - it's a bit too orange and I'd hope on a 2020 car you don't have any rust yet. If you shine a light into the tank, is it still the same colour? Any visible bits inside?

Dont have gundge like that, it was just round the threads if the cap and tank as if someone tried t oseal it up....no leaks and all seems good for now with new cap fitted.