Hi all,

Seeking any suggestions regarding a coolant issue.

There is a visually obvious buildup of brownish sludge in the coolant reservoir - sadly I don't have an image to hand, but I've attached the closest approximation I could find from google and I'll get a proper photo first thing tomorrow. The car currently has no heating, and a low coolant warning comes on intermittently - for example, tonight it came on once, and then went away after restarting. Engine seems to run well - no overheating (that I am aware of), smooth power delivery, no weird noises. The whole water pump repair was carried out recently (within approx. 20k kms) under different ownership - in fact it was done twice, the second time seemingly under warranty after the first one failed prematurely. EDIT: the reservoir tank fitted during that repair appears to lack the silicat bag.

It's quite late here so I may have forgotten to include some pertinent information... please let me know your thoughts, and thanks in advance!

Edited 5 July, 20255 Jul by m0thm4n
Add relevant info

Mentioning you are in Australia is good just for the nosy like me.

Then saying what it is, i checked so a vRS Wagon, is that a TSI rather than a TDI?

Hello, welcome to the forum.

Unless the Aussie model is significantly different, that does not look like a Mk3 Octavia expansion tank.

6 hours ago, Ootohere said:

Mentioning you are in Australia is good just for the nosy like me.

Then saying what it is, i checked so a vRS Wagon, is that a TSI rather than a TDI?

5 hours ago, Warrior193 said:

Hello, welcome to the forum.

Unless the Aussie model is significantly different, that does not look like a Mk3 Octavia expansion tank.

Ootohere, it is indeed a TSI.

Warrior, I've attached the image of my expansion tank here.

Reviewing the service history, 20k kms (almost 2 years) ago the water pump & thermostat, oil cooler & oil filter housing seal, and engine oil & filter were all replaced. The coolant was also flushed and replaced. The water pump & thermostat housing were replaced, and the coolant flushed, 3k km later, with the new header tank fitted.

I also checked under the oil filler cap - nothing untoward there. Given the state of the coolant, I'm hesitant to drive the car any more. My first thought was to flush the coolant again, but that doesnt seem so simple to do, based on other people's accounts and the service manuals.

The original EV image was very confusing.

That coolant does appear to be heavily contaminated, very likely caused by previous 'Mit Silicate' bag failure.

I see that this vehicle was not in your ownership when the original EV tank was replaced.

Lack of heating suggests that your heater matrix may be blocked - at the very least, your coolant system requires a through flush - as you note, refilling the system with correct coolant should be carried out using one or other of the recommended methods to avoid airlocks in the system.

It may possibly be the case that the heater matrix is beyond recovery - but worth trying flushing first.