any one here who knows what the issue is. i took out the engine and change valves and camshaft couple of month ago also change timing belt and water pump diverted water from egr cause this car is mapped. also cleaned everything from the dpf so it is empty. seems to be leaking air in to the system or is it a possibility that the new water pump is failing after 2000km. the car goes in overheat but it is enough to switch it on of and then it goes down to normal level. i parked the car yesterday and this morning i opened the coolant house and it had high pressure. 

26 minutes ago, kiddi79 said:

i opened the coolant house and it had high pressure

quote + title make me wonder about head gasket failure. I suggest doing a chemical sniffer test on the coolant.

Hey. Been searching the answer for a time now. Mine is 1.6 tdi not maped and its consuming coolant when I drive 130+ km/h. The message for coolant level always come up the other day when the engine is cool. My first tought it was the EGR cooler since there were some spots that suggested as coolant leak (and previously i had error code P040100 ''insufficient  EGR flow''). So i swaped the Egr cooler and the egr itself. The problem still exist. My conclusion is that the coolant expansion tank is beeing presurized and the coolant overflows and spills from the vent on side of expansion tank and drips behind the wheelarch (weird is that the leak never appears on the ground- must be leaking while I'm driving it).  The car its not overheating, the heating matrix I guess its not blocked since the heating works fine, the silica bag was previously taken out from the cooling expansion tank, water pump was changed 60kkm before, due to fail.

I'll try to do a pressure test to see if maybe the cap itself is not venting and that creates overpressure in the expansion tank. Its absurd that this problem exists on 100+ octavias, Seat has same problems... and no one knows the issue. Even more absurd sounds that all cars would suffer head problems. Well mine its making me ''head problems''. Anyway if you get to the point of problem please let know.

On 17/04/2022 at 15:07, kiddi79 said:

any one here who knows what the issue is. i took out the engine and change valves and camshaft couple of month ago also change timing belt and water pump diverted water from egr cause this car is mapped. also cleaned everything from the dpf so it is empty. seems to be leaking air in to the system or is it a possibility that the new water pump is failing after 2000km. the car goes in overheat but it is enough to switch it on of and then it goes down to normal level. i parked the car yesterday and this morning i opened the coolant house and it had high pressure. 

Does the thermostat work.

Kiddi79 Did you find the solution yet? I found many threds (on some seat forum) about cooling water beeing blow out of expansion tank because the heating matrix being clogged. In my case my heating is working fine. Do you have hot air blowing from all vents?

I would try to flush mine heatinx matrix, a lot people reporting some debris clogging it up.

Just finished flushing the heat exchanger in cabin. It had some debris inside looking like chunks of rust and some other really fine particles. I flushed with tap water from both sides to make sure all debris went out. I even tried to blow inside and i think the air flow is good enough. For better result I would need to flush all system.

Then I put all back together topped up the coolant and started engine with heat on until it reached the temp then topped up to between min and max. Tho I'm pretty sure it will burst the coolant out off expansion after next dpf regeneration 😵.

Here are some pics of debris i found inside.

18 minutes ago, doctavia said:

I flushed with tap water from both sides to make sure all debris went out

 

You'll never get all debris out, because within heater matrices the incoming and outgoing large-bore connections split up into many smaller bore pipes which are all in parallel. If any of these are partially or fully blocked with debris, your flushing fluid will preferentially go through others instead.

 

Here are some pics of a Vauxhall one I cut up many years ago:

 

Edited 3 May, 20224 yr by Pete_Ex-Wino

On 03/05/2022 at 11:23, Pete_Ex-Wino said:

 

You'll never get all debris out, because within heater matrices the incoming and outgoing large-bore connections split up into many smaller bore pipes which are all in parallel. 

Good to know. 

for my car i belive it was a mistake from when we the hedd was put back on it wasnt clued on as it is suppose be 

So it was the problem in the head gasket? 

Yeah I think so I haven’t put it together yet though 

https://www.briskoda.net/forums/topic/461262-mk3-coolant-nightmare/page/2/#comments have a look at the end of this thread for my experience.

Cactusjack your result its the one im hoping not to be.. Since my last update its been 3 weeks in the mean time I was checking the water regularly and didnt have the burst since then. I can tell that water level fluctuates up and down and Im stil not quite sure if its ok when car its been driven and then cooled down after night I still have that small "hisss" from expansion bottle when i open it. Can anyone check that on his car? thanks