SteveOctavia19tdi

Thanks T07. From what I read the egr opens after regen adding a surge of heat through the egr cooler which causes the boiling /increase in pressure if the flow is restricted or air locked or gasses have leaked into the circuit. I got it all back together, thoroughly bled all circuits and went for a spirited drive. All seemed ok, so after half an hour I did a forced regen whilst driving. This lasted about 10 mins and after another 5 mins or so driving to cool down I checked the coolant. There had been some loss at the expansion tank but not loads. Another sniff test showed combustion gasses again. So I think as you suggest, the charge cooler is the next thing to look at. I shall first try a pressure test on it in situ as it's easier to get to than the egr cooler.

Thanks Pete. I've been having another go at it and having removed more stuff I have actually managed to get the erg cooler off from above, I didn't need access from underneath in the end. I've done the pressurise underwater test and there are no leaks that I can see so it may well be ok after all. However, I shall replace it with a new one just to be sure, and I don't fancy doing the job again any time soon!

I'm struggling with my brother's 2.0Tdi Octavia, 2014 CKFC and would appreciate some help. He was getting fairly regular low coolant warnings and was having to top up. I'd had similar with an A3 and in the absence of any leaks, and with clear evidence the coolant had blown out of the expansion tank I changed the heater matrix but that didin't make any difference. I have also bled the cooling system thouroughly several times using vcds which hasn't helped. The symptoms seem to be: No sign of any leaks anywhere apart form obvious high pressure forcing out coolant at the expansion tank. The level remains fairly steady then will suddenly drop after a longer drive. On these drives there have been occasions when the in-car heating suddenly seems to get hotter. No loss of performance and it never overheats. No white smoke from the exhaust. Heater matrix changed and coolant replaced. Heated works fine, both sides. Bled several times using VCDS. Sniff test at the expansion tank showed combustion gasses present. I'm thinking when the regeneration occurs it creates too much pressure, either due to partial blockage or more likely exhaust gasses leaking into the cooling system, leading to pressure release and coolant loss at the expansion tank. From what I have read a failed ecg cooler is a likley cause, so I thought I would have a go at changing this. However having started the job it is looking even harder than I thought! I'm beginning to think I won't be able to remove the egr cooler - especially as it is 4x4 giving even less access. I wondered if I could bypass the cooling by joining the two egr hoses together then see if the symptoms persist. If I did this would it be ok to drive for a while with the egr still functioning but without its cooling? Or can anyone suggest a better course of action or other things I should be doing first?

Having thought more about it I've remembered that I didn't change or flush the coolant because I had done the water pump and cam belt the month before so the coolant had been replaced then. Having looked on youtube there are videos for changing the heater matrix on the octavia, looks pretty much the same, just less stuff to remove to get to it.

The matrix was something under £100 (Nissens). I did it myself based mainly on this youtube vid having watched a few others for extra info. It took a while but wasn't too difficult. I clamped the heater pipes in the engine compartment so didn't lose too much coolant. I didn't do anything with the header tank nor flush the system as it looked pretty clean. I did have a slight leak on the lower joint for a few weeks after - the solution was to remove the clamp (I had refitted the Audi one) and used the nissens clamp having bent the tabs in a bit to ensure it was really tight,

Thanks. So if each is fused I'm guessing the red is maybe permanent live and the yellow switched live, and under the red tape they are not joined to anything. Maybe the black wire coming from above is an earth. Not sure about the blue wire though. I will investigate further!

My 2004 Octavia has finally reached the end - too many things needed for the mot, and too many little jobs keep needing to be done. The remapped engine is still pulls well at 273K though! So I have just bought a 2015 187k 2.0tdi to replace it. All seems good. However, I noticed some modification to the wiring around the OBD port area. Does anyone know what this might be for? I've not disturbed it so it's not clear where each wire is coming from/going to. The blue wire looks to come from the main harness towards the port but it is then not connected to anything. Likewise the yellow and the red wires look to come from the main harness towards the port? but then each have one of the 'big plastic connectors' (I don't know what these are) and then both appear to be joined to a single black wire that disappears up into the dash somewhere. Most of the service history is main dealer, but I wouldn't say this looks to have been finished very professionally. The port seems to function fine with VCDS. Finally, is there a piece of trim missing here? I didn't remove any.

I had the same symptoms on my son's 2014 2.0Tdi A3, I think the same engine. It turned out to be the heater matrix starting to get blocked. A tell tell sign apparently is that the drivers side stops blowing hot air. I changed the matrix and it has been fine since. From research it appears that when a regeneration occurs the pressure gets too high due to the partially blocked heater matrix and the extra pressure forces coolant out of the expansion tank and it pools around that area.