Hi all,
Sorry for the long message but I found this forum really helpful and want to help anyone on this situation similar to mine.
My car started suffering with this problem 6 months ago when one day the warning appeared. No coolant at all in tank so I though it was definitely a leak, topped it up and the coolant stayed. I didn't know what to think but the mechanic checked for leaks and changed water pump. A couple hundred miles later coolant again gone. Mechanic advised to keep driving until the problem become more consistent.
Blowout kept happening, naturally I thought head gasket but no creamy residue on cap or other signs etc. Got it serviced as it was due and second mechanic checked for leaks - didn`t find anything. Blowout kept happening and saw some videos regarding egr cooler leaks.
I noticed that sometimes when I opened the coolant cap, some coolant would come back up into the tank. I thought maybe faulty cap so replaced that, but no luck. Took it to third mechanic who checked for leaks and suggested thermostat. At this point I researched and was sure that coolant was being burnt via egr cooler, mechanic suggested first change thermostat - again after some driving the blowout happened again. At this point I had lost hope and thought the egr cooler was linked to dpf cycle, that is when I found this forum.
Coming into the winter I noticed that I had luke warm air, condensation very quickly building up inside cabin, fan speed would reduce when turned heating to hot, but temp on dash was never above 90. I then noticed that after 250-350 miles the blowout would happen which I have read is about the dpf cycle. Looking at the success of changing heater matrix and my disappointment in my mechanics, I decided to change it myself. Ordered a nissens matrix and when I cut open my old one the coolant had become solid and blocked half of the matrix so I don't think it is worth trying to clean old matrix.
I can report after 500 miles that it has worked!! I am a newbie so took me six hours, relatively simple but hard to reach screws slow you down.
I was worried when a few days later the coolant level had dropped by about 100 ml but after filling up it has been fine since, must have been air locked in the system after matrix change.
Its interesting how this seems to be a common issue but not many mechnics I spoke to knew about this. Will keep you updated but this chat has helped me immensely.