Coolant leaks NG9-3 B207

[Philippe]

Hello from France !

First let me thank you for letting me in this forum. In few words, here is my problem. I own a SAAB 9.3 MY2009 2.0t biopower with only 37.000 km. This is a first hand car. When reaching 27.000 I started to experience coolant loss especially in city driving. What has been done so far : circuit hold pressure, even overnight, there is no coolant in oil, seen on the dipstik, and I also sent a sample to a lab. I found one leak at heater core (O'rings). Still the leak was there. Changed thermostat, all hoses (do88 ), radiator (do88 ), radiator cap and reservoir. Recently I bought a CO2 leak detector and found that only at high temperature, say starting at 95C the fluid turns from deep blue to green, but not yellow indicating CO2 in coolant but not that much. There is no apparent oil in coolant, but I did a full flush and some oil was in. I put AC delco pellets in the coolant tank, and after few days at high temp the co2 detector remains blue (good news). It has sealed something. My saab dealer suggest having the cylinder head removed and tested and the head gasket changed. At the same time, Orio wrote a PI recognizing casting defects in short blocks MY2003 to model MY2006, then they say that used reinforced blocks, reducing the likelihood for porosity to occur, but it stayed at a lower occurence rate, MY2007 to MY2001. Ah, also forgetting, no overheating so far. Maximum temp I had is 106c in harsch conditions : mountains driving during a hot summer.
So, if it is porosity of the block it should have begun from the very beginning ? Or is it just appearing now ? is there a way to test for porosity ? Saab dealer says he.has never seen a broken head gasket on these engines, but saw a lot of cars losing coolant at various rates. Car runs fine. So quite lost.
I agree removing the cylinder heads, but if they found nothing they will question the short block. Any ideas/comments are welcome. Losses depend on the driving conditions, eg on the highway I loose nothing.

Best

Philippe

[Alexander B]

Welcome here, Philippe.
It is good to read your "engineer's approach". I agree to most of the things, including not hearing much about head gasket problems on these engines. One suggestion though; have you checked the water pump? I can imagine some scenarios where the seal has a seepageat lower rpms, but sealing well at higher rpms at the highway.
A pragmatic approach if you find nothing, is to keep driving, and keep monitoring. Good luck!

[turbo4ever]

Bonjour!

Had similar issues (but no mix with engine oil) on a MY2008 B284L with 150 000 km. Turned out to be a partly defect water pump that was leaking (no visible coolant leakage when parked) and normal coolant temperature all the time (despite the leak). I doubt that the cylinder head or gasked needs changing after only 37 000 km. It is very unlikely on a B207.

[Alexander B]

OP has not been here since mid June, and he did not comment on my post then, so I doubt we will hear back from him.