Combustion gasses in coolant

[denniselbows]

Just replaced the head gasket on my car and I'm still getting co2 in the coolant . I'm wondering if its possible or if anyone has ever had a crack in the turbo that has caused the exhaust gasses to get in the coolant . The car runs fine and at cruising speed down the motor way you wouldn't know there's a problem . But when in traffic and slow driving in the 30 s the temp starts to cheap up . No signs of water in the oil and the thing that makes me wonder about it be ing the turbo is I found the after run pump had seized up so no after engine off cooling to the turbo. So has anyone heard of this or had such a fault before .

[quattro-nick]

why did you replaced the head gasket on the first place?
did you carry out an internal lektest of the cilinderhead and is the bottom flattened?
i dont think your turbo is the problem

[denniselbows]

The head gasket was replaced as a result of the engine getting really hot pore running. A compression test was carried out which found number 4 cylinder was down compared to the others only 10 psi but still down . A combustion leak test found combustion gasses in the coolant system . The head was replaced with my Spare which was pressure tested for cracks and skimmed, my straight edge was checked against the skimmed head to see if there was any high or low spots on it . Then used to check the level ness of the block which I couldn't get a 3 thou feeler gauge in anywhere so was taken to be good . A victor reinz head gasket was used so I have no reson to suspect the head , gasket or block deck . I couldn't see anything to suspect a crack in the bores . The bores look good to be honest no scores or heavy wear . You could still see the cross hatching in some of them .

[Monkeymagic]

Have you done another block test to indicate the further signs of combustion gas?

[quattro-nick]

did you place a metal gasket and have you use new headstuds?

[denniselbows]

Yes I have carried out another combustion leak test this morning and there is defiantly combustion gasses getting in to the coolant . A new multi layer metal head gasket was used ( victor reinz ) and a new set of head bolts . When torquing the head down I used the method that came with the head gasket 30 nm then 60 nm then 90 degrees then 90 degrees the 3b manual stated slightly different 40 nm 60 nm then 180 degrees but 90 then 90 would be ok . At the end of the day there is only 3 or 4 ways combustion gasses can get in to the coolant. Head gasket, done cracked head tested ok , or cracked/ porous block, maybe most likely or possibly turbo coolant line which is doubtfull but possible .

[Mikes2]

The other possibility is that the head is not being clamped down properly.

Had that on my own car. Damaged head bolt threads in the block. When torquing the head bolts, some of them were torquing out early.

Not saying that's your problem but worth checking. Was there any water getting in the oil. It goes a light brown coffee colour.

[220bhp]

Did you clean out the bolt holes before you replaced the head. If not a build up of fluid muck, dirt etc, can stop the bolts from reaching full depth and not clamping the head down completely, even when reaching the correct torque.

[denniselbows]

Yes the bolt holes in the block where cleaned out. I used one of the old head bolts and cut a line the threads and made it in to a sort of tap to clean out the threads and also used some paper towel made it in to a small sausage and fead it in every hole so soak out any oil or water in the holes . A friend has offered a loan of a turbo to try although I do think it is very unlikely it is the cause, but it is something I need to rule out. Looks like I'm going to have the head off again and recheck every thing again . Great fun