Happy New Year all.
The AAN in my UrS4 seems to have what I can only guess is a head gasket leak, however something very strange I cannot get my head around and need a bit of help answering:
Starting up = no smoke / water from the pipes at all. good as gold. (bit of blue, but she's an old girl so don't care)
First 15-20 minutes or so at idle = no smoke whatsoever. perfect.
Thermostat opens, reaches operating temp or close = and BANG, it smokes whiteish smoke / condensation and drips lots of water as soon as the stat opens up - or at least I am assuming the stat opens up. Literally like a switch, i have watched it.
Have driven for 20 minutes keeping a close eye on all temperature readings, from the CC unit and temp gauge. She does not overheat at-all, running well and maintains perfect operating temps but smoke does not go away while at operating temp. Definitely not weather related, it was doing it back in the height of summer.
A long shot, but does the turbo have seals for the coolant lines that could be leaking? I can't think why it would only smoke when the thermostat opens up?
Thanks
The AAN in my UrS4 seems to have what I can only guess is a head gasket leak, however something very strange I cannot get my head around and need a bit of help answering:
Starting up = no smoke / water from the pipes at all. good as gold. (bit of blue, but she's an old girl so don't care)
First 15-20 minutes or so at idle = no smoke whatsoever. perfect.
Thermostat opens, reaches operating temp or close = and BANG, it smokes whiteish smoke / condensation and drips lots of water as soon as the stat opens up - or at least I am assuming the stat opens up. Literally like a switch, i have watched it.
Have driven for 20 minutes keeping a close eye on all temperature readings, from the CC unit and temp gauge. She does not overheat at-all, running well and maintains perfect operating temps but smoke does not go away while at operating temp. Definitely not weather related, it was doing it back in the height of summer.
A long shot, but does the turbo have seals for the coolant lines that could be leaking? I can't think why it would only smoke when the thermostat opens up?
Thanks
The only way to prove me wrong is to do a compression/leak down test. 
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