Nono, its not performance related.. It has to be caused by frozen coolant :S It was a 2.0 V70R junkyard block, what I fully rebuilt. Rebored to 83mm, shimmed, ported headt, etc... I have never seen this before so I wasn't prepared to check the block side for cracks :S I didn't notice that 1.5cm crack on the block, also when I torqued the head there was a loud snap sound. Later it tuned out that was the moment when the harline crack expanded. After the hard work on that engine and 20 hours of installation on that day, everything ready to go... it was a pain to see coolant coming out on the bottom. Tried to weld it wihout success.