Check Engine Light (CEL) is lit & steady and running rough. on 2000 Porsche 911

I had my water expansion tank replaced, two weeks later the CEL lit and had the Porsche Dealership service the car, their code findings were cylinder 1-3-5 not working. Causes could be cooling leak into them.

The car started and ran fine until engine temp. reached 180 degree then it started to idle rough plus the CEL lit & stay on while driving. The car do not burn or smoke from pipes at start-up or while idling.

Any ideas what could causing this problem, I appreciate any info of a possible solution.


Asked by for the 2000 Porsche 911
Cylinders 1 and 3 are on the driver's side of the engine. number 5 cylinder is middle cylinder right side of engine. if the engine has a blown head gasket it would be that both head gaskets are blown which would be odd. Get a second opinion preferably from a repair shop that specialize or have extensive Porsche knowledge. He a simple chemical test called a block test done, it looks for the presence of carbon monoxide in the cooling system which would only be present if the head gaskets were blown. Don't drive the car if this is the case as more serious/expensive damage will occur.
Thanks for your answer and suggest as well, The Porsche Service Tech. had thought the same thing with cylinder 5 error code, He did say it could be a head gasket to worst case is a crack block, also said perhaps an Ignition Coil need replacement could cause the CEL to display too.