Last saturday I finally solved that mistery. I checked belts,tensioners ,water pump and cam shafts. Everything looked OK, but engine still had same diesel sound. you should checked if camshafts are OK, because a lot of Opel engines has problems with camshafts.
After I checked everything I found out that noise is coming from intake manifold. Opel call it twinport. So I dissmantled it.
First you must remove engine computer, fuel and water hoses, cables…
Then you will see 2 types of screws. One are for splitting manifold, other attach twinport to engine. You unscrew all of them and split twinport in half. Do it gently don’t use iron hammer. And you don’t want to damage intake gasket.
This is how lower part of twinport looks like:
And upper part:
In lower and upper part of twinport you will see 2 screws, if they didn’t fall out already 🙂 This attacheted part is causing tapping noise ( diesel noise 🙂 ).
I dissmantle it and clean it. The I put some high temperature sealent and screw it on manifold.
Put it together and SOLVED. Petrol engine sounds again like petrol engine 🙂
Another mistery is, how engine can bee so dirty?! Its has just 100 000 km. Oil changes are regular, nothing is leaking! See right side of pic.
