I have an astra van 1.7 CDTI with the Z17dtl engine, it has a knocking sound from the top end, it sounds like a very loud tappet, ie same frequency/speed. I have had the top off today and all looks to be ok, its obvious that someone has had it apart recently and they have also fitted a new cambelt?
I have checked valve clearance and they are fine, checked timing, pinned the cam and pump refitted the cam belt and its still the same, thought it could have been a diesel knock?
As i cant see any obvious problem i have started to wonder if i have inherited somebodys problem, as i said the cam cover looked like it had recently been off, plus new cambelt. I have heard that the cam lobes can be turned on the cam shaft after a cambelt failure, I am starting to think that this may have had a snapped belt at some point and hit valve, then repaired and sold on with the knock.
The engine runs fine just has this loud tappet knock, If the Cam Lobes have turned slightly on the shaft would this cause the knocking sound? I have examined the shafts and i am a little suspect of a couple of the lobes on the exhaust side but its very hard to measure accurately.
Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI -
Steve the Scrute
Got this with a car at work. Sounds exactly as described. Instinct from listening to the engine this afternoon is that the exhaust manifold is either blowing or cracked where it butts up to the head. Will keep you posted once I`ve had it to bits!
Agree with Steve. First check exhaust manifold for leaks when hot... this can be easier said than done as it will be hot and I have no idea of accessibility... I used to use a bare hand... highly dangerous and not recommended...
A piece of card dipped in water would be safer - look for drying out areas