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Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI  
Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - 6speed

Hi,

Can anyone help with this one?

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.

Thanks for any help you may be able to offer

Cheers

Tags: technical issues cam belts unexplained noises maintenance and servicing

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - Collos25

Can you check and see if the new cam belt is a notch out there should be some timing marks on the pullys.If its set correctly then there is a far deeper problem and probably requires the head off.

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - Peter.N.

Is this definitly a mechanical knock or could it be an injector?

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - Peter.N.

Is this definitly a mechanical knock or could it be an injector?

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!

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - madf

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

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - 6speed

Thanks for your replys,

I have taken the head off, number 1 piston is in trouble!!

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - robbo2

I have an astra doing the same thing, what was wrong with number 1 piston,

Thanks Rob

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - 6speed

Hi,

Looks like it has picked up on pison and scored the bore and ruined piston.

All back together now running nice

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - robbo2

Hi,

Have got a van thats doing exactly the same as yours took the head off today pistons look ok but bores are slightly scored on 2 and 3

Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - cal38spl
h
Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - cal38spl
Hi
Vauxhall Astra G Diesel - Knocking Astra 1.7 CDTI - 1litregolfeater

So what was the outcome of all this?

I have to look after a 1.7 DTI, which sounds very healthy to diesel enthusiasts, but painful to my ears.

Sorry to be a pedant, but how do you tell if a diesel engine has a knock? As it's all bam clattery bang anyway?

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