[Corsa C 2000-2006] Engine knocking but seems slightly louder when warmed up

[dpash1974]

Hi everyone,

I have a knocking sound that seems to be coming from under the rocker cover. The noise seems to get more noticeable when the engine has warmed up to normal running temp.

All the fluid levels are fine and I have done an oil and oil filter change but it has made no difference. Could it be a problem with the camshaft as when I took the oil filler cap off the end of the camshaft you can see seemed to have some wear on it (chips and pitting) ?

[Taurus]

Which engine?

If the cam lobes are worn then chances are the oil feed is restricted so the hydraulic followers may also be gummed up. Depends on the age / mileage of the car how much work you want to do.

Use a stethoscope or a big screwdriver (handle your ear - tip to various parts of the engine)(and obviously be careful not to get anything caught in moving parts) to make sure exactly where the noise is coming from.

If it's not worth doing anything major then you could try one of the snake oil formulas for clearing noissy hydraulic lifters - Wynns do one - I've known people use them and find they work a bit. They basically contain a chemical which breaks down the gum in the followers. I was talking to a chemical engineer a while back who went into what is in the stuff - but the details are lost in my ageing brain cells.

Don't be tempted to use an oil flush, they can be too aggressive and loosen debris inside the engine which causes more problems. You're better off doing some frequent oil changes - try using oil for diesel engines, it has more detergent in it.

If you find the knocking is lower down the engine then none of the above will make any difference. Oil pressure is created by the fine tolerances in the engine, not by the pump. If there is wear in the bearings then oil flows too freely through them causing the oil pressure to drop, and of course oil flows more freely when hot which is why oil pressure drops as the engine gets hot. If the noise is at the top end and due to the lifters then restricted oil flow through the lifters will get less pressure as the engine warms up - clearing the restriction will therefore help.

[dpash1974]

Hi Taurus,

I have the 1.2 twinport and it is a 2005 model. I have had done an oil and oil filter change and put some wynns hydraulic lifter formula in but it still seems to be making the same noise.

It definitely sounds like it is coming from under the rocker cover so I am wondering if I have a worn camshaft ?

[Taurus]

They use hydraulic followers so that takes up wear. The camshaft would need to be very worn before they make much noise. Usually it's the lifters that are the cause but the only way to be sure is to take the cover off nd inspect.

[zuluman]

Was it not this engine (or slightly earlier year??) which suffered form loosening of the camshaft bolts.

Check and retorque correctly

[dpash1974]

Hi Zuluman,

I am not sure but I do recall reading about something along those lines but the year escapes me. I will take a look.

[Taurus]

They usually snap the camshaft without warning if that happens - reports of any particular year affected proved to be false as any of them can suffer from it. If you read the reports it claims to be a fairly common problem, yet in reality a very small proportion of them seemed to actually suffer the problem given the huge number produced. Worth checking though - just use a torque wrench set to 8Nm to make sure they are all tight. You can do it whilst you've got the cover off to check the state of the lobes.

Check also the oil breathers whilst you've got the cover off, you see a lot of them with totally clogged breather pipes.

[dpash1974]

Well had the rocker cover off and not a happy bunny. Looks like whoever fitted the new timing chain didn't remove the metal bar that locks the cam and the end of the cam is broken, the rocker was rattling around like a marble in a bucket and the valve has been damaged.

[zuluman]

Well had the rocker cover off and not a happy bunny. Looks like whoever fitted the new timing chain didn't remove the metal bar that locks the cam and the end of the cam is broken, the rocker was rattling around like a marble in a bucket and the valve has been damaged.

FFS