Rocker area Knocking

[andyh01]

Hi,
It's a 5.0 Litre Pre Serp. On my way home from work I was suddenly aware of a knocking noise on tick over. I have since listeded more carefully and it definitely seems to be from the rocker area rather than manifold.

I removed the Oil Filler cap and to my surprise it was rather dry in there. I know it shouldn't be swimming in oil, but I can touch the visible tappets without getting oil on my fingers ???

Obviously the oil level is fine, and only lives on Mobil 1. Oil Pressure also shows normal. Last had a full Oil change about 4K Miles ago, but obviously has been through a good few pints of Mobil 1 during this period. Is it possible that there is an oil blockage, or even a problem with the oil pump ? Or am I barking up the wrong tree.

Thanks,

Andy H.

[johno]

Andy,

It really could be a long list of things ..

1 - Exhaust manifold gasket, they really can be very similar
2 - It could be a tappet/lifter cam issue
3 - Could be a rocker issue, lost pad
4 - Could be a loose inlet trumpet knocking

The sounds around the engine bay really do travel to funny places....

I would be very careful checking for exhaust leaks first, then I would have an expert listen to the noise and try to determine the issue, they will have more experience.

I would really doubt there is an oil blockage, given the regular oil changes and unless something foreign has ended up in the oil system to block enough of the oil pathways to stop it feeding the top end. If it has stopped, then you will need to have the top end checked out anyway in case of any damage. I have heard of excessive use of silicone sealant on valley gaskets in particular to stop them leaking then coming away from there original position and causing issues around the engine, but very rare and would depend on whether the car has had recent engine work.

You can run the engine with the oil cap off to see whether there is oil being fed into the rocker box, but do it when it is cold and make sure you wear safety glasses and do not allow it to splash out of the filler neck ... Not something I'd really recommend, but if you really want to know then it would would one way. I am presuming therefore that there is no splash plate.

In addition you are feeling the top of the rocker arm. The oil is pressure fed through the rocked gear, so it may not appear to be as oily as you imagine ... Good luck.

[andyh01]

Thanks Johno. I will check again this evening with an open mind, and post my findings. Regarding the oil blockage theory, I have already removed the filler cap whilst the engine is ticking over, and there is absolutely no spray, and no visible lubrication (accepting that I cannot see under rocker). I will compare this to the other bank.

Andy.