Engine oil from camshaft cover tapped hole

[triple e]

When looking for the source of a metallic knocking in the vicinity of the drive belts on my Rover 75 Diesel CDT 2001 I removed the large top engine cover. This is the one held in place with the 3 bolts with 1 being screwed into the top of the black part of the end cover over the camshaft - it's on the car offside over the 2 drive belts.
I left these 3 bolts out and started the engine looking for the cause of this metallic knocking.
Immediately oil started to flow out of the tapped hole over the camshaft and of course I stopped the engine.
My query is : should this tapped hole be permitting oil to come out as the only seal with the bolt in position is the bolt itself which is not good engineering practise. I had noticed before there is a small amount of oil around the area of this cover but had not located its source - now I know.
I think the noise is from the belts/pulleys/adjusters or bearings of driven units but need to get closer into the area with offside wheel arch cover off to see (I hope).
Any advice will be much appreciated

[Rev Jules]

When looking for the source of a metallic knocking in the vicinity of the drive belts on my Rover 75 Diesel CDT 2001 I removed the large top engine cover. This is the one held in place with the 3 bolts with 1 being screwed into the top of the black part of the end cover over the camshaft - it's on the car offside over the 2 drive belts.
I left these 3 bolts out and started the engine looking for the cause of this metallic knocking.
Immediately oil started to flow out of the tapped hole over the camshaft and of course I stopped the engine.
My query is : should this tapped hole be permitting oil to come out as the only seal with the bolt in position is the bolt itself which is not good engineering practise. I had noticed before there is a small amount of oil around the area of this cover but had not located its source - now I know.
I think the noise is from the belts/pulleys/adjusters or bearings of driven units but need to get closer into the area with offside wheel arch cover off to see (I hope).
Any advice will be much appreciated

I had this problem and found out it should be a shorter bolt than the other two, obviously someone has screwed in a longer bolt and gone through the bottom of the cover.

Rev Jules

[EastPete]

I think that someone may have used longer 8mm bolts than the originals for attaching the engine cover - this can then damage the cam cover when tightened down. I am not sure what the cure is.

Knocking from the belt/pulley area on a CDT is most likely due to worn/damaged crank pulley, but other pulleys on the belt run (water pump etc.) can also wear and cause vibration/knocking.

Pete

[Rick-sta]

Your oil leak coming from the engine cover bolt hole is a common issue. My dads 75 has the same problem. If you look at the 3 bolts for the engine cover, you should have 1 bolt which is shorter than the other 2. The shorter bolt is for the thread the oil is coming form. Unfortunately at some point someone would have put the longer bolt into in there, which is too long and pierces through the bottom of the thread, causing oil to come out.

Put the bolt back in with a thick paper washer and the leak stops :)

[Heddy]

All as above. The bolts are M6 x 20mm long. Most have gone through causing a leak. It isn't normally a problem, the 'blind' tapped hole is a brass insert. If the large top cover (3 bolts) has the correct grommets fitted these will seal around the hole as the cover is fastened.

[triple e]

Many thanks for the rapid responses from Rev Jules, East Pete & Rick-Sta.
All logical and with hindsight now (and with your information) all too obvious. If all 3 bolts had been the same shorter length originally there would not have been this problem for any of us.
Now down to resolving the original belt knocking problem.
I have to find out how to thank guys like you all on this great, friendly and informative forum. When I do I will be thanking you all.

[triple e]

Thanks Heddy - that's interesting re the 'blind tapped hole' being a brass insert. Might it be possible to remove the black camshaft cover and press back in to relocate the brass insert correctly to effectively seal the hole?

[triple e]

I've looked at the bolt/steel spacer/grommet configuration holding the top engine cover in place and would be sure it doesn't provide a fully effective oil seal. Have I missed something? Have any others found this problem and have any found a solution?
Any advice appreciated - I plan to do the work this weekend, weather permitting,

[Heddy]

Thanks Heddy - that's interesting re the 'blind tapped hole' being a brass insert. Might it be possible to remove the black camshaft cover and press back in to relocate the brass insert correctly to effectively seal the hole?
The brass insert is the tapped hole, a plug if you like. The hole is of limited depth until a longer bolt is used and pushes the bottom out of it. The cover really does prevent oil escaping (in the majority of cases anyway) You might want to try a rubber washer (tap washer) underneath the cover, with a tight 6mm bore.