M30 head rear cover plates

[Dash01]

What is the purpose of the two (firewall end) plates that bolt onto the rear of the M30 head? The irregularly shaped plate has bolt(s) that hold a wave washer and and O-ring, per parts drawing. What is the purpose of the O-ring, and is it critical to have its bolt be of a particular length?

[bill g]

I can answer parts of your question Dash01 -
I replaced my head gasket a couple of years ago and kept a few notes.
The covers are usually referred to as cam covers or cam end covers. All of the bolt holes are dead-end threaded holes except the outer one ie. near the rear passenger side (assuming US spec) head bolt. That bolt hole is drilled thru into an oil passage and therefore the bolt needs the O-ring to seal it.
ETK picture may be incorrect.
As far as I can remember the bolt is just the same as the others - I think the only thing critical about the length is that it would not want to be too long.

Bill G

[Dash01]

Thanks, Bill.

Suppose the O-ring were missing from that one bolt hole. What would that mean in terms of oil pressure? Any chance of the missing O-ring having anything to do with coolant getting into the oil?

Or, is the ETK simply drawn wrong?

[bill g]

Dash01 - I do not have a head off the car to look at but from memory I would say if the O-ring was missing I doubt it would make any difference to anything except you would probably have a bit of oil seeping out around the bolt head.
ETK looks wrong to me.
You could do a search for more info as the subject had been discussed before.

Bill G

[Dash01]

Dash01 - I do not have a head off the car to look at but from memory I would say if the O-ring was missing I doubt it would make any difference to anything except you would probably have a bit of oil seeping out around the bolt head.
ETK looks wrong to me.
You could do a search for more info as the subject had been discussed before.

Bill G

Thanks, Bill. I took the plates off, and found that the ETK is wrong--all bolts are dead ended.

Now, if I could just find out about the leak potential around the timing chain and water pump and whether the ETK is correct on that architecture , I'd know if that may be the source of coolant in my oil. (Head and headgasket are fine.)