Anyone in the world ever heard of this issue?
At the rear driverís side of the cylinder head there is a flange to which the heater core hose gets clamped. The flange is bolted to the aluminum head with two bolts. If you unbolt that flange, remove it, and peer into the hole that it covered, you will see what appears to be a sleeve-like piece of metal that was perhaps pressed into the head. If you look at figure 28 of Wayne Dempseyís Pelican Technical Article BMW Head Gasket Replacement, which I have included here as the first attachment, you can see a bit of this sleeve. This photo is, as far as I know, the only place in the world where a glimpse of this part can be seen. None of the manuals has a diagram that shows it. Parts dealers havenít even heard of it. I should mention that this is the cylinder head of a six cylinder M52 engine (from a 1996 328i). Iím not sure what engine is pictured in the Dempsey article.
So why does this mysterious piece of metal concern me? Because the one on my cylinder head is so corroded and deformed that it is not likely serving the purpose it was intended to serve, whatever that purpose might be.
The machinist who reconditioned the head brought this issue to my attention. He wasnít sure what to do about it. His initial suggestion was to try to remove the disintegrating part. I donít want to do anything before I can make an informed decision, but as I have already indicated, I havenít been able to find any such information.
In the second attachment you will see a picture I took of my cylinder head from roughly the same angle as the one in Dempseyís article. You can see from this photo how badly corroded this piece is. And it gets worse further into the head where jagged fragments of metal seem to curl toward the centerline of the hole so that you cannot put your finger in but an inch or so.
The third attachment is my attempt to show you what it looks like further into the head. As already mentioned, itís a bit of a train wreck in there.
I bought this car from relatives of the deceased former owner, so I know very little about its history. I removed the head to replace the head gasket which I had reason to believe was not properly sealing. Along the way it would have been nice to find something that might have been the root cause of the gasket failure, so that it could be corrected and thus give me confidence that the new gasket wonít fail for the same reason. But I havenít found that smoking gun, and so I would like to right all the wrongs I find with the hope that one of them may have been the root cause. If this mystery part served to redirect the flow of coolant and in doing so effect a more even temperature distribution in the head, perhaps its erosion was the root cause for the head gasket leakage?
Here are my options ordered from what would be the most satisfying to what would be the least satisfying.
1) I could find the actual part somewhere, somehow, and replace the disintegrating one with it. I havenít found such a source, but perhaps someone out there knows of one. Is there someone at BMW I should get in touch with?
2) I could have a replacement part fabricated. This would depend on me obtaining a sufficient description of what the part should look like. Is it just a hollow cylinder, open at both ends, or are there openings in the cylinder walls? If so, where are the openings and how big are they? Is the inner end capped? Does the tube taper at all? Maybe someone who had a similar head sitting around could look at the piece in question, and (providing it is not as disintegrated as mine) could give me a description of what its geometry should be.
3) Someone who knows would tell me what the purpose of the inserted sleeve-like piece is, so that I could then guess at what the part should look like and fabricate one.
4) I could remove the remains of the piece that is there, not replace it, and hope for the best. Assuming BMW had a reason for inserting that piece where they did, this option is not very satisfying to me.
5) I could do nothing and put the engine back together as is. In addition to the reservation mentioned in the last option, this option leaves the possibility that more pieces will break off the disintegrating part and cause trouble elsewhere in the coolant circuit.
If anyone could shed any light at all on this issue, I would be very appreciative. Thanks for reading this lengthy post.