Help! UFO found inside 1988 M6 engine

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Canadiane24
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Help! UFO found inside 1988 M6 engine

Post by Canadiane24 »

Long time reader, first time poster.

I'm the third owner of a 1988 M6. It is a Canadian car and appears to have been well maintained and is unmolested. It has 192,000kms (~120,000 miles for my US friends) I bought the car a year ago and have gradually gone through the suspension and brakes and am now onto the oily bits.

Currently I'm replacing the timing chain, crank sprocket and guides as a preventative measure. I removed the oil pan, front timing chain cover and chain tensioner. As I am removing the intake cam sprocket I hear the"tinkle" of falling metal. I take the cam sprocket out and find this shiny silver object resting between the timing chain and the lower guide, the one which engages the tensioner. I had not yet removed the exhaust cam gear or the idler gear. The disc obviously fell from above and came to rest in that position as there isn't a mark on the disc or the guide.

The timing gear looks entirely normal. The guides and sprockets have surprisingly little wear given the mileage. There are no unusual marks on any of the moving parts that I can see. At the first oil change after buying the car I cut open the oil filter. There was no metal. Of course these cars don't have a gauge but the oil light works and goes out as soon as I start the car. I've driven it 5,000 kms so far and the engine has not burned any oil or made any funny noises.

The disc looks to be a sealing plug. Other than wiping the oil off, it is exactly as shown in the pictures. It is 22mm and made of aluminum. It looks to have been staked in place as there are four areas around it's circumference where the lip is pressed flat. There is no sealant residue stuck to the plug. The plug is not damaged or deformed, as surely it would be if it came in contact with the cam gears or chain while operating. I've looked everywhere inside the engine and on realOEM.com. I can't find anywhere inside the engine that this plug should go. There is a plug on the upper passenger side of the cam chain cover but it is steel, a couple millimeters smaller and still in place.

It must have been resting up near the top of the head as I heard it fall as I was removing the intake cam gear. A couple months back I checked the valve adjustment and replaced the valve cover gasket. In checking each valve I would have spotted this plug had it been in plain view.

It's possible it was inadvertently dropped into the engine through the oil filler opening at some point in the last 30 years.The filler opening is near the area where this plug may have rested before it fell. Seems unlikely but I'm grasping here.

Any ideas? I'm stumped.
Plug found in engine 1.JPG
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Plug found in engine 2.JPG
Plug found in engine 2.JPG (344.07 KiB) Viewed 8961 times
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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zinnocoupe
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Re: Help! UFO found inside 1988 M6 engine

Post by zinnocoupe »

Welcome to the forum, nice to see another Vancouver e24 owner here. That is definitely a odd hunk of metal to find rolling around in your engine. I'm afraid I can't help you as I don't have any S38 experience. I sure someone else here with knowledge of that engine can help unless it was something dropped into the engine at some point. I'm just curious about the car, was this the Zinno M6 that had been sitting in an underground parking garage for some time just outside of downtown? I saw one on CL that sold in a flash about a year ago. Please post some pics of the car and what you are doing to it. I hope someone who recognizes the "item" comes forward soon.
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Stoffie
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Re: Help! UFO found inside 1988 M6 engine

Post by Stoffie »

To my untrained eye, that looks a lot like a freeze plug from the block. :shock:
The M88/3 was all about power, no cats. At idle the raw fuel from the exhaust will make your eyes water like an old V-8 powered muscle car's exhaust did.
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zinnocoupe
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Re: Help! UFO found inside 1988 M6 engine

Post by zinnocoupe »

Realoem lists 36mm and 45mm freeze plugs for the s38 block. It could still be a freeze plug from something.
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
1977 530i Partially restored and running now!
1987 635csi 60K KM Garage Queen
Canadiane24
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Re: Help! UFO found inside 1988 M6 engine

Post by Canadiane24 »

I thought it might be a freeze plug as well but it's too small and made of aluminum. My limited experience with freeze plugs is they are steel or brass. I don't think it is an oil gallery plug either. They are threaded so as not to come loose, as this plug clearly has.

Zinnocoupe, I don't think this is the car you referred to. This one was owned for the last 15-odd years by an elderly man in Surrey. I bought it from a friend of the family when the owner moved into an assisted living facility. I heard about the car by chance and don't think it was advertised for sale.
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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zinnocoupe
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Re: Help! UFO found inside 1988 M6 engine

Post by zinnocoupe »

OK I agree, I think all the freeze plugs for m30s and s38s are thinner steel that have been zinc coated (by looking at pics online etc)

It does sound like a different car, good luck with it all. Post some pics
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
1977 530i Partially restored and running now!
1987 635csi 60K KM Garage Queen
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raykoke
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Re: Help! UFO found inside 1988 M6 engine

Post by raykoke »

Yeah... seems nothing on realoem resembles that...

http://www.realoem.com/bmw/enUS/partgrp ... g=11&sg=05

Cheers,

Ray
'85 ///M635
baders
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Re: Help! UFO found inside 1988 M6 engine

Post by baders »

Fallen out of the mechanics top pocket is my guess :D
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Canadiane24
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Re: Help! UFO found inside 1988 M6 engine

Post by Canadiane24 »

Baders, your's is the most plausible so far. :D

Anyone? Plan to reassemble the engine this weekend. Would suck to have it buttoned up and learn later where this plug went.
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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raykoke
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Re: Help! UFO found inside 1988 M6 engine

Post by raykoke »

99.9% of the parts for the motor are itemized on realoem.

See if you can find it there.
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zinnocoupe
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Re: Help! UFO found inside 1988 M6 engine

Post by zinnocoupe »

OK so I was just looking at my getrag 265/6 transmission to check and see about wether or not it has the speedo cable drive I need to install it in my new e12 ( it doesn't and I know that but just wanted to look at the plug than covers where the cable drive would be.) The plug thats in there looks very similar to your plug thing. It looks to be aluminum and close to the same size. Its about 23mm. Its pretty close to what you have.
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ImageIMG_1161 by Dave Grayson, on Flickr
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
1977 530i Partially restored and running now!
1987 635csi 60K KM Garage Queen
Canadiane24
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Location: Vancouver

Re: Help! UFO found inside 1988 M6 engine

Post by Canadiane24 »

Zinnocoupe, thanks for the excellent pics and thinking of my quandary. The one on your 265/6 looks to be slightly larger.

I thought maybe the plug originated from under the oil breather baffle plate bolted to the underside of the valve cover. Nope. After re and re at least now I know what's under the plate. Nothing.

The crank sprocket didn't arrive so I did not reassemble this weekend. Next weekend I guess, without the UFO.
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
Canadiane24
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Joined: Mon Apr 24, 2017 4:10 am
Location: Vancouver

Re: Help! UFO found inside 1988 M6 engine

Post by Canadiane24 »

Update:
Reinstalled the new chain, crank sprocket, tensioner and guides and buttoned it together. Runs good, no funny noises and no oil leaks. Fall back to DEFCON 1.

Guess the UFO must have fallen into the engine at some prior service. Probably when valve adjustment was done by PO. Lucky it didn't move and get ground up and cause a whole bunch of (expensive) pain.
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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hornhospital Online
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Re: Help! UFO found inside 1988 M6 engine

Post by hornhospital »

Glad you got it sorted and it's running well! =D>

I hope you mean DEFCON 5. DEFCON 1 is the highest alert status. :shock:
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Canadiane24
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Re: Help! UFO found inside 1988 M6 engine

Post by Canadiane24 »

Oops! Yup, definitely not on high alert. =P~
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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