UFO in sump!

Imagine my joy and surprise when this bolt emerged from the sump of my 996 attached to the magnetic drain plug last week! It appears to be a M6 allen headed bolt with approx. 25mm of thread, well chewed and with some evidence of stripped thread from whatever it was previously attached to I'm wondering how worried I should be and where it might have come from. Car runs fine with no adverse noises or such like. If it had come loose in my ownership, I think I'd have heard it rattle through the engine so I'm assuming it has been there for some time It is a 2002 3.6 C4 Tip with 117k miles. The engine has not been apart in the 7000 miles and 2 years that I've had it. It came to me freshly serviced, I changed the oil and installed the magnetic plug this time last year. Previous owner had it for 2 years and 28,000 miles with no apparent engine work. I've got some receipts going back to 2015 which indicates AOS and oil filler pipe where replaced in March that year. Could that bolt have anything to do with the work to change the oil filler pipe? Grateful for any thoughts

Hopefully Hartec Baz or DeMort will be along shortly to say where its from.

Looks like a bolt from the camshaft area, they are similar for the tappet chest, a big worry is, it looks like it took some heavy hits on its was down to the sump? It could have been there for years but now you have fitted the mag sump plug it's raised its ugly head.

Someone dropped a coil pack bolt when changing plugs? :dont know:

Dropped it where? If it went down the plug hole it wouldn't make it to the sump. I don't recognise the unthreaded end on the bolt. MC

No. 11 here is my best guess .. https://www.deroure.com/diagrams.asp?MAK=3&MDL=25&TBL=2523&SMA=&SMO=0&ST=&SC=0 All you can do is drop the sump pan and have a look .

Me too, its not a bolt I recognise from the M96 engine with the waisted end but the engine has obviously been apart at some point in its life so someone may have used a generic bolt instead of buying the correct ones?

It wouldn't have far to go if it was already in the sump and that bolt has taken a few blows from moving engine parts, there is nothing in the sump that could do that? Plus that is showing as a hex head bolt? I was thinking number 18 here? https://www.deroure.com/diagrams.asp?TBL=2518&MAK=3&MDL=25&SMA=0&SMO=0&ST=&SC=0

After reading your thoughts on this then i'm of the opinion it's possibly no.47 .. its a head bolt under the chain guide .. if lose it will run the gauntlet of the timing chain before entering the sump .. If it was a cam cover bolt then i think there would be some serious issues .. it still can be but i don't remember a washer as part of these bolts . I think a bolt here would also stay in the head . Granted it's been a long time since ive done an engine rebuild though . If i'm correct then it can be left and not worry about .. if your correct then i would want to strip the cam covers and find out to be honest as i'm worried just thinking about it . No offence young man .. i rarely question what other people post here as we all have our own opinion .. its just i think we need to get to the bottom of this and i never have a problem with being wrong . More suggestions please .. infrasilver your thoughts ?

I've been through my engine internal pictures and the only socket heads I can see are the cam and tappet chest, these all have an integrated washer but they will struggle to get to the sump but its not impossible? But if I remember these are all over 25mm long. It think is foreign to the engine with having a waisted end.

I have a feeling the ones in the 3.4l are 30 or 35mm long, definately with washer. I think one of those is most likely to. MC

Thanks for all the thoughts on this. It is hard to measure it as the head is bent around but I'm pretty sure it would have been 25mm inc. the waisted end. If it is a foreign bolt that is too short for where it was supposed to be that might explain it coming loose. Assuming it was used as a cam or tappet chest bolt, how much room is there in that area for a bolt to wind all the way out?

The bolt length is measured from under the head or washer, to the end of the thread, so this excludes the head length :thumb: Standard sizes would be 8mm, 12mm, 16mm, 20mm, 25mm and 30mm and so on in 5mm increments :grin:

The tappet chest bolts can wind out all of the way, there is easily enough room. They are the bolts in the above picture sat back in the base of the head. I've edited the picture to circle those bolts

To me the marks all look similar in impact. Which would mean it struck the same thing multiple times. There all a V type strike. Also quite a small V given the size of the bolt. likely the timing chain?