Bought a 2000 Boxster S engine project
 

Saw this engine on Facebook Marketplace. When the prix came down to $500 (CDN) I couldn't resist... I figure it will be a winter project to keep me busy.
It will not do a full revolution with a wrench on the crankshaft bolt, it turns till it doesn't. It is possible to turn it back so it is not seized. The seller bought it to rebuild, doesn't know the history and he sold his Boxster so wanted it gone.
I figured it could be a case of piston meets valve and it looks like I was right...
You can see the stub of a broken cylinder 3 exhaust valve on the right.

http://986forum.com/forums/uploads02...1761849778.jpg

So I'll get that head off soon to see if the engine can be saved.
There was no glitter in the oil pan and the filter looks OK, I haven't as yet cut the filter open but a quick look didn't reveal anything.

I did find this coil pack...

http://986forum.com/forums/uploads02...1761850293.jpg

After prying it out I saw this!

http://986forum.com/forums/uploads02...1761850333.jpg

A regular spark plug tube is beside it and there is no relation between the two. I understand why it might have leaked.

Upon closer inspection both exhaust valves are broken in cylinder 3. The cams are out and I found this strange material on the timing gear. It is very hard and not metallic.

http://986forum.com/forums/uploads02...1761856065.jpg

Looks like a sealant or repair material. It has been there for at least some revolutions. I found some small pieces of the same material in the oil pan.

http://986forum.com/forums/uploads02...1761856036.jpg

I can't think of anything that is supposed to be in the engine that would look like this.
I don't see how this could have caused the broken valves. I would think that the chain tensioner would absorb the extra tension as the blob passed under the chain. It would be nice to know if the chain had jumped a tooth or two...

Looks like a piece of a chain pad jammed in between the teeth and the chain.

Imagine what that debris would do to your valve timing! No wonder you have valve contact and big wonder it didn't take out more.

The same idea came to my mind, the chain may have "jumped"...

I don't think so. It is rounded like a liquid or semi-liquid which has hardened... I've seen a lot of pieces of chain pads and it is not the same.

... EDIT - I think you are right, see the photo in the next post.

I removed the tensioner and found this chain pad...

http://986forum.com/forums/uploads02...1761917541.jpg

The blob that was on the gear (although I guess it is more correctly called a sprocket) appears to be the right size to be the missing piece of the pad. It is so deformed that there is no surface that lines up with the rest of the pad.

Since this is the only anomalie that I have found so far it would seem to be the source of the broken valves... but I am having difficulty visualising how a double row chain with about 75% contact on the timing sprocket could skip because one link is not making contact.

Should not have doubted Homeoboxter.

I would guess that the engine has at more than 100K miles on it. On other engines that I have disassembled, with less than 100K miles the pads were worn but not broken. In my opinion if the pads have not been updated at 100K miles it is definitely time to do it. This question is not discussed enough on forums that deal with the M96 Boxster and 996 engines.

This will not buff right out!
 

This may not be the best deal I have ever made. Head off and this is what I found...

http://986forum.com/forums/uploads02...1761933712.jpg

Every valve on bank 1 hit a piston judging from the marks on the pistons, all the exhaust valves are bent to the point where they will not close, and some of the intake valves.

http://986forum.com/forums/uploads02...1761933771.jpg

The head is toast... note that the exhaust valve on the right broke and then the stem was driven into the head beside the valve guide. Ouch.

http://986forum.com/forums/uploads02...1761933835.jpg

... and the engine will still not turn over so the other bank may be problematic also. Maybe the short block is salvageable???

Maybe not the best deal, still an interesting project :cheers:

Ya...
The other head is off and that side looks fine. Unfortunately I still cannot make a full revolution of the crankshaft, it blocks when the bad piston, #3, is almost at the bottom of the stroke. I think perhaps the rod is bent or some such. Too bad, the engine looks like it was in good shape, no bore scoring and the only marks on the cylinder walls are cylinder 3 where the debris left a few scratches.

CHANGE YOUR TENSIONER CHAIN PADS!!!!

Yes indeed. I’ve had two apart, one of 106,000 miles and the other indeterminate, and both had wear pads like this. And the former wrecked the nine when the debris blocked the oil pickup, taking out a cam and main bearing. I’m a little worried regarding the condition of my 99 with 76,000 miles!