S52 HAMMERED spark plug, possible rod knock!?!?

[Grimm5698]

So I've done some research trying to figure out a spark plug issue but haven't found anything on what might be the cause.
Long story short my friend recently bought a sedan e36 M, car has been running great not even a week into ownership and all of the sudden started miss firing and trying to die not holding idle.
We did some diagnosis cleaned the ICV and pulled the spark plugs and coils, all looked good but cyl.6 . Seems like the spark plug got hammered possibly by the piston but not sure at the moment as we need to check the cylinder and piston head with a endoscope camera. The ceramic is missing but the ground electrodes are all there.
Never seen this happen before, anyone have experience with this or any idea what might have caused this?
Any info is helpful, still have to do more diagnosis on the engine to see what happened.Screenshot from 2017-11-17 22-53-10.pngScreenshot from 2017-11-17 22-53-18.png

[AlpineM3OldAsMe]

Are those quad electrode? I've never seen it personally but I've read of those plugs failing in that manner. Should be easy to see if it made contact with piston. Make sure to check your torque specs on all your plugs these aluminium threads are really finniky with the plugs

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[Twright]

Make sure that those are the correct plugs and not ones that stick down too far into the cylinder.

[RRSperry]

I know I'd be scoping that cylinder. Id also be doing a compression and leakdown test.

[pbonsalb]

Looks like a foreign object got in there or a mechanical over rev, aka moneyshift, bent a valve and maybe broke a piece off that became a foreign object. I agree with sticking an inspection camera down the hole or doing a compression test to see how that cylinder matches the other 5. I think these cars used 2 prong plugs from the factory and don’t think 4 prong plugs will hurt as long as they are not extended tip and that plug does not look like extended tip.

[bluptgm3]

As I recall the factory Bosch plug was a copper core four electrode plug.


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[TH3 Shifty]

single prong coppers are much better than any of this platinum irridium plutonium 85 prong crap..

[fbmbirds]

single prong coppers are much better than any of this platinum irridium plutonium 85 prong crap..

This

[Grimm5698]

Update! So finally got a chance to get a endoscope cam in cylinder 6, looks good piston and cy. walls look undamaged. Tried turning the engine over by hand but everytime cy.6 got to TDC it would lock up, ended up using a mirror adapter on the endoscope cam to see if maybe a valve had fallen out and to my amazement found a chunk of metal that got banged into
the cylinder head
Screenshot from 2017-11-22 01-57-00.pngScreenshot from 2017-11-22 01-57-17.png
so when the piston is at TDC that metallic piece is preventing the piston from going up and jamming up between the head and piston head still have no idea what happened or what caused that to happen. I'll be pulling the engine and taking the cy. head and oil pan off to inspect the rods, replace the leaky oil pan gasket and hopefully the head is salvageable but from the looks of it, it might not be I'll keep this thread updated with results and pics of the process.

[Grimm5698]

AlpineM3OldAsMe - Yes those are quad electrode plugs the PO was running, as of now only cy.6 plug got damaged

Twright - I checked the part # on the plug and yep Its OEM plug

RRSperry - Coulnd't do a comp test as the piston is locking up so pulling the head off this weekend

pbonsalb - yep sure does look like something got in there, waiting to see what the metal piece is once I get the head off

bluptgm3 - that is correct, based in the part# on the plug

[pbonsalb]

Member butters stoch had a similar issue. Found a screw smashed into the chamber. He pulled the head, removed the screw, polished the chamber a bit and reused the head.

[mitch500]

In for the results!


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[Grimm5698]

So finally got a chance to take apart the engine in my friends e36, and boy were we surprised by the findings , Looks like cy.6 took a beating for who knows how long and the cylinder head is eaten up and possibly melted too, apart from that we found a chunk of metal about 2mm x 4mm in cy.6 which would explain the bent intake valves on that cylinder. Still have no idea what could have caused this catastrophic failure, car was running fine, idle was perfect no vanos rattle or knocking. Just all of a sudden some rough idle followed by knocking as the car coasted to the side of the road . Still puzzled on what may have caused all this, to me it seems someone tried to rebuild the engine at one point and did shoddy work because cam cap 7 on the intake side was flipped around facing driver side and every other cam cap was facing pass side caps showed marring on them too, also the head gasket that was used was a victor reinz and did have burn marks between the cylinders and I have heard of these specific VR gaskets failing so thats another thing to consider. Engine is too far gone to rebuild, it would need a new head and a rebore along with new pistons which would take even more material out of the s52's thin walls. I gave some options to my buddy about what to do from here and he's decided to do a base m52 turbo build so currently looking for a donor car, another s52 laid to rest

Screenshot from 2017-11-29 01-08-48.pngScreenshot from 2017-11-29 01-09-20.pngScreenshot from 2017-11-29 01-09-38.pngScreenshot from 2017-11-29 01-09-58.pngScreenshot from 2017-11-29 01-10-17.png

[TH3 Shifty]

why would it need an over bore? are the cylinder walls scored? the head is &%$# yes and the piston.

[pbonsalb]

I doubt anyone tried to rebuild the motor. More likely a very amateur mechanic head gasket change. He probably is responsible for the foreign object -- maybe something fell into the intake manifold.

I have read of people swapping in a used piston with new rings. I probably would not do it unless I was on a very tight budget and had lots of free time to do t he job over again if necessary.

There is a $1200 low mileage S52 with thicker HG already installed for a turbo project for sale now in the classifieds. Looks like a very fair deal to me. But an M50 or M52 is also a great budget motor since they are about $500 used. The lower displacement does not spool a turbo as well, but sometimes your budget does not allow all of the best parts (like an S52 instead of an M52).

[rajicase]

You do know people are making 800+ whp on 87mm s52s. Bore and hone this s52 and put 86.5mm or 87mm pistons in it if you are going turbo. S52 is a much, much better engine for boost. Look at some dyno graphs of m5x vs an s52 with similar set up. Power band and torque curve along with over all torque is much better in the s52.

- - - Updated - - -

I have an 86.5mm S52 and am making north of 600whp currently. Unless you want 1000whp I wouldn't even consider wall thickness...

[Grimm5698]

My friend found a wrecked donor car for dirt cheap and has a m52 and ZF in it
he's picking it up this weekend and were gonna swap it into his current e36,
possibly swapping the s52 cams into the replacement m52 for the extra hp

TH3 Shifty - Yep cylinder 6 has some pretty deep scoring

pbonsalb - Yea, most likely a headgasket job gone wrong.
My friend did consider buying a used s52 piston, doing some slight
honing with the ball hone tool and throwing it in but the cylinder
wall is pretty scored and would have to bore all the cylinders and
use new pistons $$$$

rajicase - yea that's true I have seen a couple boosted s52 builds, just easier
to source a m52 if things go wrong .