28 replies to this topic

[Muncher]

"ineedtheturbo" very kindly gave me his old engine after it went bang in spectacular fashion whilst in Europe so today I stripped it down to salvage a few bits from it and also to have a general play to see if I could work out what went wrong.

The 2 big holes in the block and one in the sump suggested it was quite serious

Having fully stripped it as far as I could tell it looks as though one of the conrods snapped, blowing a hole through the block. The piston only made very minor contact with the valves on one cylinder meaning the head is fine.

There was a lot of soot on the pistons which I guess suggests it was using a lot of oil? Everything else from what I could tell seemed fine, the timing chain was fine, the crank bearings didn't look that bad, it just looks as though the conrod snapped in two places...

http://www.muncher.o...22se_postmortem

There's 70 odd pics there so hopefully enough for the engine gurus to go on...

[drew]

hi m8. what power was this motor running. D

[Muncher]

Standard or not far off standard power. I guess about 65k.

[techieboy]

hi m8. what power was this motor running. D

From memory just about standard but no/low oil followed by a bang.

Jeez, Muncher, I saw the thread title and that picture and thought for a horrible moment you'd just killed your new SC conversion. Phew!

[slindborg]

Looks like it was consuming oil, and also there looks to be mega det marks on the pistons.... would appear to be a few reasons as to why it decided not to like its legs anymore Have to say, the block has stood up well to it though!!!!

[daggles]

The end cap is broken in half so my guess would be a big end bolt let go at high rpm. Eventually after a period of loud knocking (brief if you are still driving it) either the other bolt will go or the end cap will break in half. I'd guess the rod was broken as it was mangled by the crank.

[matt_b]

The big end bolt thats still in place, is it still at its correct torque? I reckon it may have worked a bit loose giving the rod fraction of up and down movement on the crank pin which has increased the stress across to break point and its eventually fatigued and failed. If you could get some high res pics of the failure area close up then it should tell the whole story. What was the circumstances of the failure? Was it at high rpm in a track day scenary or more of a leisurely drive?

[vocky]

the z22se has two main problems which kill the engine number one cause of engine failure = 'old spec' small oil jet can block number two cause of engine failure = a low engine oil level causes the conrod to fail there is possibly another problem, the oil pump pressure relief valve can stick, if it sticks closed you get high oil pressure, if it sticks open you get low oil pressure

[cheeky_chops]

Put the block on ebay and see if you get any bids!

[Muncher]

Just had a mate who's an technician at Ford look at those pics and he's convinced it's not really down to oil level. He thinks it has been over revved and the con rod has simply failed.

[slindborg]

Just had a mate who's an technician at Ford look at those pics and he's convinced it's not really down to oil level.

He thinks it has been over revved and the con rod has simply failed.

when you say technician.... do you mean dealer spanner monkey?
or engine builder?
or engine designer?


given the level of sever spankage the Z22SE sees on here, I really really cant see that fail being a revs related issue (unless ineedaturbo was lying about when/how it failed), although a keen downshift could have caused it.

What does the head look like, valves etc?

[Muncher]

Not a dealer spanner monkey or an engine designer but somewhere in between with over 20 years of experience. The heads is fine and there is no wear on the cam bearings which would be the first to show signs of wear if there was sod all oil.

[matt_b]

Just had a mate who's an technician at Ford look at those pics and he's convinced it's not really down to oil level.

He thinks it has been over revved and the con rod has simply failed.

As I say, if you can get a closer up picture of the two sides of the failed area then it will be possible to work back and see what forces were at play to cause the failure and then use this to determine the real world cause. It could just be over-revving, but that sounds like the 'easy option' diagnosis - if it was down to purely over-revving then I would really expect there to be some sign of stretch on the bolts as for the rod to fail these would have been close to failure...

[slindborg]

Not a dealer spanner monkey or an engine designer but somewhere in between with over 20 years of experience.

The heads is fine and there is no wear on the cam bearings which would be the first to show signs of wear if there was sod all oil.

I mean are the valves fully shut with the cams out...(dont really give a toss about cam bearings lol).

not enough pics for an accurate cause of death/chain of events. Need more info from when it died too e.g. what was the engine doing.
As the rods are nearly 50% "stronger" than they need to be for running std power (yes stage N/A remaps are still std power lol) and real overrevving would have properly mangled the life out of the block/piston (would have been a ball of aly rather than a solid, in tact piston shape), I dont honestly believe it was an over rev.

chances are it was either down on oil or a simple freak fail, but those pistons do look heavily carboned up and there are hints of det on them. pics of the underside of the head will help

[Muncher]

I've left the cams in. The underside of the head looked much like the surface of the pistons, no discernable damage.

[Mike-F]

Do you have a close up of the upper fracture, may be possible to tell if the fracture was there for sometime. If there are noticble beach marks in the fracture then it may have just been a faulty rod, with a fatigue fracture spreading across the rod.

[Muncher]

Do you have a close up of the upper fracture, may be possible to tell if the fracture was there for sometime. If there are noticble beach marks in the fracture then it may have just been a faulty rod, with a fatigue fracture spreading across the rod.

I'll go and take some close up pics of the rod tomorrow and maybe the underside of the head.

[slindborg]

I've left the cams in. The underside of the head looked much like the surface of the pistons, no discernable damage.

chances are, the head will need new guides in the cylinder that failed. You can see the piston hit the valves in the pics. This usually cracks the guides a treat.

[Muncher]

I've left the cams in. The underside of the head looked much like the surface of the pistons, no discernable damage.

chances are, the head will need new guides in the cylinder that failed. You can see the piston hit the valves in the pics. This usually cracks the guides a treat.

Yeah, I'm just going to flog it, if I can get back the £50 the engine stand cost me and have a pair of balancer shafts for vocky to machine down I'll be happy

[snowwhite]

Very interesting The big end bearing looks alright doesn't appear to have over heated due to oil starvation. No1 has definitely hit the valves though! Will wait for more pics and confirmation of circumstances before I make up my mind