S3 2.25 petrol BANG! Help/opinions/yada please?

Castor · Jul 25, 2023

I haven't been here for a while......

So I'm at the lights, half a mile from home - I move off and there is a terrific bang just after I change into second, and the transfer box is suddenly in a neutral, gears grinding like crazy. Engine continues to run - it idles but lumpy. Good oil pressure.
I re-engage 2wd as before, and we proceed the half-mile back home. Slowly, trailing smoke.......
Findings: No 3 cylinder. 2 very bent pushrods. Head looks superficially OK but I haven't dismantled yet.
And this. WTAF could cause *this*??
I haven't explored the bottom end yet - that should be fun!

I'm taking bets on how recoverable this is. Has the liner survived? Where's the con-rod??

kermit_rr · Jul 25, 2023

Blimey!!

kermit_rr · Jul 25, 2023

The block doesn't have liners but may need a rebore, depending on any damage/how much

Castor · Jul 25, 2023

kermit_rr said:
Blimey!!

That's what I thought.......

marjon · Jul 25, 2023

Thats an opps :vb-groan2:

Its almost as if the little end has come apart then hooked back up but in a position to push the piston further up (hence the head shape replication).

Have you tried to get hold and pull it out, if you do I suspect it will come out. If you turn the engine over does that move? I suspect not

But do let us know what you find .

J

Castor · Jul 25, 2023

kermit_rr said:
The block doesn't have liners but may need a rebore, depending on any damage/how much

It's a voyage of discovery.....

Castor · Jul 25, 2023

marjon said:
Thats an opps
Its almost as if the little end has come apart then hooked back up but in a position to push the piston further up (hence the head shape replication).

Have you tried to get hold and pull it out, if you do I suspect it will come out. If you turn the engine over does that move? I suspect not

But do let us know what you find .

J

Weird, innit? It still ran.
I'll have another session later and get the bottom end exposed.

marjon · Jul 25, 2023

Castor said:
Weird, innit? It still ran.
I'll have another session later and get the bottom end exposed.

Most engines will run with 1 cylinder not working, lumpy/different but drivable.

Good luck. I suspect the block will be ok (hope).

J

kermit_rr · Jul 25, 2023

marjon said:
Most engines will run with 1 cylinder not working, lumpy/different but drivable.

Good luck. I suspect the block will be ok (hope).

J

even the discovery v6 will run with a completely snapped crank

Castor · Jul 25, 2023

marjon said:
Most engines will run with 1 cylinder not working, lumpy/different but drivable.

Good luck. I suspect the block will be ok (hope).

J

I wonder what the conrod was doing....

marjon · Jul 25, 2023

Castor said:
I wonder what the conrod was doing....

There's only 1 way to find out

, See if you can pull it out might save a lot of mess in deciding if its toast or not.

J

kermit_rr · Jul 25, 2023

Castor said:
I wonder what the conrod was doing....

have you ever seen a lamb on a nice, warm, spring day?!

kermit_rr · Jul 25, 2023

marjon said:
There's only 1 way to find out , See if you can pull it out might save a lot of mess in deciding if its toast or not.

J

yes probably better coming out via the top, if it will

BikerB · Jul 25, 2023

Its is amazing what is recoverable, as long as the block and crank are intact.
I an vouch that missing a cylinder on a 4 pot doesn't stop it driving as long as it isn't locked up.
I once drove from North of Inverness to Glasgow in an MGB with a hole clean through the top of one piston, it usd a lot of oil, smked like buggery and only did 30mph but it got home.
That engine was later rebored and rebuilt as a 1950cc from the original 1800cc with no more than the machining and a new set of pistons and shells.
As long as the major parts are in one piece you should be fine, although I agree, try and see if the piston comes out the top and you will probably see the broken piston. the little end and rod may be OK.

Castor · Jul 25, 2023

kermit_rr said:
have you ever seen a lamb on a nice, warm, spring day?!

Castor · Jul 25, 2023

Castor said:

BruceB said:
Its is amazing what is recoverable, as long as the block and crank are intact.
I an vouch that missing a cylinder on a 4 pot doesn't stop it driving as long as it isn't locked up.
I once drove from North of Inverness to Glasgow in an MGB with a hole clean through the top of one piston, it usd a lot of oil, smked like buggery and only did 30mph but it got home.
That engine was later rebored and rebuilt as a 1950cc from the original 1800cc with no more than the machining and a new set of pistons and shells.
As long as the major parts are in one piece you should be fine, although I agree, try and see if the piston comes out the top and you will probably see the broken piston. the little end and rod may be OK.

B series Morris Oxford, Leeds to Teesside once with a crank which came out in two pieces.

Castor · Jul 25, 2023

BruceB said:
Its is amazing what is recoverable, as long as the block and crank are intact.
I an vouch that missing a cylinder on a 4 pot doesn't stop it driving as long as it isn't locked up.
I once drove from North of Inverness to Glasgow in an MGB with a hole clean through the top of one piston, it usd a lot of oil, smked like buggery and only did 30mph but it got home.
That engine was later rebored and rebuilt as a 1950cc from the original 1800cc with no more than the machining and a new set of pistons and shells.
As long as the major parts are in one piece you should be fine, although I agree, try and see if the piston comes out the top and you will probably see the broken piston. the little end and rod may be OK.

OK, I've got the piston knocked back down 3/4" and the bore up top looks ok. I now need to cobble some sort of puller.
Does anyone know how thick the piston crown is?

marjon · Jul 25, 2023

Castor said:
OK, I've got the piston knocked back down 3/4" and the bore up top looks ok. I now need to cobble some sort of puller.
Does anyone know how thick the piston crown is?

Turn the engine over push it back up and a few self tappers in it to get a hold of, I bet you can pull it out.

The bottom has to come off anyway, I was saying take it out from what you had as you had something to get hold of.
Plus then we can all see whats happened

.

J

LordOWar · Jul 25, 2023

Never seen a piston mould itself into the shape of the combustion chamber before. 10/10 for style and panache! I bet there will be more damage to the bore lower down.

Castor · Jul 25, 2023

LordOWar said:
Never seen a piston mould itself into the shape of the combustion chamber before. 10/10 for style and panache! I bet there will be more damage to the bore lower down.

I'm still excavating. Trust me to find a new failure mode.....

S3 2.25 petrol BANG! Help/opinions/yada please?

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