Big hole in crank casing-new engine needed or repair?

[onionbargee]

Possibly, if the con rod snapped. Not sure I've ever seen one snap though.

 

But musing about the sequence of events, if the big end bolts came loose and the and cap fell off, the piston would have been battering the valves for quite a while before the failure. And the engine would have sounded appalling while that was going on!

 

If the bolts both snapped suddenly, I can't imagine what might have caused that. If the con rod snapped and made the nice window, I'm not sure why or how the cap came off, It should still be attached to the crank.

 

I seem to remember not long ago you said on this very forum you didn't know anything about Diesel engines ?

Edited April 21, 2015 by onionbargee

[MoominPapa]

If the bolts both snapped suddenly, I can't imagine what might have caused that.

Seized piston? Normally the big loads on a conrod are compressive, so don't affect the cap bolts. If the piston seized at or near the top of the bore then the crankpin will be trying to pull the stuck piston downwards, via the cap and bolts. I guess it depends if a piston can seize that hard and that fast.

 

The other possibility is that the conrod snapped, and the failing end smashed the hole and simultaneously smashed itself off the crankshaft.

 

Anyway, to quote RLWP after I described the inards of my gearbox to him: "It's knackered".

 

MP.

 

[the barnacle]

Duck tape there isnt much it cant fix

[MtB]

I seem to remember not long ago you said on this very forum you didn't know anything about Diesel engines ?

 

You're right. But I bet you can't produce a link!

 

 

Seized piston? Normally the big loads on a conrod are compressive, so don't affect the cap bolts. If the piston seized at or near the top of the bore then the crankpin will be trying to pull the stuck piston downwards, via the cap and bolts. I guess it depends if a piston can seize that hard and that fast.

 

The other possibility is that the conrod snapped, and the failing end smashed the hole and simultaneously smashed itself off the crankshaft.

 

Anyway, to quote RLWP after I described the inards of my gearbox to him: "It's knackered".

 

MP.

 

 

The other situation is in an an over-revving engine. The bolts are in tension as they slow the piston down to a stop as it approaches the top of the exhaust stroke.

 

This engine could have been drinking it's own oil and run away. That would explain everything.

[Guest]

 

You're right. But I bet you can't produce a link!

 

 

 

The other situation is in an an over-revving engine. The bolts are in tension as they slow the piston down to a stop as it approaches the top of the exhaust stroke.

 

This engine could have been drinking it's own oil and run away. That would explain everything.

Saw a two stroke engine once that had done similar. I think you theory of run away is a strong possibility.

[MtB]

I like your sig.

 

Very true and explains most of the angry posts/posters on here.

[system 4-50]

This is so frustrating! I want to know what it looks like inside, I want to know what happened, I want to hear from the bystanders, did the people present get counselling, have they got closure yet, tell me more!

[MtB]

Well the OP hasn't signed back in since posting his OP. And I have a sneaky feeling he never will, given he has only ever posted twice.

 

You could always nip over to Bristol and hunt him down. Take photos and update us!

[AndrewIC]

You could always nip over to Bristol and hunt him down. Take photos and update us!

He won't be going anywhere...

[Guest]

I like your sig.

 

Very true and explains most of the angry posts/posters on here.

It is tactical

[matty40s]

I seem to remember not long ago you SAID on this very forum you didn't know anything about Diesel engines ?

Even Mtb can tell that is broke a bit.

He won't be going anywhere...

The next post will be in two weeks -

"BowHauling up the Severn - what do we need to know"

[Arthur Brown]

Can one surf a NB on the severn bore?

 

The whole thing reminds me of the student T-shirt - Engine trouble, Piss*d 'n Broke

[onionbargee]

4108 's are cheap as chips anyway. Plenty on fleabay.

[Chalky]

Seized piston? Normally the big loads on a conrod are compressive, so don't affect the cap bolts. If the piston seized at or near the top of the bore then the crankpin will be trying to pull the stuck piston downwards, via the cap and bolts. I guess it depends if a piston can seize that hard and that fast.

 

The other possibility is that the conrod snapped, and the failing end smashed the hole and simultaneously smashed itself off the crankshaft.

 

Anyway, to quote RLWP after I described the inards of my gearbox to him: "It's knackered".

 

MP.

 

 

I've seen it happen on super charged petrol engines. High levels of boost cause the piston to get hot however the throttle disk is open and lots of air is coming in so keeps it cool. As you slow down the air flow stops, the heat builds up and the engine starts to loose power. Very quickly the piston seizes in the bore. The inertia of the engine tries to keep the whole lot going and breaks the little end/piston/gudgeon pin. The rod then flails round wrecking the piston and bore till it tilts over and starts hammering at the crank case. Result - 1 scrap engine.

[cuthound]

The last time I saw a hole that big in a crankcase was in my rallying days, back in the 70's. A friend had a Broadspeed Bullet, a turbocharged 3 litre Ford Capri. They had "decompression plates" fitted, (like a thicker head gasket) to reduce the compression ratio.

 

He removed them and replaced them with standard head gaskets, then entered a road rally. The engine lasted only until he gave it some beans, then a piston, still with conrod attached, escaped through the side of the block.

 

In the club magazine his non finish was described as " electrical failure - conrod smashed the battery".

[Guest]

The last time I saw a hole that big in a crankcase was in my rallying days, back in the 70's. A friend had a Broadspeed Bullet, a turbocharged 3 litre Ford Capri. They had "decompression plates" fitted, (like a thicker head gasket) to reduce the compression ratio.

 

He removed them and replaced them with standard head gaskets, then entered a road rally. The engine lasted only until he gave it some beans, then a piston, still with conrod attached, escaped through the side of the block.

 

In the club magazine his non finish was described as " electrical failure - conrod smashed the battery".

Like it

[staszekimogen]

hi all,

 

Firstly thanks for everyones good advice about the engine, we are now looking at sending it to a perkins reconditioner and getting it rebuilt as this seems the best course of action for us, and also comes with a 12month guarantee. We will get this work done before leaving the marina...

 

Can i also mention that its not necessarily helpful for people to assume what we do or dont know about the boat- yes we have been slow to reply but buying a boat is time-consuming as you probably all know! We were fully aware of the engine fault before we bought the boat and the price reflected this and we have had a glowing hull survey so happy days!

 

I thought it would be good to post and get some more opinions than the ones we already had and also to get a feel for the forum.... to be honest though some people could try keeping their advice constructive rather than giving negative opinions!. Thanks to 'catweasel' for standing up for us and pointing out that everything is replaceable/repairable and some of us are up for a challenge and can't afford to buy expensive perfect boats!

 

thanks again all

[Stilllearning]

Are you sure that's an economically reconditionable engine?

[alan_fincher]

hi all,

 

Firstly thanks for everyones good advice about the engine, we are now looking at sending it to a perkins reconditioner and getting it rebuilt as this seems the best course of action for us, and also comes with a 12month guarantee. We will get this work done before leaving the marina...

 

Thanks for the update.

 

I must admit, though, that as working examples of these engines seem to sell quite cheaply, whereas several past threads have commented on the huge costs of far less drastic repairs to other Perkins engines, it does surprise me that that this is likely to be the best way forward.

 

However, good luck, with whatever you decide to do.

[RLWP]

Are you sure that's an economically reconditionable engine?

 

No, it isn't. It won't qualify as an exchange unit either

 

Richard

[Bod]

Are you sure that's an economically reconditionable engine?

 

Its under a 12 month guarantee.

Would be interesting to know the cause, and full extant of the damage.

 

Bod

[Naughty Cal]

 

Its under a 12 month guarantee.

Would be interesting to know the cause, and full extant of the damage.

 

Bod

Not at the moment it isn't. It would be if reconditioned. Although this seems very unlikely!

[John Williamson 1955]

Not at the moment it isn't. It would be if reconditioned. Although this seems very unlikely!

I read Bod's post to mean that it has failed within the 12 month warranty from when it was last rebuilt or was supplied to him. In which case, it doesn't matter whether it can be rebuilt or not, it's the supplier's problem and responsibility to provide a working engine under the warranty. (Assuming it's a decent warranty, and not a cheap insurance based deal....)

[Naughty Cal]

I read Bod's post to mean that it has failed within the 12 month warranty from when it was last rebuilt or was supplied to him. In which case, it doesn't matter whether it can be rebuilt or not, it's the supplier's problem and responsibility to provide a working engine under the warranty. (Assuming it's a decent warranty, and not a cheap insurance based deal....)

 

hi all,

 

Firstly thanks for everyones good advice about the engine, we are now looking at sending it to a perkins reconditioner and getting it rebuilt as this seems the best course of action for us, and also comes with a 12month guarantee. We will get this work done before leaving the marina...

 

Can i also mention that its not necessarily helpful for people to assume what we do or dont know about the boat- yes we have been slow to reply but buying a boat is time-consuming as you probably all know! We were fully aware of the engine fault before we bought the boat and the price reflected this and we have had a glowing hull survey so happy days!

 

I thought it would be good to post and get some more opinions than the ones we already had and also to get a feel for the forum.... to be honest though some people could try keeping their advice constructive rather than giving negative opinions!. Thanks to 'catweasel' for standing up for us and pointing out that everything is replaceable/repairable and some of us are up for a challenge and can't afford to buy expensive perfect boats!

 

thanks again all

 

Reading the above quoted post wherever it is they are planning on getting it repaired that is offering the 12 month warranty on the repaired engine.

[John Williamson 1955]

 

 

Reading the above quoted post wherever it is they are planning on getting it repaired that is offering the 12 month warranty on the repaired engine.

Ah yes, I must pay more attention. In which case, when the reconditioner sees it, there'll be a surcharge for at least a new block and crankshaft. Or, to put it another way, they'll just supply a new engine and may deduct the scrap value of the old one from the bill.