Member Since: 28 Dec 2018
Location: Cradley Heath
Posts: 382
Unusual snapped crank
Hi folks,
Anybody taking part in my snapped crank sweepstakes might be interested to learn about a new type of snap. As you can imagine, we see a lot of snapped cranks. But they have all snapped in the same place; between #2 big end and #2 main. This is where the crank is the thinnest...
Now however, I've just come across a snap on the front counterweight where the metal is the thickest.
Here you can see the 2 types of snap compared.
This has come out of an engine we rebuilt over 2yrs ago and had done 36k miles. The crank was reground to .25mm across the board at the time of the rebuild and had a 0.5mm rebore with new rods & pistons. The crank, rods, pistons, flexiplate, front damper & pulley all balanced as a set. Strip down of the oil pump showed no signs of wear or scoring, so was working properly. No bearings had turned and showed normal wear. Fuel injectors tested and all working within specifications at time of snap. Car was serviced by us every 6k miles using Castrol Edge Pro 5w30 C1
It just goes to show that no matter what you do and how well you look after your engine, can happen at any time.Joe
19th Feb 2019 9:07 am
Beretta
Member Since: 11 Oct 2012
Location: Rochdale
Posts: 1180
That very worrying!2010 Disco 4 HSE
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19th Feb 2019 9:10 am
robpenrose
Member Since: 12 Jan 2016
Location: Surrey / SW London
Posts: 2136
Has this crank gone in a different way because it’s been rebuilt? Have you had many engines come back after a rebuild with another snapped crank?
It would be interesting to know what sort of mileage people are getting after an engine rebuild before the engine goes bang again? I can’t believe these engines are such a lottery!!!
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26th Mar 2019 9:24 am
OvalAutos
Member Since: 28 Dec 2018
Location: Cradley Heath
Posts: 382
No, I don't think it was anything to do with the rebuild we did. The engine was running perfectly and everything checked out. Like I said, I've not seen one like this before.
As to the life of a rebuild, this is the only example where I know the history of the engine. We do get jobs in where the engine has had a recon and failed, but the owner is new and didn't know the engine had been done in the past, so no idea of mileage.
We service cars with 200k miles on the original engine and, god knows how, still have the original timing belt
We have 3yr old cars with dealer service, 30k miles and failed engines
It really seems like a lottery to me; you're either lucky or notJoe
26th Mar 2019 9:52 am
L319
Member Since: 14 Dec 2013
Location: Herefordshire
Posts: 2080
Looking at the break, I wonder if its the result of the regrind of the crank . The radius, journal to the web, its a classic stress raiser, has to be very precise and it has broken at that point.
26th Mar 2019 9:59 am
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8069
I think JLR have got the same problem as Boeing , it’s just got to be a bug in the software, if one injector injects fuel once in an advanced stage and it fires before the piston reaches TDC it is equal to having water in the cylinder and everybody knows what that does, and it happening twice to the same vehicle might confirm this.
My condolences to the owner and yourselves if it costs It can when others can't,
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26th Mar 2019 12:01 pm
Russell
Member Since: 24 Aug 2007
Location: Kent
Posts: 10564
Why was the car serviced evey 6K, that seems a little odd, or is it just that the car only cover 6K a year although that does not add up with the mileage and re-build infoMY17 D5 1st Edition Namib Orange
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26th Mar 2019 11:52 pm
PCT3
Member Since: 13 May 2017
Location: Kent
Posts: 144
M3DPO wrote:
I think JLR have got the same problem as Boeing , it’s just got to be a bug in the software, if one injector injects fuel once in an advanced stage and it fires before the piston reaches TDC it is equal to having water in the cylinder and everybody knows what that does, and it happening twice to the same vehicle might confirm this.
My condolences to the owner and yourselves if it costs
There may be mileage in that thought, we build and refurbish classic trials cars, they use ford e93a and 100e engines, as you can imagine there’s not many left and even fewer spares, so our engine rebuilds are all very custom ensuring that components are as close as possible to perfection, free flow exhausts twin SUs then when in compertion revs you wouldn’t believe an old side valve engine could do, never a broken crank worse we have had a big end picking up.
Miss injection timing there’s a thought.Discovery 3 HSE 07
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27th Mar 2019 12:41 am
OvalAutos
Member Since: 28 Dec 2018
Location: Cradley Heath
Posts: 382
Russell wrote:
Why was the car serviced evey 6K, that seems a little odd, or is it just that the car only cover 6K a year although that does not add up with the mileage and re-build info
It was the customer's choice to have an oil change every 6k miles. He was a bit worried because of the first failure (big end) and wanted a belt & braces plan.Joe
28th Mar 2019 9:00 am
OvalAutos
Member Since: 28 Dec 2018
Location: Cradley Heath
Posts: 382
PCT3 wrote:
M3DPO wrote:
I think JLR have got the same problem as Boeing , it’s just got to be a bug in the software, if one injector injects fuel once in an advanced stage and it fires before the piston reaches TDC it is equal to having water in the cylinder and everybody knows what that does, and it happening twice to the same vehicle might confirm this.
My condolences to the owner and yourselves if it costs
There may be mileage in that thought, we build and refurbish classic trials cars, they use ford e93a and 100e engines, as you can imagine there’s not many left and even fewer spares, so our engine rebuilds are all very custom ensuring that components are as close as possible to perfection, free flow exhausts twin SUs then when in compertion revs you wouldn’t believe an old side valve engine could do, never a broken crank worse we have had a big end picking up.
Miss injection timing there’s a thought.
Fuel injectors are something we religiously check to see if they are operating within specification. A high or low fueling or bad spray pattern injector is going to give the engine an imbalance. When we strip down failed engines, the injectors are tested and most of the time we see a correlation with a failed big end and faulty injector. In some cases, other injectors are also out of spec, but not failed a big end. It's not a definite cause, but does give some food for thought.Joe
28th Mar 2019 9:08 am
adam
Member Since: 20 Sep 2005
Location: Home and Happy
Posts: 6917
OvalAutos wrote:
Russell wrote:
Why was the car serviced evey 6K, that seems a little odd, or is it just that the car only cover 6K a year although that does not add up with the mileage and re-build info
It was the customer's choice to have an oil change every 6k miles. He was a bit worried because of the first failure (big end) and wanted a belt & braces plan.
I used to change mine every 6 months irrespective of mileage as a belts and braces plan - seems more of a placebo now.Now Golf GTI PP, 7 speed DSG.
Ex D3 and D4
28th Mar 2019 10:13 am
lynalldiscovery
Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274
Many moons ago vovlo fl10 crankshafts would not take a grind, grind and refit to a rebuilt engine and the clock would be ticking on how long before it broke, it normally wasnt long, after a few they finally listened and bought new cranks.
28th Mar 2019 1:33 pm
Kevo83
Member Since: 16 Jan 2018
Location: Wolverhampton
Posts: 35
adam wrote:
OvalAutos wrote:
Russell wrote:
Why was the car serviced evey 6K, that seems a little odd, or is it just that the car only cover 6K a year although that does not add up with the mileage and re-build info
It was the customer's choice to have an oil change every 6k miles. He was a bit worried because of the first failure (big end) and wanted a belt & braces plan.
I used to change mine every 6 months irrespective of mileage as a belts and braces plan - seems more of a placebo now.
same here every 6 months oil and filter change, booked in with oval auto on Friday for service
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can happen at any time.
