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Bang after 102 days

Fitting the clip to a gudeon pin .. An audible click should be heard to confirm the clip is in place .. wtf .. thats the instructions .. how do you know its in place .. if it goes for over 50 miles without letting go then its ok !!

Ive tryed mirrors and all sorts to confirm it .. hate engine rebuilds .. sigh

Sorry .. a little rant .. some instructions are kinda a waste .

Con rod appears to have ripped out of the piston .. small end failure .. cant say why though .. not sure about a clip failure to locate but ive not seen this before so i dont know .. building error or as GT4 says a mix of old and new components .. no idear im afraid .

Just my 2 pennys worth to a sad post .

I am sorry that it has happened though .. i wouldnt wish this on anyone :(
 
Demort said:
Ive tryed mirrors and all sorts to confirm it .. hate engine rebuilds

This is my favorite bit of an M96 rebuild, it's like playing operation or Russian Roulette.

I use a long mirror and quadruple check before passing it as done and I've never had an issue so far, you really have to make sure the end of the clip where it is bent sits in the little notch in the piston, if it doesn't most of the circlip could stay in place for a little while in it before it actually slips and the gudgeon starts to slide out and catch the bottom of the bore, then all hell breaks loose. I'm sure this is what has happened here as the gudgeon has been torn through the soft metal of the piston the same side as the bores are knackered.

This is how much you can see with the inspection mirror from one of my rebuilds, not a lot.

 
Chris I'm 100% with what you have said having looked at the video which shows the liners for 4-5-6 haven't budged (even after all this trauma). This has to be a circlip issue and a wayward gudgeon that's caused an instant jam.

If the rod had simply broken through use and fatigue the section making up the little end would still be intact and attached to the piston and the damage would also be localised to that cylinder.

Dreadful, my fingers crossed that the specialists involved can work something out for you.
 
scarletboarder said:
Thanks for the comments. I bought the car from a dealer. The engine was rebuilt on 24/11/15, details below. It has done approximately 4000 miles since with about 2k during my ownership. I've run it on 2 500+ mile trips and had an oil service on it as soon as I took ownership back at the rebuild garage for them to check everything was ok.
At the time I was accelerating up past 60 miles an hour at about 4500 rpm. Oil seemed to be coming from the left side of the engine underneath. No strange noises or issues prior to this.
0619b04d-4e31-47fe-b60b-d839f61467d2_zpsosyfozlt.jpg

06CE93D4-63B5-433B-8359-A890DB27A553_zpscwnrgj2a.jpg


Thanks, Phil W

Just read this thread, it's bad luck, but the good news is the law is on your side as of 1st October 2015 in the form of used car sales and the Consumer Rights Act 2015.

Get the vehicle data memory printed out to show you've not thrashed the living daylights out of it & you're 80% there to give it back to the dealer.

Which or Auto-Trader or .GOV or a phone call to the Free Citizens Advice Number will have lots of very informative direction of the new law passed in 2015.

It hopefully will come to your rescue :thumb:

All the best :thumb:
 
I'd be very confident that is a wrist pin retaining failure on the induction or more likely compression stroke.

The tell is there is one little end boss on the piston still mostly complete and one ripped to pieces with the piston inverted in the bore. The failure mode with the pin walking is it eventually binds on the bore on the end it is walking out of the rod/little end boss at and imparts a pivoting force into the little end boss on that end - essentially the crank is not going to stop so the rod is loaded in tension with the wrist pin now off centre in the little end bores and one end of the pin bound against the bore resulting in catastrophic failure of the little end boss on the opposite side of the piston. At this point the wrist pin is usually partially pulled back from the side of the bore it has bound on and walks the other way pulling the pin from the remaining little end bore and quite often flipping the piston over in the bore as it does so and smashing the skirt/bore etc.

Failure on the compression or exhaust stroke is more rare and generally shows as massive damage to the piston crown as well as the skirt and little end boss or a totally shattered piston where the little end and the pin has made it around once more and hit what is left of the piston on the way back up.

Sometimes in engines without centre support of the liner the liner fails first and allows the piston to carry on for half a cycle until the pin picks up on the damage to the liner and the above happens much the same way. Really occasionally the liner catastrophically fails but the piston and rod assembly stay complete.

You can confirm this quite easily by looking at what is left of the bore on the failed cylinder, if there are two horizontal deep scores/gouges running up the length of the bore or one thick horizontal deep score/gouge (depends on the bore diameter vs the finish and size of the wrist pin) then the failure was caused by the pin walking.

I've got a bit of experience of this failure mode as when I worked for someone else in a development role we experimented with press/interference fit wrist pins for reducing assembly weight..... it wasn't that successful :sad:

Happy to do you an engineers report if needs be and you can send me some pictures of the bore the failure occurred in.
 
scarletboarder said:
I'm in Stuttgart at the factory next Tuesday so will be taking along images etc just to see what they think.
Popping to the dealers with images in the morning. Not expecting a hearty welcome.

You probably know already but if you're a Porsche Club member and haven't been before, take your membership for free entry to the excellent museum.
 
CFo said:
scarletboarder said:
Popping to the dealers with images in the morning. Not expecting a hearty welcome.

I still think you should be looking at some legal advice regarding their responsibility.

Been to the dealers, business owner unavailable and no-one knows when he's back in, surprise , surprise. Left details of the failure and will be seeking out legal advice this afternoon.
 
poppopbangbang said:
I'd be very confident that is a wrist pin retaining failure on the induction or more likely compression stroke.

The tell is there is one little .....................

Happy to do you an engineers report if needs be and you can send me some pictures of the bore the failure occurred in.

Thanks for the offer :thumb:

05BE751E-5E4F-4983-87FC-594D2EFEFDEF_zpsrpqmire6.jpg

9EB389E4-7BA0-46B7-A36F-76E7B861EE42_zpsyrn3ar4h.jpg
 
I've attached a grab from your video to this post and boxed in red the two tell tale scores on the bore. You can tell even from the video that they are too deep and too straight to have been made post failure.

The rest of the damage followed this failure due to the unconnected rod flailing around and/or the liner failing either from the pin being pushed through it or the rod smashing it.

Likely cause is wrist pin retaining clip incorrectly fitted or old clip reused and either a failure of the clip or insufficient tension to retain due to being used once already.
 

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poppopbangbang said:
I've attached a grab from your video to this post and boxed in red the two tell tale scores on the bore. You can tell even from the video that they are too deep and too straight to have been made post failure.

The rest of the damage followed this failure due to the unconnected rod flailing around and/or the liner failing either from the pin being pushed through it or the rod smashing it.

Likely cause is wrist pin retaining clip incorrectly fitted or old clip reused and either a failure of the clip or insufficient tension to retain due to being used once already.

I've made some close ups from the photos I've got. The best are below.

23081121-7463-4603-B323-9A9AA713248E_zpspjaodwpc.jpg

6D27F9A9-1E27-407C-ACE7-94DD47C90DE9_zpssone1maz.jpg

D1E2689C-BB7F-410E-9237-CEF24117C913_zpsyrsmpjmf.jpg
 
Some extra data on the car/failure.
I was doing about 60mph at around 4-5000 rpm. The car was in auto and I did not change down at the time of failure. The car traveled for about 40 metres before stopping and was still in auto.
Engine rebuild done at 103071 miles.
The car was returned to the re-builder at 105476m where it was advised that an oil change and interim service was performed. No details were given of what was checked.
The car failed at 107630m
 
What did the dealers say when you popped in, OP? Edit - I've just seen that the owner wasn't available(probably hiding under his desk)

If it had been you who'd had the rebuild done I think it would be an open and shut case; you would have got something that wasn't fit for purpose and your legal relationship would be with the rebuilder under contract law.

I'm assuming a previous owner had the rebuild done, and then sold the car to the dealer? You might try to argue that the rebuilder owed future owners of the car a duty of care should they suffer foreseeable loss due the rebuilder's negligence, but I think that would be a hard one to stand up.

Legally it's much more straightforward if you can rely on contract law, so your most likely remedy is against the supplying dealer. If by any chance it was the dealer who had the rebuild done, then the dealer could claim for his loss in compensating you from the rebuilder.
 
I think the reason for the catastrophe is clear regarding the clip but why it took so long for it to fail is a mystery, I could understand 50-200 miles before it went walkabout but not sure why it would last a few thousand miles unless the clip simply failed or was misaligned but still held in somewhat, there isn't really that much sideways pressure on the clip.

I have fitted new clips and also re-used clips as there is no strain on them at all when installing and could be fitted a ton of times before any fatigue would occur. I just think the clip was misaligned on install and has took this long to shift.

See the picture below of how the clip should fit into the groove and the tab part into the space on the piston. If this wasn't aligned it may last all the miles it did but will eventually fail in the end. The clip tab could sit a few degrees off and not dislodge for some miles.


 
CFo said:
What did the dealers say when you popped in, OP? Edit - I've just seen that the owner wasn't available(probably hiding under his desk)

If it had been you who'd had the rebuild done I think it would be an open and shut case; you would have got something that wasn't fit for purpose and your legal relationship would be with the rebuilder under contract law.

I'm assuming a previous owner had the rebuild done, and then sold the car to the dealer? You might try to argue that the rebuilder owed future owners of the car a duty of care should they suffer foreseeable loss due the rebuilder's negligence, but I think that would be a hard one to stand up.

Legally it's much more straightforward if you can rely on contract law, so your most likely remedy is against the supplying dealer. If by any chance it was the dealer who had the rebuild done, then the dealer could claim for his loss in compensating you from the rebuilder.

The dealer had the rebuild done.
 

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