Engine failure - what is unrepairable

benfinlayson · 3 Nov 2017

Evening all.

My friend has a 996 c4 2000MY with c. 50K on the clock. It is currently being inspected by a garage due to sounding like a bucket of spanner's (but still runs I believe - not that he is running it).

Garage has said they think it is a crankshaft issue and likely to be a replacement engine needed. Can anyone tell me what damage might result from such a failure and if the engine could actually be re-built if you had the time, money and inclination? What would you most likely need to replace?

Is a replacement crankshaft easy to come by second hand? Would it likely have thrown the timing out?

If it turns out its the IMS - same question, what damage is it likely to have done and what would need to be replaced worst case?

Any advice appreciated as it could end up in my garage being a project car (still greasing over the sale of mine a couple of years ago)! :eh!:

C4-STORM · 4 Nov 2017

Sorry to hear this! Sounds fatal

I don't think 2nd hand crankshafts are easy to come by at all..

Job for a pro!

PeterS · 4 Nov 2017

benfinlayson said:
Is a replacement crankshaft easy to come by second hand? Would it likely have thrown the timing out?

If you are asking this question, its probabably best that you don't tackle the rebuild yourself.

Also 'Crankshaft issue' is a pretty vague diagnosis. Am I right in assuming it is not at a Porsche specialist?

kurlykris · 4 Nov 2017

I`m no expert benfinlayson, but I would have thought that if the engine still runs then it is not the IMS shaft/bearing, as that is usually instant catastrophic failure/pistons meeting valves/heads as the shaft is a tube and just bends and eats itself destroying everything in it`s path, causing piston/conrod failure and basically destroying the crank cases etc. I believe the crank can crack/snap at the gearbox end due to the overhang of the crank from the last main bearing, which would actually sound like a bag of spanners as the flywheel and clutch etc would be waggling around like there is no tomorrow, but the engine MAY be salvageable from this if there isn`t too much damage due to running it ( member infrasilver has had this problem and rebuilt his engine himself ).

Obviously the best course of action is an inspection at a reputable Porsche Indy and then possibly an engine out and strip to access the damage/problem and how it can be resolved, before ordering a new engine from Porsche :thumb:

It may be just a silly fault like crankshaft sensors or variocams, you need a Porsche expert to have a look at it and rotate the engine by hand before jumping the gun :grin:

Best of luck to your unlucky friend :thumb:

benfinlayson · 4 Nov 2017

I am not exactly sure where it is, somewhere on London but they are a Porsche specialist (or at least they claim to be) I believe. They have said so far (based on initial very quick look) that if it's terminal (which they think it is, then he is looking at £5k engine and £3k Labour. Obviously at £8k he is thinking what his options are.

I will post when I find out more. They haven't even dropped the oil yet!

kurlykris · 4 Nov 2017

benfinlayson said:
I am not exactly sure where it is, somewhere on London but they are a Porsche specialist (or at least they claim to be) I believe. They have said so far (based on initial very quick look) that if it's terminal (which they think it is, then he is looking at £5k engine and £3k Labour. Obviously at £8k he is thinking what his options are.

I will post when I find out more. They haven't even dropped the oil yet!

If it`s " Terminal " the £5K engine and £3K labour isn`t even going to scratch the surface I`m afraid, more like £12K if the engine is salvageable and rebuilt PROPERLY without a replacement, plus incidentals :judge:

infrasilver · 4 Nov 2017

Used crankshafts are like rocking horse **** but if this is the reason it needs a rebuild (not a replacement engine) it will need main bearings and a crankshaft, (plus everything else ie gaskets and seals) the crankshafts are hardened a little way into the surface but are not supposed to be able to be reground due to the hardening process. A replacement used engine is not a good idea as it's an unknown quantity and at a low 50k miles for his car I would definitely rebuild.

You can buy oversize crank bearings for some reason though and I think I heard of somewhere that can regrind the cranks but I have never heard of one being done successfully or what the process for hardening again is, if it is actually possible? If someone is able to regrind them they would make a mint as there are a lot that have/do/will need them.

You can buy a new crankshaft for around £3000 from Porsche and I would say another 2k would cover other parts, plus 3k labour, yep sounds about right but that all depends on other factors.

I had a snapped crankshaft, as KK mentions and that still ran fine with no noise (just lots of vibration) cost me around £3k for the total rebuild, obviously no labour costs (DIY) and a used crankshaft was £1000, I was lucky I had some good contacts.

If the bearings have worn it will be noisy, this issue is usually down to running too low on oil or long service intervals.

Keep us updated as there is a lot of knowledge on here.

benfinlayson · 4 Nov 2017

infrasilver said:
Used crankshafts are like rocking horse **** but if this is the reason it needs a rebuild (not a replacement engine) it will need main bearings and a crankshaft, (plus everything else ie gaskets and seals) the crankshafts are hardened a little way into the surface but are not supposed to be able to be reground due to the hardening process. A replacement used engine is not a good idea as it's an unknown quantity and at a low 50k miles for his car I would definitely rebuild.

You can buy oversize crank bearings for some reason though and I think I heard of somewhere that can regrind the cranks but I have never heard of one being done successfully or what the process for hardening again is, if it is actually possible? If someone is able to regrind them they would make a mint as there are a lot that have/do/will need them.

You can buy a new crankshaft for around £3000 from Porsche and I would say another 2k would cover other parts, plus 3k labour, yep sounds about right but that all depends on other factors.

I had a snapped crankshaft, as KK mentions and that still ran fine with no noise (just lots of vibration) cost me around £3k for the total rebuild, obviously no labour costs (DIY) and a used crankshaft was £1000, I was lucky I had some good contacts.

If the bearings have worn it will be noisy, this issue is usually down to running too low on oil or long service intervals.

Keep us updated as there is a lot of knowledge on here.

Thanks infrasilver - I will keep you all posted. I did see a used crank on eBay the other day for £1200 so they do come up every now and again I guess and if I were to take on the car (due to my friend not being in a position to fund a rebuild) I can wait and collect required parts as they come up.

Question - how did you know your used crank was a good one? Did you have to have it measured etc? Also - did you have to tear the engine down completely to discover the fact it had snapped?

chriscoates81 · 4 Nov 2017

Ouch, just had a look on design911 out of interest as to how much they are new. £2800 - 3300 depending on year of car. I reckon that must be the single most expensive part.

MisterCorn · 4 Nov 2017

chriscoates81 said:
Ouch, just had a look on design911 out of interest as to how much they are new. £2800 - 3300 depending on year of car. I reckon that must be the single most expensive part.

These might look like a bargain when they become NLA. Unless main bearings are changed in time these are going to be more and more in demand.

MC

kas750 · 4 Nov 2017

MisterCorn said:
chriscoates81 said:

Ouch, just had a look on design911 out of interest as to how much they are new. £2800 - 3300 depending on year of car. I reckon that must be the single most expensive part.

Click to expand...

These might look like a bargain when they become NLA.

That will never happen. :thumb:

ditchvisitor · 4 Nov 2017

I would suggest he takes it somewhere with an in depth knowledge of these engines, i.e. Hartech/9E etc. Someone who claims to be a Porsche specialist could easily mis diagnose the problem.

benfinlayson · 4 Nov 2017

I have suggested to him that if he does end up paying that kind of money that he gets it done at a well known specialist so that come resale (which he will probably have to do) it will fetch more.

Harv · 4 Nov 2017

Post up the findings once the specialist reports back.

If it's a failed bottom end then I believe there's the option with the 996 3.4 of using a boxster 2.7 or 3.2 crank.

As for what's unrepairable, unless one of the rods or pistons has broken up and punched a hole through the case then most of the existing unit should be usable. At the end of the day the level of rebuild will be dictated by how deep the owners pocket for the repair is, if you can do some of the work yourself it will vastly reduce costs (taking the engine out, removing all ancillary components to short block and doing the same after rebuild to re-install will save at least 1k).

Keep us posted

maldren · 5 Nov 2017

It's not usually mentioned here but I understand that Porsche do an exchange short motor at a reasonable cost. I would expect them to exchange a motor with a worn crank.....

Engine failure - what is unrepairable

benfinlayson

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