911C2_JagSType

When my 964 had 180.000km, like a year ago, I had the engine open so they will fix anything that could be close to break and so avoiding major problems in the future. It was expensive but thought it was a good idea. It was done by a Porsche specialist in Madrid who is faily reconised and that worked in Porsche germany.

Just after that "rebuild" and after driving for a while some times when stopping at a traffic light or stop I would get no oil pressure for a 2 or 3 seconds and then it goes back again to normal pressure.

When normal driving oil pressure was perfect. I told the mechanic and he said that it must be the oil pressure sensor only... so we left
it... (mistake).

Then like a year later but very few kms (may be 2000 or 3000kms) when arriving to a stop and without downsifting or overreving the oil pressure drops again and I start hearing a strange noise in the engine, so I immediately stopped. It was running with the noise may be 3 or 4 seconds only.

Took the car to the mechanic and it was the shaft to the pump (or
intermediate shaft not sure how to call it in english) that broke. I
attach picture. Apparently there was no damage to rods, pistons,
etc... but he has changed all parts worn by not having oil (don't know the name in english) total invoice in parts more than 3000€ and labor 2000€!!!

Now the question is, why was I getting that oil pressure failure when getting to idle after driving? It started after the initial "rebuild" so has it been a failure from the mechanic?
Could that previous oil failures have caused the oil pump shaft to break?

Basically, did the mechanic do something wrong the first time that has caused the problem and the second "rebuild"?

I would really appreciate your help to have arguments to defend myself in case it has been a failure from the mechanic and at least negotiate on the labor...

Please help!

Thanks

Jorge.

911C2_JagSType

I attach picture of the broken pump shaft, as you can see there is a bit of metal missing (which luckly didn't create any damage around the engine).

911C2_JagSType

http://www.facebook.com/photo.php?pi...&id=1580792734

Geoffrey

I can't see your pictures. Was the oil pump installed as a new part, or was the old pump cleaned up and reinstalled? While you can disassemble the oil pump, there really isn't a rebuild process per se and good practices would have replaced the oil pump with a new one given the mileage your engine had. The installation in the engine consists of an intermediate shaft which runs off the crankshaft via a gear and turns the timing chains on one end and is splined on the other. A shaft connects between the intermediate shaft and the oil pump. It is held centered using a circlip on the intermediate shaft and on the oil pump input shaft. If the clips were misplaced, it could cause the shaft to slide back and forth on the oil pump. splines.

With an engine with that many miles, good practices would be to check the gears on the intermediate shaft and potentially replace the shaft and gears including the one on the crankshaft if wear was beyond specification.

Indycam

http://www.google.com/imgres?imgurl=...1t:429,r:1,s:0

#2 broke .
Just bad luck , imho .

"A shaft connects between the intermediate shaft and the oil pump. It is held centered using a circlip on the intermediate shaft and on the oil pump input shaft. If the clips were misplaced, it could cause the shaft to slide back and forth on the oil pump. splines."
That's the one , the clips look to be in place . The driven end of the part has come apart . Half of the splines are missing .

911C2_JagSType

Geoffrey, on the first rebuild i dont think they changed oil pump nor shaft, probably they should have done?

Indycam and Geoffrey, but why was i getting the oil pressure warning, as explained above, before the shaft failure? Was it related? Because the oil warning started after the first rebuild and so i suspect that the origin is something not correctly done in the first rebuild.

911C2_JagSType

Can't you see the picture on this link?
http://www.facebook.com/photo.php?pi...&id=1580792734

If you can't I'll upload it to another service.

More questions just in case someone can help me:

The oil pump drive shaft was not replaced on the first rebuild as far as I know. Should have he done it after 180.000km? is one of the things that are very recommended to change at those kms? what other things should be changed / checked at those kms?

So if the drive shaft was the original, could have he made a mistake when re-installing it on the first rebuild and could that be the cause for the oil pressure warnings that started just after the first rebuild and which happened when coming to a stop at idle after driving for some time?

I suspect that those warnings are the key to understand what happened afterwards. Could have been the drive shaft "misssing a tooth" or something similar that caused those initial warnings and that ended up with the shaft breaking?

On the other hand if the shaft broke because the pump seized, what
could have made the pump to seize which could be related to the first rebuild? Could the oil pressure warnings have been a indication that the pump was going to fail soon? and if they started just after the first rebuild, could they have done something wrong to the pump on it?

What else could have created those occasional oil pressure warnings at idle that lasted 2 or 3 seconds when the rest of the time the oil pressure was perfect?

Sorry if I ask too much but were I'm trying to get is:

1- Occasional oil pressure warnings when coming to idle started just after rebuild, so the rebuild caused them.
2- Those occasional oil pressure warnings was an indication that
something was going to break related to the oil system.
3- It broke either first the shaft and then the pump or the other way around, but as result of something wrong on the rebuild.

Do you agree? could it be different?

Is it possible to get a "good" 964 engine now? at what cost? It could have been better to just replace the engine if the cost of repair was 6000€?

Many thanks!

By the way, he has now installed a 964 turbo (930 I beleive) oil pump (and shaft I imagine) which he said is much stronger.

Geoffrey

The 930 oil pump housing is stronger than the 964 pump, however, the pump volumes are different. I generally replace with a 996 GT3 pump as it is currently the best production pump Porsche is offering and costs the same as the other pumps.

I'd want to see if the shaft failed because of the pump or if it was the cause.

Gregg-K

What a drag, Jorge!

It will be difficult to tell definitively which was the cause and which was the result, but to me it looks like the female spline in the coupling sleeve failed from fatigue ... possibly a latent crack which grew until a segment of the swaged/splined end fell out.

Makes sense too, that as the crack propagated, the joint weakened and the failure accelerated.

Of course, this doesn't explain why it happened right after the first rebuild, but it does explain the intermittent loss of pressure as the splines skipped from time to time.

It would be difuclut to prove whether the latent crack was evident when your mechanic did the first rebuild, or for that matter whether it would have been "fair" to expect him to examine the part for signs of fatigue. In a perfect world, he should have sent everything out for crack testing prior to reassembly, but I doubt you would have liked the cost.

... Gregg

911C2_JagSType

IiiThanks geoffrey and gregg.

Gregg, but why the intermitent loss of preasure was happening only some times when comming to a stop at idle and never on acceleration or downshift?

springer3

Intermittent loss of oil pressure makes me think there was something wrong with the oil pump - possibly a foreign object entered, or perhaps a part broke inside and jammed it. That would break the spline. If somehow the pump passed the jam, [U]and[U] the shaft had enough splines left to turn it for a while, your symptoms are explained. Eventually the damaged shaft broke, and that is when you suffered a complete loss of oil pressure.

The only way to tell for sure is to open up the old pump. If it has only normal wear, that is a fatigue failure of the drive shaft. If the pump has internal damage, the shaft was damaged by an overload, and failed later.

Since the event is associated with an overhaul, I suspect the pump is damaged by a stray part. Your engine is probably OK since you were vigilent and shut down before oil starvation damaged anything.

911C2_JagSType

By the way, I just remembered that when the engine was open I saw that the chain had scratched the engine case... could have that been source of the problem? Or could the chain have scratched the case as result of the drive shaft failing?

If the chain was scratching the case, I imagine that the metal shreddings would get into the pump which could make it to fail?

why was the chain scratching the case? A failure from the mechanic on the first rebuild? either from mounting it incorrectly tensioned or from failing to detected that it was stretched and out of tolerances?

what do you think?

Thanks,

Jorge.
PS: He has now changed the chains...

911C2_JagSType

More pictures just in case it helps