speed rII

Hi,

I posted this problem on the noise topic that I had.

So if some one knows that is this one of the weakparts of this engine, please chime in.

The cyl.5 rodbearing broke completely, and I cant figure why. All the other bearings were like new.
No overrevs in ecu memory, nothing unusual.

If the services would have been neglegted, there would have been wear on all bearings???
Like I mentioned, the rest of the engine is like new with just litle wear marks here and there.

If enyone have good theory, or knows what I must do to prevent this in future, share your thought's

logray

I wonder if a variocam pad became worn enough that pieces of it (or any of the other plastic parts in the engine) got into the oil passageway for that bearing.

Was there always sufficient oil in the engine? Perhaps a previous owner let the oil level get too low?

With any luck rebuild the bearing carrier, case, and you'll be back on the road.

Does it look like there was any other damage? Did the engine seize/other damage or was it still running when you pulled it apart?

This is one of the reasons why I think any owner of the M96-01 should regularly change their cam pads... here were mine after 75k. AND there were certainly bits of this pad in the oil sump, perhaps elsewhere? Only a tear down might tell me...

ivangene

theory says an oil feed passage got plugged....

from what?
a piece of silicone, a fleck of metal, a chunk of plastic, an o'ring or any other item thaat may have been floating around in the case from an earlier repair, factory blemish or wear and tear item...

just a thought

speed rII

Thanks, all the oil that goes to the crankcradle, goes thru the oilfilter first. Only thing that is in clean pressure side is the oil cooler, hmm....

Took the crankcradle apart today, and the mainbearing that is on the same oilcircuit with the 5 rod, was allso wery poor condition. So oilcirculation has been compromised at some point of the cars history.
I have no service records from the car, so I have no idea what the previous owner has done. All I know is that I'm second owner. Yep, stupid me, never buy a p-car with out recorded history...

I think that I chance the oil cooler allso.

Found the conrod from england, and local machineshop will repair the crank, if it's repairable.

logray

If I'm not mistaken, the oil filter system in this car is not a 100% inline filter, meaning it only filters a portion of the oil at a time, so over time it will filter all the oil, but not all of the oil must pass through the filter before being distributed to the engine.

This design may have aided the possibility that perhaps a passageway became clogged by excess sealant that broke lose or plastic (from wear parts) that did not make it's way to the filter first.

Macster

That just one bearing showed signs of wear pretty much eliminates neglected services or the wrong oil.

Without being at the engine to confirm the oil feed to that bearing and other bearings I can only offer the theory that the oil passage to that bearing may have a leak and thus delivered less oil.

The oil passages are cast in and when the engine assembled sealant is used to seal the passages. However, a manufacturing defect can have one of these passages leak and of course since it is an internal leak there's no oil on the outside of the engine but pressure and supply are bled away.

Also, I'm not sure how to check this but you should try to confirm the oil relief valve that controls oil to the piston jets is working properly.

This valve is there to if the oil pressure drops below a certain pressure the oil to the piston jets is cut off to reserve more oil and oil pressure for the main/rod bearings.

Sincerely,

Macster.

speed rII

Thanks guys,

Logray, I will check that oilsystem. I'm quite sure that all the oil goes to the oilfilter first, then cooler and so on.

Macster, the oiljets might be the cause. Will check those before I put the engine backtogether.

logray

I can't remember where else I read this but here is one source:

From http://www.lnengineering.com/oil.html

"Most stock engines have a spin on or cartridge style oil filter. In the majority of those cases, it's a bypass filter, where only a small portion of the oil actually goes through the filter. It's the idea that the oil is constantly filtering, so eventually all the oil will get filtered.

With full flow filtration, 100% of the oil goes through the filter. This does however require very high quality filters with HIGH burst strengths and durable construction, especially of the internal filtration media, because what's the point of full filtration if the media just bursts and lets the contaminants out and doesn't filter the oil?"

Edit: ah yes here it is:

http://www.lnengineering.com/spinonfilteradapter.html

"The LN Engineering Spin-On Oil filter adapter also helps improve the longevity of your engine by providing full flow filtration, which means 100% of the oil gets filtered without having oil bypass the filter (as the factory filter housing allows for)."

RPMulli

Hey quick question.. is there a way to inspect the variocam pads? pull of the valve covers?

speed rII

Yes, you need to pull the valvecovers to check the variocampad's

Macster

The 993 (at least) came with 2 oil filters. The main engine oil filter and a smaller bypass filter intended to trap finer particles that Porsche feared could harm the zero-lash valve adjusters.

Over time I guess the concerns Porsche had regarding the zero-lash valve adjusters proved to be unfounded and the 2nd filter was done away with on the new water cooled engines.

AFAIK Porsche does not use a pressure bypass at the filter to route unfiltered out around the filter. Any overpressure is dealt with at the oil pump.

Sincerely,

Macster.

speed rII

And for the oiljet's. There was couple of jet's where the ballvent was completely open, so I'll bet that there is the reason.
Just added those in the parts list...

Logray, thanks looking the oilpassages in the block made me thought that all the oil would be filtered.
Now I'm sure that I need new cooler, the inside of the cooler is some wiremesh and if the debries got there there is no way to clean it.

So, if your variocam pads look like the ones in logray's pics, well mine did. Would it be best to tear down the whole engine???

logray

It also goes to say, because the cam pads and 4th and 5th chains of the M96-01 engine are so inexpensive, if you are going through the effort of pulling the covers off (which requires specialty tools), pulling the camshafts out to replace the pads and chains is not that much more work... of course you need to be comfortable with re-timing the engine (more special tools required).

The hardest part of the job is reinstalling the cam covers. The bead of silicone and tightening sequence of the cam cover requires precision and patience. Using too much silicone can create problems with oil passageways becoming blocked. Using too little or not in the right places can mean leaks and you will have to pull the cover off again to reapply. Doing it with the engine installed is not recommended if it is your first time, but it can be done, as I believe speed rII did by dropping his engine a few inches. I do not recommend doing this work without a copy of the work shop manual.

Also new micro-encapsulated cam cover bolts should be used if you don't clean and apply Loctite 5900 silicone on the base of the existing cover bolt heads.

logray

I know the recommendation is there for a blown water pump impeller for a complete tear down. Otherwise blocked cooling passage could lead to cracked aluminum. OF course, I don't know what is worse, a cracked engine or a spun rod bearing.

I am not sure about the recommendation for excessively pitted pads or excessive silicone. If so, I need to get my engine back on the stand right away. Of course, it might get torn down anyways due to low compression and worn rings/soot. But I won't know more about that until I've had a time to re-test those things with better tools some time in a few weeks.

Not the same noise that you had, but I have a slight ticking on cold startup that goes away after a few seconds, which I believe could be either normal tensioners filling with oil/chain slap, or abnormal oil passageway blockage, or excessive leak down past the rings (or perhaps even valve seals/guides despite valve job) causing slight oil burn off on start-up.

logray

At the expense you are already undertaking by tearing the engine down, add another oil cooler to your list, it is a very small fraction of your total spend at this point. It's not worth the risk, although I am not certain of the design whether it would allow for such particles to become lodged in and possibly freed at a later time. Still though, for the cost and potential for intermix failure down the road, I would personally replace it.