Are 996 motors disposable or rebuildable?

Are the 3.4 and 3.6L watercooled motors designed to be rebuilt or simply replaced if a cylinder is "dead"? I performed a compression test on my motor and 5 cylinders delivered about 250psi and the last cylinder averaged 40psi!!! I repeated the test with the same results. The bad cylinder is number 4. I would like to take the motor out and tear it down and rebuild it with new rings. I am targeting rings because the leak down test didn't show any problem with the valves but did show problems with the rings. Additionally I am getting tremendous amounts of oily smoke out of the air oil separator, exiting out of the hose that returns vapors back to the intake manifold. The hose resembles an old locomotive chugging away.

Are you burning/ loosing coolant?

No I am not loosing coolant and when I did the leak down test I checked the coolant resivour(sp?) for bubbles and did not get any bubbles during any of the cylinder checks. Therefore I have ruled out a head gasket leak. Any thought on taking the motor apart and replacing the rings?

It's hard to imagine a ring problem severe enough to reduce compression to only 40PSI that hasn't resulted in cylinder wall damage. I wouldn't depend on bubbles in the reservoir to indicate a cracked cylinder or head gasket failure. A better test would be one of the kits to check for the presence of combustion gases in the coolant.

Porsche does not sell parts to rebuild the 996 motor so in essence they are disposable. IIRC its cheaper to buy a reman 996 motor from Porsche than it is to rebuild a 993 or 964 motor.

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Not true. You can buy all of the parts for an engine rebuild (that I am aware of). It still may be more cost effective to buy a factory rebuilt motor with a warranty as most independent shops will 90 days (or less).

Now that the latest 996's are nearing the end of the original 4 year/50,000 mile warranty period, I wonder if they will make engine parts available. About 6 months ago, Porsche made replacement parts available for 996 transmissions.

if the mixture is lean you can easily burn a hole in the piston. do you have any A/F data? you can take it apart and change out the rings. i don't think it's commonplace stateside though. autofarm, out of the UK, do this kind of work.

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I know you can get cylinder head parts and gaskets etc but bottom end stuff is unavailable and Porsche is really reluctant to provide the needed parts for a complete rebuild. Once something goes wrong inside a cylinder its cheaper to buy a new motor than trying to rebuild one.

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More importantly, if you are in fact loosing coolant can you then tighten the coolant back up?

If you are sure the engine is toast you could drop the engine and dismantle it to see what the problem is and then try and source parts. The last article I read said that Porsche is not supplying parts. However, aftermarket piston mfg's such as JE may be. If you end up getting a reman I believe you have to supply your old engine as a core. I would check to see what the stipulations are around this. Some damage would disqualify the engine as a core and disassembly might too.

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Funny, they are all in my Jan 2008 price list. Please give me an example of an engine part you can not get.

Here in Europe there are rebuild services offered on EBay. They advertise a 3k euro fix for "water in the oil" and various other engine services. Even if Porsche is not offering - the parts are available somewhere...

The parts are all on the Pelican Parts site. Although when you add most parts to your cart a message tells you it is special order and extra shipping cost and delay might be incurred. However, I've seen that on some other (non-engine) parts they carry for the 996, so it may just be a function of where some infrequently-needed parts are warehoused these days (Germany vs US).

If you had only 40PSI, I dont think there is enough compression for the cylinder to fire. Does it miss on 1 cylinder? Second, how do you know it is ring related? Third, how do you know oily smoke is coming from the oil separator? Did you disconnect it from the intake?

Tippy, Yes I disconnected the vent line that goes to the intake manifold and the hose smokes like crazy. The smoke smells like burn oil and is dark blue. It doesn't smell or look like the light blue smoke you may see from a tail pipe at start up. This stuff is thick. Regarding the conclusion of rings. I am only guessing because the leakdown test pointed that way. the intake and exhaust valves seemed fine during that test as well as checking the coolant for head gasket trouble. Regarding a misfire, I can't tell. The motor has headers and straight pipes and is very loud and pops and spits alot. I don't have the experience to tell you if that is a misfire or just what it is suposed to sound like without cats or mufflers. Let me know if you have any other thoughts or suggestions. Thanks everyone.

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side) to develop a crack near the top of the cylinder which results in a coolant leak -- into the cylinder (and a cylinder low on compression and possibly failing a leak down test). If engine run much longer crack can grow until it circles around and then a piece of cylinder breaks free. When this happens piece falls into cylinder and almost certain and complete engine failure follows immediately thereafter. If not a 3.4l but a 3.6l, then nevermind. I've never heard of the 3.6l engine doing this. Is the compression test results valid? 40psi on one cylinder vs. 250psi for all the rest sounds serious. A cracked piston, holed piston, broken rings, burnt and I mean seriously burnt valve(s) one or more of these is almost certainly the case. I would think it would be better to simply drop the engine and start an engine teardown to determine what's wrong: The cylinder head of the bank with with the low cylinder would be where I'd begin and see what turns up unless turning engine removal you spot something that points you to another area. Once you know you can decide if a partial rebuild, complete rebuild, or engine replacement is in the cards for you. Running straight pipes with no remapping of the engine ECU may contribute to improper fueling and could contribute to the engine problems. After you get engine fixed/rebuild/replaced, unless you address this, you could face the same situation again. Sincerely, Macster.

So what was the out-come of this problem??

The problem continues...I really believe I have a bad ring based on all the test (compression, leak down, using a bore-a-scope and looking at the piston). I replaced the air oil separator and that seems to have stopped the massive oil discharge but the amount of smoke coming out of the AOS vent line is not right. I am researching pulling the motor and having the head on that bank pulled so that we can view the piston. We might be able to fix it if it's rings or piston. But don't think I would go through the trouble if it turns out to be cylinder wall damage. If that then new motor.

Just for my own info. What year is this car? and what is your mileage?

Did they rebuild your motor or is it disposed of ??

Any update?? Could they rebuild this engine?

Consistent popping to me sounds exhaust valve/vlavetrain related but the blue smoke.......hmmmm. Lots of oil burning coming from the cranckcase, sounds worse than a head gasket? I wonder if the sleeve slipped? If you had a borescope in there, you should be able to see if the cylinder wall is scraped up, and even if it is, you can resleeve the block. I would look again if you can and see if the sleeve is all the way to the deck of the block.

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cylinders is valid and you believe the cylinder's compression is that low due to bad rings (is an understatement) then seeing alot more smoke (blowby) from any engine crankcase connection is not unexpected. If just the rings/piston are bad you can replace the bad rings/piston and chances are the engine's not going to be any worse for the experience. If the cylinder has some scoring with new rings it might still be 'good' enough. Depends upon the location of the scoring and the severity. Even so, the engine may still be salvagable. 'course, the engine will have to be pulled and disassembled. Then the severity of the scoring can be ascertained. It is not unknown, at least used to be the case, to simply hone one cylinder oversized and order an oversized piston/ring set for that one cylinder and button every thing back up. 'course, it depends upon the scoring: A couple of thousandths of a inch ain't much to take a cylinder out to but 0.030" is going a bit far for just one cylinder. And you have to find a source for the one oversized piston/ring set. Some piston makers can make a whole set oversized by 0.0005" or 0.001" or even more but they may balk at just one. Another possible solution is to talke to Autofarm (in the UK) and see if they can help. Autofarm has a sleeve solution that allows an otherwise serviceable Porsche engine to be resleeved and fitted with new pistons/rings and made as good as new. Displacement increases are possible too, up to IIRC 4.0l with a 3.4L or 3.6L engine (though a stroker crank may be needed which can really drive the price up). And a new/used engine is also a possiblity. Sincerely, Macster.

I replaced my 3.4 L with 57K miles with Porsche Reman for $8500 engine and $1200 labor. I had significant oil in the coolant and after several inexpensive possible fixes had to do something. A 40 hour head gasket job still left me with a 2001 engine so I went new. I stayed with the 3.4L instead of going to the 3.6L which would require new wiring harness, ECU, and no core exchange. And the engine was actually brand new and not remanufactured.

To have rings fail on 1 cylinder IMO is pretty unlikely unless the ring gaps were too tight from the factory. Evidence of too tight of rings would be scoring on the cylinder walls under normal operation. If it were turbocharged/supercharged, ring failure would be more understandable. But, the root cause would of been crown failure due to detonation, then the ring not being supported (lack of ring land support) leading to failure. Been there done that a number of times. But the blowby sure does point to it, I just have a hard time thinking rings would just fail on 1 cylinder.........

Any news or update?