herman maire

I just missed out on a local 2003 C4 911 that was parted out due to a accident..... they sold the 3.6L engine for $3500 in perfect running condition. I would have bought it for a spare.

They still have the C4 6speed transmission available..... there asking $1500. I was thinking it would be a good spare at that price.

I again find it very hard to believe all 6 cylinders/rings are faulty. Maybe try a few oil changes with some straight BREAK IN oil. It might help your rings get a better seal. Again, its a long shout but you never know.....

http://royalpurple.com/breakin-oil.html

herman maire

I dont remember if you removed the pistons from the cylinders....

If you did, maybe the rings are possibly worn to cylinders that are not quite oval and the rings possibly rotated. If you keep driving it the rings could possibly wear and achieve a better seal .

I would give that break in oil a shot, do a full flush of the current oil . Again, its a long shot but.....

You may have already read up on the "break in " topic but if not http://www.ntnoa.org/enginebreakin.htm

logray

Thanks again everyone for the input.

Yes I'm pretty aware that re-ringing without cylinder treatment is not the smart thing to do. And I normally don't do things that aren't done smartly. I guess I was just venting.

All 6 cylinder ring seals are not faulty. Those in bank 1, cylinders 1-3 are most certainly faulty - in various stages of disfunction, perhaps #2 being the worst. In bank 2, cylinder 4 has some evidence of ring seal loss and very minute amounts of oil burnoff/soot (tiny compared to 1-3), whereas cylinders 5 and 6 do not show any evidence of ring seal loss.

After reading the break-in link you provided I'm not sure a 75,000 mile engine could achieve break in or better ring seal. It sounds like once the glazing happens, the only solution is to re-hone and re-ring. There's bound to be wear that no oil is going to help at 75,000 miles. I'm not much of a fan of mystery fluids, but certainly break in oil sounds more logical than slick 50, . Perhaps it might be worth a few compression points? All kidding aside I will certainly be using 30 wt. break in oil per F6I/LNE recommendations if I do the rebuild.

No, I did not open the engine case. Only the heads were removed.

...

Anyways, I think my head is dug out of the ground at this point and even though the poll in this thread says to keep driving it, the other half of me is really starting to look forward to a 3.4 -> 3.6 L upgrade. I just hope I won't regret this decision. Spending $10k on a $20k car. Of course it will be substantially upgraded when I'm finished. I'm sure I won't be regretting it when I'm smoking other newer 3.6L 996's out there in my 1999 car.

When I pulled out compression tester on the 8 year old Dodge and saw numbers in the high 180's, it really gave me some ammo for the rebuild.

What I've read is very consistent with ring wear. Good static motion leak down test numbers (7%), but poor compression numbers (moving test) = bad ring seal. That coupled with the recent valve job, knowledge about the cylinder ovality issue, and vacuum gauge readings leads me only to once place.

Backwards spending $10,000 on a $20,000 car Crazy land.

: bowdown::bigbye :

speed rII

Logray, at least you are not spending 3k usd and be right at the starting point

I hate to put my engine back to my car with out the mods that I was planning to in future.

I think that I must start building engines to other people again... Just to finance my 996 hobby

logray

True that speedr2... I'm going to find the money somewhere... and I think I know where!

Ubermensch

If you haven't already read it, I'd dig through Hartech's website and buyers guide. They claim they have a method for returning cylinders back to circular without sleeving. According to their guide it's an application of heat and pressure in two directions to reshape the cylinder. They then machine the casing outside the liner and fit a restraining ring to prevent future "ovaling". I have no idea what this costs or how effective it is, but it seems like it might be worth looking into.

-Shawn

logray

Thanks Shawn, yeah I did read about their methods and they are interesting. They claim to be able to overbore Lokasil and put in new pistons w/rings that are weight matched. And while it is a solution (patch) the finances for it don't seem to make sense from the USA as I'm not aware of anyone in the world except them that does that type of work and has that kind of expertise.

Shipping the cases alone to the UK will more than make up the difference than it would just cost for me to have it done the "right way" here in the good ol' US of A.

logray

Judging by the votes I am supposed to keep driving the car and forget about the oily soot and low compression numbers.

But what fun would that be when I could have some more horses under the hood?

Anyways, as insane as it may seem to spend $10,000 on a car worth $20,000 on a good day, I am about 90% certain I'm going to take the plunge for LNE's 3.6L re-bore and "finish" the engine rebuild. A lot of it depends on how much funds I can raise.

Unfortunately the old girl is going to have to chip in to make this possible, as is the rest of the community.

Up for sale soon are some valuable upgrades for YOUR Porsche, so I can upgrade mine. We all benefit in the end you see!

Depending on how much of this stuff goes will dictate the build quality and extra goodies I can pile on. Such as...

-R&R connecting rods
-Level 2 crankshaft balance
-LNE billet chain paddle
-LNE spin on oil filter
-Mr Raby's engine rebuild class or DVD

Although it looks like Mr. Raby's (unfinished???) rebuild DVD might not be avilable just yet and it looks like I already missed the boat this year for his engine class. Shucks.

450knotOffice

I keep seeing you say that you don't want to spend 10K on a 20K car. Why? Who cares what the car is "worth". Look at it this way - if you enjoy the car, and it's generally in good shape, then spend the 10K to get the engine rebuilt properly. The most expensive item on the car - any car - will be like new and will give you many more years of enjoyment. In the long run it will be less expensive than buying another car, and once again losing more money through depreciation. You won't be spending 40K on a new to you used 997, which itself will have a "used" engine. Instead, you'll spend 10K on a car that's very near the bottom of its depreciation curve and end up with a gem of an engine and a car that will give you many more years of enjoyment.

Look, cars are almost always money losers in the long run (unless you're talking about a true collectible, which almost no 911 is). Since this is a given, you will lose less money in the long run by repairing this car as needed and enjoying it for as long as possible, rather than roping yourself into another 40 to 50K car every few years, only to see each of those cars lose tens of thousands of dollars of resale value by the time you decide to sell and move on each time.

Enjoy the car for what it is and spend the money as needed to keep it in top shape, knowing full well that in the long run you will lose LESS money overall by doing this than by replacing the car every few years.

jsoderbe

Hi Logray,

I guess I am dumb as a nail, but I still dont get it; how can you have perfectly even leak down and compression numbers, and still be so completely sure oil gets through on just one bank?

When you compare with your dodge, doesnt the relative compression matter? I would find a local rennlist member, and offer him a free leak down and compression test on his 996 3.4, just to validate your equipment and your numbers.

Basically I have understood these engines to be two separate engines, that is joined through the cam timing. That mean they could act different, and need to be treated differently.

I cant recall if you have done any exhaust analysus? Have you ruled out that the sooting is fuel? Have you interchanged the Injectors? Can you switch the harness to the injectors to the other bank?

Looking at the numbers you present, at least I would never connect that to your major symptom, the sooting in one bank.

Could your problem be that one bank is way too lean?

I am just saying, make sure you find the problem BEFORE you dump 10 grand into it! Worst case is that you dump the money into it just to see it sooting again after 500 miles.

If you dont find the actual problem, I would go for a 5 k used engine, and sell your restored heads to me....:-)


Regards,

Johan

Johan

logray

Thanks for the words of advice, I'm already over it. The car will be mine forever since I'm 95% positive I'm going to do the rebuild. It's still quite an investment though. Hey I guess people pick up old cars all the time and pour money into them for restoration. Perhaps my 996 will be one of the only one left running on the road in 10 years because it's engine will be rock solid. I suppose my hesitation was whether it would be smart to ditch the car and use the money to get into a newer model. But like you said that car is also going to have a used engine and it's own fair share of issues, etc... I'm actually more of a new car type of person, but when I sat in my 996 4 years ago, it was a pretty magical moment, this is part of my decision for doing the rebuild.

Actually a correction, oil is also getting through the rings on bank 2 in cylinder 4, but nowhere near to the degree as bank 1.

Here is my evidence for ring seal loss, hopefully someone can validate this info as the correct diagnosis which I've compiled. If there are any other tests I can do sans tearing the engine apart (which may happen regardless), please let me know!

1.) Low compression numbers but good leak down numbers. Even though compression is consistent, it should be much higher than this. I believe the theory goes: if you have good leak down numbers coupled with the low compression it means the rings are shot. Compression is a moving test, so as the rings move with the piston any imprefections, wear, ovality, cylinder wall damage will show up in the compression test, but not the leak down test - because that is static. When performing the leak down test all of the leakage was through the crank case. With the oil filler tube opened, all of the air from the cylinders was leaking past the rings. I could not detect any leakage through the intake or exhaust. Also the poor compression numbers were validated as being very poor by Jake earlier in this post. About three years ago @ 40k miles using the same compression tester on the same engine I was seeing numbers in the 180's. But I too am a little curious why would I see similar compression numbers, but different amounts of oil leaking past different cylinders. By visual inspection, in some cases, no apparent contamination, and in others plenty of soot. Perhaps the rings were never seated properly and the engine was not borken in as it should have been (I am the third owner). Or perhaps the engine was rebuilt at some point and the rings in bank 2 were replaced. I don't have a complete history from the PO.

2.) Low vacuum gauge readings. I've had a mechanic who works on 996's tell me the intake vacuum gauge readings should be above 18 inHG and between 18 and 22 inHG at idle for normal. Mine are barely 15 at idle. When blipping the throttle, the vacuum readings do not go above about 19/20. When they should go to 23-25 on a healthy engine. On my Ford, I see exactly this: 18 at idle, blipping to 25. So I know the gauges is working (yes it is not a comparative test though, I agree). The combination of the low gauge readings coupled with the low throttle blip reading indicates worn rings.


3.) Recent valve job. Many new valve guides, new valve stem seals, 3-way cuts, and vacuum/pressure test say that I shouldn't be having a problem with the heads at this point. This was partially confirmed by the leak down test. Before I spend all that money though and send the case halves off to LNE, I will certainly pull the heads first and do the solvent test to see if there is any leakage through the valves. If there is any evidence of a prolbem they will go right back to the shop. In fact I might bring the #1 head back to them anyways just to get their opinion on the data I've got. The valve job indicated there were problems in bank 1 such as several very bad guides and an exhaust header leak, so I am wondering if those problems could have perhaps accelerated or casued the increased ring wear or perhaps leakage/contamination problem. Those problems were not present in head #2, and there's not any soot there either (or at least a very very small amount in #4, not enough to make it all the way to the tail pipe). Still though, after the head work and valve job, if the source of the problem was with the head I should think it would have been resovled. So perhaps the damage was already done (rings) or there was an unrelated problem at the same time (rings or cylinder ovality).

4.) Presence of oil on spark plugs. The plugs, just after 500 miles (now 650) after the valve job are coated in what looks to be oil fouling.

All of bank 1 plugs look like this.



All of bank 2 plugs look like this.



5.) Presence of soot in the exhaust header and exhaust ports. Pulling the header reveals a lot of this soot - basically everything is coated in black, where it was basically clean upon installation, it looks like it's seen 50k more miles. If this were a diesel I wouldn't be concerned. Comparatively, bank 2's exhaust ports, plugs, and header is still relatively clean. Although I did detect a very small amount of soot in #4/bank 2. Certainly, carbon is a fact of life for any engine, but the soot, and non-scientifically leaves an oily residue when wiped with my finger, indicates contamination.

At this point based on the above info I am very confident it is ring seal loss. What else could it be??? Of course there are still many many other reasons for sooting.

Yes is absolutely does and you are 100% correct, this was more a sanity check to make sure the gauge was not stuck or something. It would be smart of me to do this.

I pondered that perhaps the cam timing could be too retarded, which could explain excessive oil consumption and sooting. I experimented with -6 degrees retarded, 0 degrees, and 6 degrees advanced. In the end of that test, the soot accumulated just as quickly in the tailpipe for bank 1 on all three cases. Within just a few short miles, the soot was back after cleaning the pipe. And in the end the engine runs the smoothest and has the most "butt dyno" power at 0 degrees camshaft deviation.

I have considered this and am not sure if I've ruled this out 100% yet. Perhaps I should also test for volume and pressure. I'm not sure how else to test this aside from taking Durametric readings related to fuel delivery. I had the injectors sent out to be cleaned and tested and they came back to me tested 100% and were reinstalled back in the engine in a random order. Here is the fuel injector report:

http://img851.imageshack.us/img851/3015/drinjector.jpg

The numbers provided from Durametric say everything is in spec:

FRA at 1.04 for both banks and TRA at -0.16 for both banks.



Additionally I replaced all of the oxygen sensors during the valve job rebuild. Same soot before/after rebuild.

Do you still feel the same way now after the above information? Are you thinking the oil contamination would be coming from the valve guides even though they were all measured and bad ones replaced, then valve stem seals replaced with brand new and the valves cut 3 ways, along with a good pressure/vacuum test? Or are you saying the AOS is dumping oil down the intake? Maybe the spark plugs aren't hot enough? This is also the third new AOS on the car, and the intake risers looked identical between the two banks when I last had them out. The brand new AOS appears to be fine BTW, I tested it with a slack tube manometer.


Both cats read 180 degrees F...

jsoderbe

Well, I'm not the one you have to convince, it is you that have to be convinced....

I'm just saying, you should be able to drive a car with that consistent leak down and compression numbers all day long. Sure you would miss some power, but it would still be a powerful and fun car to drive. Much as your seems to be today!

I would never pour 10 grand into the engine before I know what is wrong. I think the 3,6 route is the right desicion, and I think you will gain 5 k back in higher resale value. But, think of the absolute nightmare if it is still sooting after 100 hours of work and 10 k.

I guess it is another learning experience for me, but isn't the O2 values way off? If you replaced the sensors, did you re-check the values afterwards? If not, have you replaced the O2 sensor wiring?


Regards,

Johan

logray

You have a good point. I'm all ears, any ideas on where the oil or fuel contamination could be coming from? MAF would affect both banks. If it was an 02 sensor, I would see it in the readings. Besides the old 02 sensors I had on before the valve job gave me the same readings and same sooting, albeit they took longer to heat up.

The values are nearly spot on actually. The right two columns are supposed to fluctuate like that. I have the factory set points for 90deg C idle from the workshop manual.

Ign timing is supposed to be 5.3 +/-0.7. Mine jumps a little higher than that as does rough running, possibly from a slight miss due to fouling or combustion contamination or timing is not 100% dead on, or???

Air flow is supposed to be 17 kg/hr +/- 2.5. Spot on.

Short term fuel adaption FRA bank 1 is supposed to be 1.02 +/- 0.04 (mine's at 1.04 and steady)

Short term fuel adaption FRA bank 2 is supposed to be 1.03 +/- 0.05 (mine's at 1.04 and steady)

Long term fuel adaption TRA bank 1 & 2 is supposed to be 0.00 +/- 0.1 (mine is at -0.16 little out side of that)

O2 sensor voltage is supposed to fluctuate between 0.04 and .79... Durametric can't read that fast, but it does fluctuate like it is supposed to.

As for the wiring, if that were a problem I think it might show up in the sensor readings?

jsoderbe

Ok, that explains the jumping values. But, how can you rule out a intermittent wiring problem? Would the CEL catch that?

I'm not that familiar with the US terminology, but am I right when I don't see any exhaust related values in your documentation? Over here in Europe we measure the exhaust carbon oxide level (CO) and the amount of unburned oil related hydrocarbon (HC). Not sure what you measure in the US, and the terminology.

A typical CO value is 0,1%, and HC is maybe 20. A worn engine show a significant increase in both, which eventually will make the car fail the mandatory vehicle inspection. My 996 showed CO 0,00 % on both banks, and a HC reading of 0 and 3 respecively, showing a very, very slim difference in the amount of unburned gasoline and/or oil from one bank. The unburned gasoline and/or oil is what create the sooting.

I would anticipate that you have different values for each bank, and maybe these values might point you in the right direction?


Regards,

Johan

Reborn996

Logray, I am in San Jose and have a 2001 996 3.4 with 88k miles... willing to have testing done on my car with your tools if you want to do a comparison.

David