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YOUR RESEARCHNoticed a rod knock noise in my car...
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Install on a bench grinder and all
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Run them through a wirewheel installed on a bench grinder and all that carbon will come off.
Leading evidence: 'Install on a bench grinder and all' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check filter housing oil and filter' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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I did an oil analysis in November when I last changed the oil.
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I used an even cheaper one from EBay USA(ex China) to check wrist pin circlip insertion.
Use long-screw-driver-as-a-stethoscope method and listened all over
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I used the old long-screw-driver-as-a-stethoscope method and listened all over.
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Suggestion
Thus checking the filter housing oil and filter for scary metal debris is a good step.
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Suggestion
If you can jack up the car, poke around with a mechanic's stethoscope, check the oil filter and magnetic drain plug (if you use one) for debris and glitter, that should give you a pretty good idea.
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Suggestion
Resurrecting an engine after this failure is possible, with positive results, IF you take everything to the point of overkill with cleaning, flushing and servicing the engine afterward.
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Well, during the last 2 or 3 engine starts I've noticed a some oil smoke - which was never there before. And today I had to back the car out of the garage and while it was idling in the driveway, I noticed a distinct knocking sound...
The poor engine might not be much longer for this life. However, I've had the car nearly 8 trouble-free years and 55k miles. It's a '99 C4.
We'll see what happens, and I'll keep everyone updated.
I was just looking on ebay, and there are 3.4 liter Boxster engines in the $4-5k range... Any reason why that wouldn't be a "bolt-in" - accounting for the accessories and intake plumbing?
Just guessing but putting the engine in the middle of the car vs hanging out the back might create many different issues. Exhaust, motor mounts, transmission placement, coolant system, I think looking for a 911 transplant would be more efficient.
Jake, can you elaborate on what you mean by driving in cold temperatures? Are you referring to cold starts or even driving in cold temperatures even after a warm start? I assume your point is bore scoring and how cold temperatures impact it... What is 'cold' in your textbook and what advice would you give to people who drive their cars year round in 4-season climates?
Thanks
Indeed - lots of times... What's your theory?
Yes, of course - that's what I mean by "accessories". I mean, is the basic long-block the same from an M96 Boxster as an M96 996. Clearly, if I take the engine out of my 911, I have the exhaust, intake, engine mounts, etc. ready to bolt onto a new donor.
From the pic, is your car showing a little over 169k miles with original engine?
Jake is asking because these engines typically will score bores more frequently if driven in the cold, well cold startup that is.
Was your car sitting up for a while? It could be a lifter as well instead of a scored bore.
Mike
The engine was replace right before I got the car at 105k - so this engine has about 65k.
It doesn't sit much - I drive it at least every other day... but that does include some super cold weather.
Usually a lifter is more of a "tick" noise, but this is definitely more of a "knock" noise... Oil pressure is still good; coolant temp is good; it's running well otherwise... But something is amiss, I can just tell.
Good to know!
Rod knocking is rare. Before you blame a rod for the noise and condemn the engine be sure a water pump isn't failing.
Or with my Boxster a converter brick was loose. It would generate a deep bass knock upon cold start. Warmed up the thing would buzz like a heat shield was loose.
Once warmed up I can even hear what sounds like rod knocking from my Turbo. Turns out the noise is from the gear box, the rattle of the gears on the input shaft. When I depress the clutch pedal the noise goes away.
For this diagnostic task an electronic "Engine Ear" is useful.
Do not drive start the car unless for diagnostics.If your 'rod knock' damages the crankshaft .............
Drop the pan/dissect the filter.
BTW, another common source of knocking noise is a loose spark plug. Hope it's just that simple
Easiest is to use a mechanics stethoscope to poke around for the source of the noise (wear protective goggles and be careful poking around the rotating parts though).
Hey Van! Hope this turns out be something better than what you think. Hope you get it sorted out.
As a side note.....funny how the newbies think you're a newbie....
Might mention if a knocking rod is suspected an oil analysis might be called for. If it finds bearing metal in the oil analysis this could very well point to a possible loose rod bearing. If the analysis comes back ok this could let the rod bearing off the hook.
I am not afraid to spend a little bit of money to bring the possible cause of the noise into clearer focus. It is obvious, but it bears stating nonetheless, one doesn't want to drop an engine and split the cases to replace a rod bearing if the noise is from something else and outside the engine.
I did an oil analysis in November when I last changed the oil. Everything looks pretty good, aluminum and iron went up a little bit (cylinder walls?), but bearing material has been very low.
Also a good idea!
If you can jack up the car, poke around with a mechanic's stethoscope, check the oil filter and magnetic drain plug (if you use one) for debris and glitter, that should give you a pretty good idea.
I have a new clue - and I don't think it's as "catastrophic" as I initially thought.
I just got home from work, and when I pulled in the garage, I opened the car windows and let it idle - there's the knock-knock-knock noise... But when I increase the revs, the knock goes away - as opposed to getting faster. It's not there at 2k RPM, nor at 3k RPM, nor 4K. It's also not there when you blip the throttle.
So I'm thinking it might just be something loose in the exhaust system... I have another car on my lift right now, but I'll try to get it off this weekend and get the 996 up in the air.
I had thought I had the same issue. I heard a death rattle coming from the bottom of the motor while idling and thought I had spun a rod bearing. Flat-bedded the car 150 miles home to my tech. He heard it but wasn't exactly sure until he drilled a cat and shoved a rod into the element. The rod made the knock stop. whew. Bad cat.
Pull the sump. Move each cylinder to TDC and then sneak a bore scope into the back of each cylinder, accessing through the sump. See what you find.
This week has been cylinder failures left and right. We are at 11 cylinder failure calls from 996/997 and Cayenne on the week. ALL of them were recently driven in cold.
But of course, I have no freaking idea what I am talking about.
From page 1:
Jake, can you elaborate on what you mean by driving in cold temperatures? Are you referring to cold starts or even driving in cold temperatures even after a warm start? I assume your point is bore scoring and how cold temperatures impact it... What is 'cold' in your textbook and what advice would you give to people who drive their cars year round in 4-season climates?
Thanks
Well... the prognosis is not good. I used the old long-screw-driver-as-a-stethoscope method and listened all over. The noise is loudest at the front-end of the passenger-side valve cover. It does seem to lessen in intensity when the revs are brought up (even a little bit, like to 1,200-1,500 RPM).
Could it be the timing chain slapping around in there due to a failed tensioner ramp?
Knocking noise in 996 engine - YouTube
(Touching my phone to the screwdriver helped amplify it, too!)
Listen under the cylinder, just where the head meets the block. If the noise is louder there, than the cam cover, you have lost a cylinder.
If it's louder at the cam cover, you have lost a cam/ lifter.
Pull the filter and drop the sump, see what debris you find and if it's ferrous or not. Report back.
It was definitely louder at the cam cover, as opposed to the base of the head or the block. In fact, I was impressed how well I could pinpoint it with the screwdriver-to-the-ear!
When I get to play in the oil, I'll report my findings.
After listening to the clip and reading your posts afterwards then I would have say the noise is lifter or cam related.
This is not the end of the world.
However, I would advise you to avoid any more running of the engine.
You need to be sure the engine is worth working on. It probably is as the engine would have grenaded long before now with you continuing to run the engine with this noise present.
But it never hurts to double check as JR has stated many times. Thus checking the filter housing oil and filter for scary metal debris is a good step. In this case I would not be against dropping the oil sump plate but I have to remind you there can be stuff there that was there long before this problem appeared and which then could have no bearing on this problem.
If the cam lobes are fine you are probably looking at new lifters at least for the noisy cylinder. Porsche recommends if one finds say one bad intake lifter at a cylinder to replace all on that bank. The concern is I believe that dirt has gotten into at least one lifter and caused the problem and then all lifters are suspect. The lifter body tends to act like a little dirt/debris trap. Even if the build up isn't bad enough (yet) a possible concern is if this accumulation of dirt/debris gets disturbed it can affect another lifter. And then one is back in the engine, at least under the same cam shaft cover to replace yet another lifter. This gets expensive quick.
Check the sump too.. Always go straight to the sump! Remember, for debris to make it into the filter it must first pass through the oil pump. At minimum, you'll have pump damage, and that damage usually hurts the body of the pump first, as it is soft.
I bet they aren't ok.. He should be hoping to find the smoking gun there, though. Nothing else it can be is as cheap or easy to fix.
So they can charge more for the repair. That said, IF I have one bad lifter, I replace them ALL on the entire engine. Under no circumstance will I leave one side together. Why? Because lifters are miniature oil filters and the debris from the bad one will clog the good ones, then they become bad, pick up lash, and fail too.
Thats the proper mindset. It doesn't have to be a dirty lifter to fail. Porsche goofed up the lobe taper on some cams, and that effects lifter rotation surface speed.
Because oil has one way in, and no way out. Horrible design.
And have each cam lobe measured, using a cam profiler/ cam Doctor.
Debris is ALWAYS my major concern. Once the engine is back together shorten the service intervals and run break in oil. Employ a spin on filter adaptor to get rid of the factory filter bypass, and employ a filter mag, with a magnetic drain plug. Resurrecting an engine after this failure is possible, with positive results, IF you take everything to the point of overkill with cleaning, flushing and servicing the engine afterward. I do my first oil change 5 minutes after the engine fires back up again!
If I had to guess, you'll find something similar to this. I know I'd be hoping to, if it were mine.
Thought the spin oil filter and magnetic drain plug etc was a good idea. Went to the LN site and ordered the bundle including the filter etc. Went to shipping as I'm in Australia and US$170.00 to post!!!! WTF!!!
I pulled the sump cover off last night (and the oil filter element).
Overall it seemed pretty clean - If you shined a light on the oil, it looked like there were some fine sparkly particles... I swirled a magnet in it and nothing was picked up. There really wasn't much other debris - some green rubber bits (o-ring), some dark brown bits (non-magnetic, possibly plastic?) and one little shiny flaky bit (non-magnetic).
My guess is I'm seeing no reason why the rest of the internals have been compromised. I will still be sending an oil sample out for analysis.
p.s. my engine number is M96/04AT66Y65519, which I think means it's from 2000.
Thats not good.. Its sounding more like a cylinder now. This is very hard to diagnose, and the sound will fool the best of us, even in where the sound seems to be the loudest.
Save the money on the analysis, those particles that can be seen with the naked eye won't even show up in the test.
Do you have a bore scope?
Thats often the case, but the material is usually lager than what I see in his pics.
A black light shows a ton of material in oil that you can't see any other way.. Direct sunlight does as well.
The fine, almost dust type material is often from worn cylinders/ pistons.
Don't know how effective based on the resolution but before I pass judgement, been meaning to try one of these. At worst it's a very cheap gamble and would probably be on par with one of those self contained $100 units...
Amazon
Amazon
I used an even cheaper one from EBay USA(ex China) to check wrist pin circlip insertion. Worked great on the end of some coat hanger wire- full color and brightnesss control - all on your laptop!
It's non-magnetic, so it's certainly not from something like the IMS bearing.
Are the cylinder walls steel liners or are they part of the case halves (nikasil?)?
Good luck Van, I hope it works out for you.
After listening to your video and reading your symptoms they are very similar to mine:
- Oil smoke on cold start after sitting overnight from left side (bank 2)
- Tapping sounds from the passenger side, bank 2 (rises with RPM though)
Mine has been through 3 Canadian winters before developing these symptoms (can get as low as -30C/-22f).
I had a bore scope done and unfortunately cylinders 4-6 are scored. Hopefully this is not the case for you.
I thought people would like an update. First, here's a video that shows the steps I took to take the engine out:
Porsche 996 Carrera engine removal - DIY - YouTube
And, I've started tearing it down... The only thing I've discovered so far are leaking exhaust valves in Cylinder #6.
Quick look inside Porsche 996 engine - YouTube
My exhaust valves looked like that when I first took the engine apart. Actually the exhaust valve seats were more carbonned up than yours. Run them through a wirewheel installed on a bench grinder and all that carbon will come off. Then you can check out the condition of the seat area. Mine cleaned up really nice and I think so will yours. Anything else but an wirewheel on a bench grinder didn't take the carbon on. You will have to put some force on the valves when pushing it against the wirewheel but the carbon will come off.
Great videos and explanation!! I would be interested to see that suspect cylinder piston moved down in its bore and see what the cylinder looks like. Good luck! Fantastic videos!
Tear down is interesting but what I am eager to see is all the measurements of the bores - ovality and taper .
I mention this because if the #6 injector tests O.K. perhaps the blackening is oil not fuel related? Let's hope it is just the injector.
Speaking of which there is a Bosch injector upgrade available - '4 hole' and these are not expensive as reconditioned items.If you have the old ones , why pay for cleaning them? Just a suggestion.
Cool race car! Best of luck with the engine as well. Before it goes back in woul dbe the perfect time for an exhaust
It's awesome that we have people like Jake Raby on this board, so much knowledge, what an asset!
@Van
what was the outcome of the engine inspection? Bore scoring? Your action? Some advice for other 996 and 997 owners experiencing similar issues? Thank you kindly!
Yes, this is an old thread... (and I do miss my 996)
Teardown inspection showed the cylinders were pretty badly scored up. My best guess is this was from extreme cold starts, since I was commuting in the car all year-round. The pistons would heat up faster than the case and the metal would expand to the point where it was an interference fit with the cylinders. I wasn't ready for the expense of an engine rebuild, so I sold the car as-is to someone who felt they could do it cheaper. I don't know what the final outcome was.
As much as I'd love another 996, I've had a job change and now work from home. I rarely drive anywhere - unless I go to the track, in which case I'm driving a truck and trailer!
So what are your lap times with the truck and trailer? And does it bother you the trailer can never seem to take first, despite almost identical lap times?
The cold start theory was one of the first we had, many moons ago.. What you have to understand is the underlying conditions that exacerbate the issues related to any adverse environment, including cold weather.
Cylinder finish is one of those conditions.
That was my guess too.... at least the primary cause. I think in some pics I've seen scoring on just one side of the cylinder. Not sure how that could happen...a distorted cylinder and piston growth maybe. my question to you though is.... How did you drive it? Did you baby it till it warmed up (small throttle openings and let it spin up) or did you extract torque right away?
At home, it would always be parked in the garage, so it would never get that cold. But I would have to leave it parked outside at work (2-days at a time) - it was not uncommon for me to have to do a cold start at zero degrees. I think the coldest I saw was -15. I would let it warm up a few minutes before driving, and I'd never go over 3k RPMs until the water temp was up to operating temperature. But in that extreme cold, I think the damage happens very quickly.
I never let mine warmup because I hear knocking and rattling when I do. If I drive off right away and keep revs between 2,000-2500, no knocking. Been this way for 4 years now.
That's pretty significant. I'm sure someone could do the math: start with a cold engine at -20C, if you know the thermal mass of the piston and the thermal mass of the case/coolant/oil and apply a 2000C temp in the cylinder to warm it up, how far apart do the thermal gradients get? My guess is you'll get the piston up to at least 30C before the case is up to -19C.
