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YOUR RESEARCHdead motor
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Replace last year is now sans the impeller blades(?!)
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Performed · outcome unconfirmed · Original poster
The water pump that I replaced LAST year is now sans the impeller blades(?!).
Leading evidence: 'Replace last year is now sans the impeller blades(?!)' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check pistons closely' (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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Performed · outcome unconfirmed · Original poster
I used a few references to get the different specs, etc.
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Performed · outcome unconfirmed
I have exceptionally good used pistons for sale, we never reuse them and generally just throw them away.
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Performed · outcome unconfirmed · Original poster
All 6 pistons are marked by the valves, so I'll contact you via phone next week in re: used serviceable pistons-along with another IMS.
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Performed · outcome unconfirmed
The last time I had a snapped camshaft was in a BMW I bought used when a previous owner or some one that worked on the car forgot to torque the cam holders to spec.
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99 996 with 109k. Engine died at idle, wouldn't start again. Turns over such that the motor is having valve interference issues. No oil under the car at all.
Oil pressure at idle was running fairly low, with the dreaded white smoke cloud at high rpm.
My conclusion: timing chain tensioner dropped, allowing one chain to skip a tooth. Since this is a fairly high milage motor, with low oil pressure, I'm going to overhaul it.
My question: As an aircraft mechanic, I think that the in house overhaul would be the best, most cost effective way. Since I've not overhauled one of these before, any suggestions? I'm looking for a good source of the parts, services, and materials needed. Also, any recommendations for a rebuilder in the SE US? (Just in case)....
Thanks
Kbollaert, welcome and I see you are a paying member. Thats the first step.
Its probably no more complicated than any other engine you have worked on. At a minumum, get the Bentley manual, read all engine posts here and Renntech.org (also become member there). If you have many $$$ in tools (which Im sure you do), and a good work area, you will be fine. Its obvious just from your post, a teardown/inspection is needed.
Read and study everything you can find on the engine and how it works then the light bulb will go off. I am not a pro-mechanic but have an extensive mechanical background. I am confident I can do anything on my engine short of actual machine shop work.
Listen to the experienced guys here, laugh at the ribs and jokes, then DONT GET IN A HURRY!
Oh and I almost forgot. You MUST post some pics or no one is allowed to help you. (1st joke) but please do post pic.
You should consider talking to this fella about his Duremetric cable as long as it has at least one vin left. Enthusiast cables will do 3 then I think Durametric will let you buy more.
https://rennlist.com/forums/996-foru...-for-sale.html
http://www.durametric.com/default.aspx
Your white smoke may have been a bad AOS or cracked head.
As far as stock parts most on the board would probably use Sunset Porsche or Suncoast Porsche. They give a very good discount.
Jake Raby Flat 6 (
http://www.flat6innovations.com/
) and
LNEngineering (
http://www.lnengineering.com/
)
Are two that have modified and re-engineered parts that have shown weaknesses
Hartek in UK has also written extensively about these engines.
There are a couple of folks on this board that have documented partial and complete rebuilds.
Logray is one
https://rennlist.com/forums/996-foru...he-finale.html
Dharn55 was one of the first to repair a cracked head.
https://rennlist.com/forums/996-foru...-repair-2.html
Pelican parts had all the parts for my 996 project. Mine had a jumped timing chain and some bent valves. Did all tge reapirs alone, in my two car garage, using home made locking tools. Have a complete write up on the Canadian forum. Look under "Dragged me home one of these".
Sorry to hear about your situation. The Bentley manual is good but doesn't have full engine building info - you'll need the CD manual that you can find online. You'll also need a few specialty tools, (or fabricate them) depending how deep you go. Look for logray's rebuild here on Rennlist as fpb111 says - a great resource with lots of pics and info. The big thing with these engines is the proper assembly sequence - other than that, it's just an engine. I think with your aircraft background you are probably going to be fine. Take your time and take lots of pictures to help you re-assemble. Lots of suggestions on this forum for parts suppliers - I've found Pelican to be good. Good luck and let us know how it goes.
Very sorry to hear about your engine failure. If you are in need of assistance or interested of rebuilding your engine with high performance parts, we can gladly assist you.
Bisimoto Engineering carries an entire line of custom high performance forged aluminum pistons in which can be tailored to your choice of bore size and compression. Along with forged steel rods to handle greater cylinder pressures and rpm at very reasonable pricing. Kindly give us a call or email for additional information on all available Bisimoto products and services to get your vehicle up and running stronger than before!
- Julio A.
Update:
After tear down, I found the 1-3 intake cam broken between 1 and 2 lobes. Every valve was bent, but I didn't see any obvious cracks around the valve guides. The pistons were marked, but not enough to replace, unless I find damage when I dye-pen inspect them. The cylinders are not damaged, and seem to be in good shape. The crank seems to be in great shape, but I'm going to get it mangafluxed to be sure. The water pump that I replaced LAST year is now sans the impeller blades(?!). One of the chain guides is worn, but I'll replace all of them anyway. Overall, I'm pleased with the condition of this motor, even with the damage that it has. Pics will follow soon ( really!).
Wow, that's a new failure mode for me, a snapped camshaft. Curious your impeller blades are gone too.
I wonder if bits of your impeller blades got caught in the head passageways and caused an overheated condition? Heat might be a factor in low oil pressure. Lost plastic impellers have been attributed to cracked heads.
Or you skipped a tooth and bound a valve and sheared the cam as you thought.
Can you post a pic of the broken cam?
Sorry about your engine failure. It's good that you're an aircraft mechanic
Just wondering how long have the low oil-pressure and smoke issue persisted leading up to the failure?
With finding a snapped camshaft, did you notice if the cam holders or caps were torqued to the right specs?
I've had a broken camshaft before on a different car due to previous owner tinkering with the engine and not torquing everything down correctly.
Update: Just a few pictures showing the particular failure modes on this engine. I didn't bother with the rest of the pictures showing the removal and dismantling: who needs that after the great job the Logray did with his?
The most disturbing (annoying) is the $350.00 water pump that lasted around 18 months or so. I couldn't tell you where I bought the waterpump from: I believe it was from Pelican Parts, IIRC. The damage pattern looks like one vane gave away and took out the others. A serious system flush is in order here.
I also show the 1-3 intake cam where it broke.
The third picture shows how I held the variocam actuators closed using 0.032" safetywire.
On a side note: While I could have raised the rear of the car higher to clear the motor, I instead opted to remove the MAF and intake risers. This allowed me to keep the car on the jackstands without having to add wood blocks to the jack in order to get it high enough.
All of the bearing surfaces, crankshaft, camshafts (except the broken one), etc. are in very good condition. I'm now waiting for the heads, crank and rods to come back from the shops so I can proceed on to the next phase.
The last time I had a snapped camshaft was in a BMW I bought used when a previous owner or some one that worked on the car forgot to torque the cam holders to spec. One got loose and vibrating a few others loose. However this happened on Hollow camshaft. Until then, I never seen a backfire happen on the intake side(as oppose to the exhaust muffler) before.
I wonder if there was previous work with lifter replacement or anything of that sort?
I just spoke to the machine shop where I'm having my crank/rods magnafluxed and polished. He can't find the specs for the crankshaft journals. Anyone? Hello, PCNA? Hello?
In re: the questions about the broken cam:
the saddle brackets seemed to be torqued the same as the rest of the mounts, so no problem there. I looked at the break to see if a crack might have been preexisting, and propagated through the cam. Nothing as seen through a magnifier. As I recall, this cam was solid, but I'll check when I get back. There was no heat discoloration anywhere indicating an overheat condition. I'm going to have the cams magnafluxed anyway, just in case.
Yeah. It would be that easy, if you had not just one, but a few dozen to measure that were all new then they can all be averaged for a real number.
Thats one way I created my own, it just cost a ton of money in the process. Building Grand Am engines from brand new cores that were never ran outside the factory helped things quite a lot when gathering my data, at least for some of the different engines.
Anything I have had to work for years to acquire is secret, no free lunch here.
Surely the "new" cranks don't vary more than a few .0001's of an inch ( I refuse to use metrics unless I have to). I would think you could extrapolate the same information from enough used crankshafts.
LOL, I understand but ALL this info will be in your publications, right? Could you please type faster and get them out. Just kidding
.
(see Alp, I fixed it)
Unbelievable.
You do realize there is only "24" hours in a day, right.
What you're asking him is to forego daddy time so that he can please you and I don't think that is going to happen.
Jake has the option of being anti Burger King at this point with his data. "You can't have it your way" and you'll get it when you get it...
Its not about speed, its about accuracy and having the best illustrations and component drawings possible. I have been compiling the info specifically for the book for over 5 years already. Honestly, we learned so much in 2012 that incorporating the info into the book was critical and it was also a very time consuming addition.
Hey, I just like messin with ya, hence the wink. No need to get offended on anything I say. If I gotta problem with you, I'll just find out where you live and change your oil with M1 0w40 while you're sleeping.
I should have known. Chicago humor, right!
Seriously, I think whatever JR decides to publish will be a goldmine of 996 info and I look forward to paying the astronomical cost. Unless its cheaper to just buy a TT.
Engine overhaul checklist & parts spreadsheet. Please review and comment. I used a few references to get the different specs, etc. (Thanks Logray and Jake). I know that I've missed a few items, glossed over others, and probably have the sequence wrong in other areas. The price points quoted were Pelican Parts, for the most part.
Thanks for your input.
The water pump has a plastic impeller. Looking at it, I'm amazed that I didn't see really high water temps: that thing is destroyed! I can't tell who the manufacturer is, it just has the part number with no manufacturer data that I can see. The broken cam is indeed hollow, I'll post the pic later.
Not surprised.. The reason why the temps didn't elevate is because the coolant stopped flowing to the temp sensor. The position of the temp sensor in the system makes this worse.
This is a classic situation that can get much if not addressed thoroughly.
Picture 1: This is what happens when you don't use the best quality tools that you can get: you get to spend more to fix it!
2: broken (hollow) camshaft
3: ims bearing. Still turning, but with a little bit of roughness. 109k miles.
Caspar Labs tells me that they have sold around 75 or so of their ceramic bearings. I'm thinking of going with them. I'll post my results here.
scariest. picture. ever. There must have been a manufacturing flaw, the cams don't even look worn, how the heck did the shaft fail? Is there a busted sprocket or a snapped chain your not showing us? This picture is the stuff of nightmares ...
All 24 of them. I had to replace some of the guides also, due to bellmouthing/cracking. I had the machine shop replace them all. My guess is that the ims chain tensioner dropped, allowing that chain to skip a tooth: that's the only one that would do that much damage to both banks-unless I'm missing something.
Or MOF#24 which is a failed/ failing IMS assembly, not the bearing. Something similar to this:
You Tube
These can partially fail and the cams will remain connected, but the cam timing is retarded and will usually bend only exhaust valves.
With these failures you have to find the smoking gun, or you'll revisit the problem later. The tensioner paddle can be at fault, as well as its wear pad, that when worn enough can easily allow the timing chain that drives the IMS to "jump teeth", which usually happens at start up when the IMS tensioner is not pumped up.
I see cams fail quite frequently and they generally snap in half at that same point and its due to collateral damage from trauma elsewhere within the engine, like a valve colliding with a piston.
Check the pistons closely for crown and top ring land damage after they contacted the valves. I have exceptionally good used pistons for sale, we never reuse them and generally just throw them away.
Look over this entire engine with extreme attention to detail. I see some traits.
The manufacturer of that precision piece of (?) cutting edge engineering is:
Dr. Ing. h.c. F. Porsche AG.
Wow, you say to yourself, that's an impressive sounding name for a company that builds cars when compared to other car builders with names like Toyota, Ford, Chevy, or whatever. But what does it mean in English?
It means: Ferdinand Porsche, Honorary degree of doctor of engineering, Incorporated. Wait, you mean he has an honorary doctorate degree in engineering? So a university just gave him this fancy degree which he displays in a highly prominent position in the name of his company, even though he never formally studied engineering and graduated? Hmmm.
Oh, I get it now! Porsche was able to learn his trade by practicing on his customers through trial and error! Yes, I certainly see that. Unfortunately, I believed I was purchasing precision state of the art engineering from a manufacturer founded by formally trained engineer.
Let's just be thankful his doctorate is in engineering and not medical!!!
But when I hear "method of failure #24", I feel compelled to write a letter to the Vienna University of Technology, who issued that degree, to inform them of their grave lapse of judgement.
No doubt, many talented people are of humble origin, which was not any point I was addressing.
I was highlighting the fact that Porsche prominently displays in its corporate name it's engineering credentials, which Porsche calculates the average person will rely on to ensure the product they were spending a hell of a lot of money on was of superior engineering quality. But that sadly, it's just not the case.
Consider this quote made years ago, today:
Ferdinand Porsche's motto was to produce automobiles which had to be reliable and of high-quality sports cars, of a high utilitarian value.
Jake do you have YouTube vids of all the modes of failure? I find them very interesting to watch as most of us don't work on m96 very much, if at all. Reminds me of watching those "How It's Made" tv series, except on a different level.
No, I discovered lots of them years ago and never did videos with them, but have photo documented them. The normal failures are just another day at the office now, but MOF#24 is one I was waiting to see, because we knew it would occur due to the design of the IMS assembly.
I waited for 5 years for that one to find me :-) I was so damn happy the day that we diagnosed this one.
I have included the failures in my M96 Engine Bible, but have not decided which volume to insert it into.
Jake you saved the day again! After reading your post, and viewing the video, I went to the garage, picked up the IMS, and MOVED the sprocket for the IMS chain! Without your input, I probably wouldn't have noticed this fault, and would have spent a lot of time figuring out why the cams aren't turning when I tried to time them.
All 6 pistons are marked by the valves, so I'll contact you via phone next week in re: used serviceable pistons-along with another IMS.
Thanks again!
WOW!
That made my week, hell it made my month! I love helping to find these types of "smoking guns".
I tell people all the time in my classes that you HAVE to conclusively find and address the smoking gun after a failure, else you'll do nothing except waste your time and break even more parts.
I may have an early IMS as well, after that drive comes loose its impossible to get it straight again without runout that will break timing chains.
So glad I was able to help.
