Recommendations for 150k Mile Maintenance

I am the original owner of a 1999 996 coupe. I ordered the car from the factory in 1997; it was built in March 1998, and delivered in May 1998. I have used it as a daily driver, year round, for the past 13 years and it is now turning 149,000 miles, getting ready for a 150k maintenance and a top-end overhaul. I have been a reader of this board for the last 5 or 6 years, and I am familiar with the RMS, IMS, and Nikasil/Cylinder-piston/rebuild issues and options, so I have reviewed in detail the posts from members that have gone through a complete rebuild using LN engineering parts. Many thanks to those of you who have posted so much information, with detailed pictures and notes from your hands-on experience. I would like to get your feedback/recommendations on three options I am considering for a 150,00 mile overhaul. The engine currently runs strong, no power or idle roughness issues. No oil consumption issues. However, I do have some chain rattle at start up, and some moderate/minor lifter noise. It has thrown some CEL codes related to variocam timing �at limit�. It appears that the variocam chain tensioner pads, and possibly the chains themselves, are worn, and need to be replaced. I had my local dealer pull the oil pan and oil filter to look for any debris, and everything was very clean. No metal or plastic bits whatsoever. I also had a compression check done with these results: 1. 155 2. 140 3. 150 4. 160 5. 150 6. 150 Since these are all within 7% of 150 psi, and oil consumption is normal, I decided not to do a leak-down test. My goal with the car is to continue its use as a daily driver; no track events, etc. I�d like to put it in shape to be as reliable as it has been for the past 150,000 miles, to extend its use to 200,000 miles (which should be another 2 or 3 years for me) at which time I can consider a major overhaul or upgrade to another vehicle (a new 991 would sure be nice ...). Here are the three options. Option 1: �Minor top-end overhaul�: R/R engine to facilitate the following tasks replace variocam chain tensioner pads and chains (i.e., chains #4 and #5) clean/inspect variocam actuators and test variocam solenoids; replace if required replace all 24 lifters replace the chain ramps, tensioner pads, and external tensioners for cam chains #2 and #3 replace external tensioner for Chain #1 (IMS) replace air/oil separator (AOS) and attached tubing replace oil cooler o-rings to repair minor coolant leak (known issue) all standard 150K mile service items w/new plugs, plug tubes, o-rings, etc planned IMS and oil system longevity enhancements: install LN IMS replacement kit for dual row IMS bearing install LN low-temp T-Stat kit install LN spin-on oil filter kit install LN magnetic oil drain plug since engine will be out, and transmission off: replace most vacuum lines or rubber hose lines where practical (engine 14 years old) replace water pump (was replaced previously w/failure at 120K mi) as precaution replace clutch and t/o bearing (first replacement was at 100k mi) to save future labor Option #2: �Major top-end overhaul� This would include all of the above, plus removing the heads, w/new valve guides, seals, seats machined, etc, at specialty shop. I would like to avoid this expense, although it would allow a look into the cylinders to check for any of the 996 cylinder/block �issues�. However, since everything seems to have been fine for the last 150K miles, not sure this is necessary at this time. Don't want to venture in here if I don't have to. Option #3: �Complete overhaul� This would include all of the items above, with a complete block teardown, LN Nikasil cylinders, new bearings, and IMS upgr adewith replacement of IMS chain#1 and related chain rail and tensioner pads, and cam chains #2 and #3. Basically, a Raby or equivalent re-build. Would possibly consider 3.4 to 3.6 upgrade if the cost differential is insignificant, but this is not a major (performance) issue to me. Summary: My preference is to do Option #1, and drive the car to 200k or 225K miles without any other work other than routine maintenance. The local Porsche dealer here is excellent, the mechanics are pro�s, I have seen their work on other 996 and 986 engines, they are experienced with LN IMS retrofits, etc. They will do all the work, not me. My question are: 1. Am I leaving anything out of Option #1 that I should include? 2. At this point, I really do not want to go into Option #2 (pulling/refinishing the heads). Am I being short-sighted here? 3. Option #3 is expensive; would like to put this off until past 200k to 250k miles. However, I would not be opposed to doing the full Nikasil re-build sooner if I run into piston/ring/cylinder/intermix issues, which at this time is not the case. Your thoughts? FYI, this has been a great car as a daily driver for the past 13 years. I changed the oil about every 10,000 miles, thinking it was better than the factory recommended 15,000 mile interval. In retrospect, I probably should have done them at 5,000 miles, and will do so in the future. The car was never tracked, but it has not been babied, either. It gets washed twice a year whether it needs it or not (silver is a great low-maintenance color) and it still looks pretty much like new. Any input/advice would be greatly appreciated.

Option #4: Leave the engine alone. The cylinders/pistons/et al appear to be ok or you'd see misfire error codes. The VarioCam related issues might be connector related or VarioCam solenoid related. You might explore replacing the solenoid on the cylinder bank that the error code pointed to. Maybe. Or you can wait and see. When my 02 Boxster's passenger bank VarioCam solenoid/actuator needed doing the chains that the tech and I could see, the chain guides/rails (composite plastic) showed very little signs of wear. Oh, and this after around 220K miles of use. Might add the engine's a bit noisier (maybe) so I switched -- just the other day at 252K miles... -- to Mobil 1 5w-50 oil (not a 15w-50 typo!). And I think after this summer instead of going back to Mobil 1 0w-40 over the winter months I'll just stay with Mobil 1 5w-50 for both cars year 'round. Anyhow, the tech replaced the replaced the bad solenoid and actuator (with its new rails) and because of the small amount of wear present on the rails of the original actuator we didn't even bother to remove the camshaft cover of the other cylinder bank. Back to your car and its engine: Since the engine has made it to nearly 150K miles just keep doing what you've been doing. Its working. Sincerely, Macster.

Macster, Thanks for the thoughts re: Option #4. That's actually very appealing. I had made the (possibly erroneous) assumption that those plastic chain rails would be worn out, based on looking at other 986 owner's parts on rebuild projects at the Porsche service shop. The trouble codes on my car are limited to one bank, your suggestion might be a good alternative. Are the solenoid/actuator parts available separately or as a single unit only? I remember using 5w-50 in my 1989 911 Targa (since sold) and have looked here (Omaha) for Mobile 1 5w-50, but can't find it. Can't find it on the Mobil web site, nor at Amazon; do you have a good source for this? Have you done an IMS replacement? I have the dual-row (original) bearing at 150k miles, don't know if its a time bomb or not ... Thanks again for your help. jm

You have to pull the cam covers to get to the solenoid. I had 105K when I replaced the variocam chain tensioner pads in mine and they were very worn. I replaced all three chain tensioners (IMS badly scored/1-3 light scoring/4-6 looked new). Everything else internally looked like new. My IMS bearing was good, but got replaced with the LNE one, AOS replaced (blowing oil out the 4-6 vent), and replaced clutch and water pump.

you are my hero OP.

Excellent well thought out post, especially for your 2nd post. I say you need to have the camshaft timing deviation checked to help your decision, I would be surprised if the VarioCam chain wear pads did not need changing to the new improved version now & definetly before 200K miles. Options 1,3 & 4 seem to be good plans. I would be careful of plan #2 because 1999 3.4's have the weakest cyl. walls & rebuilding the heads can cause decreased piston ring seal. Also consider what your plans for the car are 2-3 years from now when you reach 200K miles, resale value needing engine rebuild vs. having recently rebuilt engine. If you do pull the engine out now to do option #1 you essentially hold a $1,500 coupon good toward the other options.

Just out of curiosity..., How much can cost option #1 Thanks Robert

Byprodriver, Thanks for your input. I agree with you re: Option #2, I have a fear that if I go into the heads i may well end up sliding into a major overhaul. Would prefer not to #2 or #2 right now. My 2 to 3 year plan would be to have a solid vehicle with a relaatively new top-end (all the cam chains and tensioners relatively new) and IMS upgraded so that it would have decent useful life for the next owner; or perhaps, depending upon the changing fortunes of time, I might elect to do a full rebuild to "better than new" condition with Nikasil cylinders, re-done heads, etc. Question: can option #4 (single bank variocam actuator/pad assembly repair/replacement) be done with the engine in the car? And, given that this is an early-build 3.4, is it too risky to wait for the other bank variocam actuator/pad set to begin to fail rather than replacing both right now? Thanks again for your input.

Robert, I am still getting quotes for parts and labor, should have details within a day or two. jm

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+1 If it ain't broken, don't fix it

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Did you really just say 250,000 miles? for real? That's impressive. Have you had to do any major work to the engine? Sure makes me feel better about my "investment" in my C4S as a daily driver...

Speed, Macster, Yep, I would like to leave it alone, unfortunately the CEL codes I mentioned above are coming more and more frequently, to the point where the CEL light is on most of the time. Mechanic checked codes stored today, they do show some misfires on the bank with the variocam range limit issues/codes. At a minimum, I am going to have to have the variocam on one bank pulled and repaired with new chain/pads/ and possibly actuator and/or solenoid. I will have them check circuit integrity first to make sure its not a signal problem to the variocam solenoid. I suppose that if the chain and pads are OK on the faulty bank, I could assume that they are OK on the good bank, and just drive it until any further problems occur after repairing the actuator and/or solenoid on the faulty bank. I just don't want these (early 1998 build, original design) variocam chain pads to wear down into the metal and start sprinkling metallic jizzum into the engine's oil supply. So, I've got to do at least Option #4a: Fix variocam problems on bank 1, leave everything else alone or ... Option #1: Do top-end overhaul, don't touch the heads/valves, leave major overhaul to later (250k miles or later...) Thanks everyone for the advice and input jm

OMG!!!....150k and no IMS or RMS.....or even AOS??? or is that AOS' ? there's 2 or those, right? all ways awesome to hear our cars can really do this. Continued good luck to u !

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Yes, I really said (typed) 250K miles (252K and change as of today). The only internal engine work -- not counting a water pump at 172K miles -- the engine has required was the replacement of the passenger side VarioCam solenoid and actuator, about a year ago -- at WAG 200K to 220K miles -- at a cost of around $3K at a handy Porsche dealer service department. You bought a very good car. Just give the car reasonable care and servicing and stay on top of the little things -- like had I ignored a noisy water pump the pump may have come apart and ruined the engine -- and enjoy what should prove to be a very nice car for years and thousands of miles to come. Sincerely, Macster.

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The misfires are likely caused by the VariCam problem as the DME attempts with to adapt to the very odd O2 sensor readings and the fueling gets out of whack. Upon my drive home with my Boxster's bad VarioCam solenoid/actuator I looked at short and long term fuel trims and noted they were quite different from what I was used to seeing. At the dealer the next day the tech confirmed that that short/long term fuel trim behavior I had seen and reported to him was consistent with the VarioCam solenoid/actuator being bad. Had I driven the car longer the engine might have developed misfires and stored codes for these, along with codes for adaptation errors and of course the VarioCam related errors too. If your tech confirms the VarioCam solenoid/actuator is the cause of the VarioCam related codes by all means replace the solenoid and actuator with new parts. You will have the new hardware and the old hardware in front of you. Judge the amount of wear and based on this determine if the wear is bad (enough) then replace the other bank's actuator (I do not think the actuator rails are sold separately but if they are then replace just those). If you have then have clear indications your engine's 'eating' rails (so to speak, cause at 150K miles it is not eating them at a very fast rate), that is signs the rails are wearing in your car's engine at a high rate then you might consider going 'deeper' and replacing other camshaft guides/rails. The trouble is some of these can IIRC require splitting the cases so you want to be sure this is necessary. In my car's case the bad actuator's rails showed very little signs of wear and there was no need to go to the expense of pulling the other camshaft cover off. Had the tech recommended it of course I would have. Before he even removed the camshaft cover off the engine on the passenger side we talked about replacing some rails on the bad bank and even on the other bank. But he told me let's wait and see what the bad side's rails/et al looks like and only if there are signs of extreme wear -- enough to justify the cost of replacing these (which ain't cheap) -- would we worry about the other (good) bank. Another thing I learned is more often than not if the solenoid is bad the actuator is too. In the case of the Boxster the solenoid and actuator are a 'big' job to get to and replace. In the 996 engine, at least this is what I understand, for some years anyhow the solenoid is an 'easy' job. If it is then replace just that -- unless your tech advises you differently -- then see if the actuator is bad. With a bad solenoid the techs tell me there's no way to id a bad actuator until the solenoid is replaced. But the work to go back in and replace the actuator vs. just replacing it while one is there (on the Boxster engine anyhow) is a lot less work, read cheaper. Sincerely, Macster.

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A top end overhaul at 150K and then a major overhaul at 250K miles means the 100K miles between 150K and 250K mile is going to cost you plenty. Then every mile after 250K will cost you plenty more. You'd have to drive the car maybe to 500K miles to get your money's worth out of the top-end and major rebuilds. That's a long way into the future. I like my Boxster even with 250K miles on it. The car and engine run good. But it took 10 years of driving to get 250K miles on the car. While I would like to get 500K miles out the car/engine I'm not sure I'd want to be driving this car in another 10 years. Will you want to be driving your car in another 10+ years? Up to you, of course. Based on the fact that the car has 150K miles and has not done anything worse than possibly suffer a VarioCam solenoid/actuator failure suggests it is not wearing out. I mean if there was any wear of the other moving parts I think you'd know it by now. When my motorcycle engine (Honda CB750) lost a camshaft lobe (due to the fact I failed to change the oil on time) it didn't take 150K miles to go flat. The engine had maybe 30K miles on it and it went flat in a few months of driving in a very wet/cold winter. The engine went into the fall months quiet. After January it was ticking. Diagnosis: flat camshaft lobe. For the sake of an inexpensive oil change I had to pay hundreds of dollars to have that camshaft lobe problem addressed. And back then (early '70's) hundreds of dollars was a lot of money. Look at the rails but with 150K miles if they were wearing at all they'd be worn out by now, coming apart by now. But I could be wrong, so see what you find, hear what your tech has to say. Sincerely, Macster.

Uh, i drank too much scotch tonight to read your whole post but from hat I gather I will comment. Do not fix what is not broken. However, if you decide to rebuild the motor replace all wear items.. Id list them but uh... I'm uh.. U know...

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To the OP and Macster:

Thankfully we have Macster's voice of reason and mechanical clarity in the 996 forum.. I'm just diluting the post. My apologies to OP and Macdaddy.

Ah, Hardback, I see that you have already updated your car with LN Big Nikki's and other fine stuff, no wonder you can sit back now, relaxed, with a bottle of scotch, and watch the rest of us sweat! I'm envious! jm

Macster, I think you may be right with your approach, it makes the most economic sense. I think I will have the techs pull the cam assembly out of the 1-3 bank and see what we've got. I should probably do the LN IMS replacement as insurance against the big chill between now and 250k miles. Thanks for your continued support. jm

rb, Thanks for the information. I am going to do the LN IMS also. The dealer here in Omaha stocks LN parts in inventory, and has "package deal" to do it; they have already done several for 996 and 986 owners in the local area. jm

If you deside to go with the IMS retrofit, could you take the old bearing apart and post some pictures of it? Recent updates on IMS bearing "hype" are suggesting that the dualrow bearing is much better/stronger than the later desings.

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Couldn't disagree more.. Elective procedures just make sense with these engines. After any failure occurs the cost of the engine reconstruction goes through the roof and in some situations the engine can't even be used as a core. Running an engine to death is the most expensive mistake that can be made, no matter if its a Porsche or a Chevy. With 150PSI you have lower compression numbers than I'd expect from a healthy engine, BUT looking at these numbers and the differentials between different cylinders I'd be willing to bet that you didn't have the intake butterfly locked open during the compression test. It is imperative that the butterfly be locked open, else chamber filling will be less and the efficiency of the intake is illustrated in the compression values. Basically if the chamber filling of the cylinders is less due to the intake being obstructed by the butterfly being closed, the compression will be dramatically lower. If the air can't get into the cylinder the compression values will be lower. Was the butterfly locked open during the test? Also, there is no "hype" about IMS bearing failures. The dual row bearings have always been the strongest because they have TWICE as much load carrying capability. Just because they are the strongest doesn't mean anything, because ALL of the bearing generations fail.