996 camshaft deviations and IMS

Hello Everyone, I am writing again about my sons' 2000 996. I currently has 43000 miles and we have found some small brown specs in the oil filter, thanks to the members who told us it was related to the rail guides. I also read that it's possible to detect a possible IMS fututre failure by using the durametric tool and read the camshaft position deviations between cam 1 and cam 2. We are scheduling a IMS replacement in a couple of weeks and will drive it only a few miles between now and then. Attached is the readings of the camshaft deviations. Is this an indication of immediate attention or is it in the acceptable range?

The factory cam deviation spec is 0 degree +/- 6 degrees so your bank 1 is slightly out of spec. As long as the cam deviation values hold steady across all rpm, it's unlikely you have an imminent IMSB failure. The deviation is a good indication of cam pad s wear but not a good prediction of IMSB failure though.

Forgive my limited knowledge, but if I understand you cam 1 is .48 out or over the acceptable range. It did hold steady throughout rpm range. Now this is more of an indication of cam pad wear not a good indication of IMS failure? And the cam pads, are those the chain rail pads that we have a few brown particles in the oil filter from? Thanks Joe

Yes, all correct.

Ok hopefully my last question. Replacing the IMS was to be done soon and is expensive enough. Is it possible or recommendable to only fix the cam chain guides on the cam 1 side only. We found about 30 specs of brown specs in oil filter. Or can this be monitored and continue as is for years with no problems if the deviation doesn't increase?

First be sure the cam reading is corect. The motor has to be hot. Not idle in the driveway until it reaches the 180 mark hot but driving it hard for an hour hot. Mine will vary from 5.4 to 6.6 ddpending on engine temp.

I guess I need to try it again tomorrow. I did take a reading twice but as you said not to do, I varied the rpms but took two readings in the driveway after reaching 180 degrees. I will run the car tomorrow for an hour and then take new reading and post. Thanks

The cam deviation itself cannot tell you how much is worn on each side because you don't know what the original values were when the cam pads were new. The difference tells you how much is worn (getting more and more negative). So it's possible that both side are worn. Unfortunately I don't have a good answer to your questions how much longer they will last if left unchanged. They are designed as a wear and tear item. To be safe though I think it would be wise to replace both banks as they have similar mileage, than risking valve/piston damage if they go unexpectedly.

Cam deviations don't indicate an IMSB failure until the bearing reaches Stage III failure. By this point there's already metal laden oil in the engine. What you need is a set of variocam wear pads. Bank 1 always wears faster than bank 2 and these are the first thing that will give deviations. If I were pre- qualifying that engine for an IMSR, I'd have to consider this closely, because though the factory spec is 6 degrees, these wear pads wear quickly once they are worn through the epidermis layer of material. As the wear goes deeper and deeper, the surface of the pad is softer and softer. I always consider any issue that may occur down the road, and if we do an IMSR, anything that ever occurs with a cam deviation down the road is going to get that finger thrown at us as fast as lightning. It might take 60K miles to get to 6 degrees of deviation, but you can double that amount in only 20K more miles. This is what you'll find.

Joe.. Like you, I checked the cam deviation specs when I bought my Durametric back in 2010. Because I have a ROW spec car, I can only measure the deviation on bank 1 - there is no facility for measuring bank 2. Anyway, my deviation was -5.5 deg Crk which was slightly worrying. Then when I measured it with a hot engine it dropped to -5.1 deg, so nearly half a degree difference between a warm engine and a hot engine. I had also found a dozen rice sized grains of plastic in the sump, so I know that some wear has taken place, but the cost of replacing the ramps is not cheap, I've been quoted over $5,000 here in Australia. Because you already have your Durametric, just measure the crank angle every 2-3000 miles to make sure is not increasing. Mine has not changed in nearly 30,000km, but I still check it regularly.

Ok so I'm going to remeasure the cam deviations again today with the engine hot. And of course continue to check them. Is this my first priority to have fixed before the IMSR, and just how costly is it. I'm in Miami fl. Or do they both have to be addressed at the same time?

Doesn't look too bad to me. Here's what the one from my 2002 Boxster looked like when I had the actuator replaced at >250K miles when the actuator proved to be bad: Might mention the tech didn't believe the unit's condition warranted opening up the other bank to replace the other side, which I would have certainly agreed to had he recommended it. Might also mention the car has been back on the road for nearly another 50K miles. Here is what a new pad looks like: But very quickly after installation the actuator looks like this:

Thanks again everyone for all your responses. Here's the latest, I went for a drive for over an hour, drove it hard as possible, this is Miami after all. At the end of an hour cam 1 dropped to 5.80, cam 2 never moved (pic attached). The car ran great by the way strong and a nice scream near red line. So my sons' car is just within spec and if I understand correctly with frequent oil changes and monitoring this can last for quite a while. So he can wait a while before changing the cam wear pads correct? Now if I also understand correctly he shouldn't wait any longer before replacing the IMS bearing because there is no warning for this device? As usual you guys were right on the money, and I thank you for your input and patience. Joe C.

I wouldn't worry about the IMS bearing to much either. I would upgrade it but many on here would not. The car is a 2000 and most likely has a dual row bearing from the factory. Most 2000 model cars had the dual row but not all, the only way to know for sure is to look at it which requires the trans to be out. The factory dual row bearings found in all 99 and most 2000 cars have a very low failure rate compared to the later single row bearings. I had mine replaced and its a 2000 that already had a dual row in it. In my mind tour car has very low mileage and if it has not shown metal in the sump up till now then it is doing well. Its IMPORTANT to get a good installer for the upgraded bearing. I think you should call FLAT SIX and ask JAKE RABY to recommend one in your area.

I second JD above as you most likely have a dual row IMS. I have a 2000 as well with 152K km (94.5k mi). No real rush to get this done at that mileage but only you know, how much risk you can stomach. Thanks for your query on deviations. Learned a fair amount from responders. Enjoy the car!

I too have learned a heck of a lot about this as well. Is there any way to tell from the vin or birth date of july 2000 that this porsche has a single or dual row ims without taking it apart? I do feel better having talked to all of you and that I do have time to make a decision and find a qualified technician to replace the ims. Thanks Joe

No - you can't tell until you eyeball the IMS bearing cover. If it makes you feel any better (??) my Feb 2001 build Boxster S had the dual row bearing when I replaced it in 2010. But it's really a crapshoot and you can have either bearing installed because event though you know the assembly date of the car, you don't know the build date of the engine.

Quotes source post: 12307009

Bingo. I've been tracking my cam deviations for the last 3 years, and I thought they were 'fine," as I was seeing -3 and -1 on each bank (a difference of 2). But my mechanic discovered worn tensioner pads on bank 2, and we gained a few degrees of deviation when he replaced the pads on the passenger side. He said that I should go after the driver side now, even though I had a solenoid replaced 5 months ago. So while I don't want to go back in there and spend double money (he said the cams actually have to come out now because the tensioner on the driver side is positioned differently, so its even more labor), I really should just do it. And yes, my car has 64,000 miles. I didn't want you to be right about it, as I cannot believe a design like this would require this level of effort at only 60k miles, but I guess it's the way it is.

I just checked my cam deviations for the first time, at 52k miles, with a Foxwell NT530 OBD reader. Cam 1 deviation is zero, and Cam 2 is -3*. Two questions: Many rennlisters mention +/- 6* as the allowable range. Is that each cam from 0*, or the spread between Cam 1 and Cam 2. This has never been clear to me. If Cam 1 is at +3*, and Cam 2 at -4*, is that within spec (both less than 6*) or out of spec (spread between them in 7*)? Which cam is driver's side / left side? Thanks.