Using Durametric to Detect IMS Bearing Weakness
 

Hi Folks,

My '03 986 is under warranty for a bit longer, so I thought I would use my new Durametric software/cable to detect any sign(s) of weakness in the IMS bearing. I read someplace about using it to determine if there is a cam variance within the engine. Can someone point of which specific measurements to look at for this?

Thanks,
Ron

Correlate the Camshaft Deviation between position 1 and position 2, they should be close in degrees. Before I replaced my IMS bearing my deviation was .60 degrees different between the two.

Thanks Jager, I'm going to do a quick check with my laptop and see where my deviation is.:cheers: Praying for a 0.0.:dance:

Thanks -- I'm going to run that test when I get back home in a few days. And I'll flip if it's near there. :(

Next time I buy a Boxster I'm bringing my laptop and Durametric cable for the test drive!

Are these cam shaft parameters easily read from all OBD port scanners....can I get it on my iPhone?

I dont know too much about durametric software and the required hardware. What are all the uses and are there any alternatives? What is the cost and where can one buy the equipment?

Diagnostic Tool for Porsche | Durametric

Google is your friend.

I've only had the chance to use my new Durametric cable/software a few times, but as both a tech guy and a Porsche guy I'm thrilled with it. Knowledge is power, and with the Durametric you can see everything the car's multiple computers see. Far more powerful than a mere code reader. Check out their videos, which provide a pretty good explanation of what it is capable of.

For $300, it is the best money you can spend on your Porsche.

What you should be looking at is if the cam deviation values remain steady at idle. The actual values are irrelevant, as long as they do not exceed the OEM specs (+/- 4 degrees on five chain M96’s). If the values are not rock steady at an idle, and swing back and forth, the IMS bearing is most likely on its way out.

As for what tools will give you this data, PST II, PIWIS, or Durametric are your only choices; and no, nothing exists for the iPhone……………

Keep in mind that the bearing/race contact area starts to get rough when the lubrication breaks down and the first particle is shed. The wear then accelerates.

So depending on a check of the oil filter media, a magnetic drain plug, or a deviation check is no sure thing because you aren't going to do any at a frequent enough interval to catch the problem with any probability before it is spraying significant debris into the oil passages and or taking out the sprocket/chain interface leading to valve clash.

Sure you can get lucky and catch it but the probability is against it.

Just to add to my previous post... My old IMS bearing was not falling apart but close inspection there was a little movement between the inner race and outer as shown in the picture. This bearing might have gone another 200k miles... Who knows?

Yes, I replaced mine with a retro-dual row. My bearing(s) were in great condition but there was another guy in that day that was not so lucky.....just on the verge of disintegration. He was faced with a long process of monitoring oil and oil changes to try and catch any debris.

I would like to monitor the health of the new bearing as well as tensioners. I figure that my oil change intervals would be suitable

I am running the diagnostic now, comparing Cam Deviation 1 and 2. They do NOT change while the engine is idling. Cam Deviation 1 stays at 0.64, and deviation 2 stays at 0.66.

See pic below.

Since the deviations are within the norm and do NOT change, does this mean we do not have a problem indicator with this test right now?

Very good numbers Chairman. The thing to look at is the variation at idle and if its rock steady, you are ok.

But the cam deviation is just one diagnostic for IMSB condition. Some say cam variation occurs only in the very late stages of failure, right before detonation. Noises, like a rattle at idle or a sound like a waterpump going are also signs of a bad IMSB. And of course, metal in the oil filter and magnetic oil drain plug are almost always a sure sign of impending failure.

Theres also the question of how much warning you get from the time the bearing begins to go until total failure. If that period is less than your oil change interval, then you are not going to catch it by oil filter inspection.

For a very legnthy discussion on warning signs of impending IMSB failure, see this discussion on Pedro's Board. IMS guardian

I use cam variation, filter and drain plug examination and a stethescope to listen to the area around the IMSB to check the condition of the IMSB, but the only real guarantee against failure is to get it replaced.

What's the typical cost of an IMS bearing replacement on a Tiptronic vehicle (no clutch jobs being done anyway)?

Around $3k for a TIP.

Does a bearing retrofit require the engine to also drop, or just the tranny?

No need to remove engine.

A picture pulling IMS bearing while the engine is still in my car.

JFP,

You say the actual values are irrelevant but they must mean something. I just took my readings and I'm at +.39 position 1 and +1.93 position 2. Those readings are rock steady at idle all the way to 5,500 rpm. I've been on other forums and sites reading what I can and I've seen everything from positive deviations like mine and minus deviations. Are you saying it's all in the delta between the two?

BTW, I have an '04 3.2 so I think I have a three chain. Are those numbers for my engine also?

As long as the values for cam are between +/- 4 degrees (OEM specs for the M96/97), the actual values are irrelevant as they represent tolerances in the VarioCam, chain slop, component wear, etc. Try as you may to get it on the “ideal” deviation value of “0” when assembling one of these engines, you never will and will always end up with some value that should be in +/- 4 degree range.

The critical issue for determining if the IMS is on the way out (and this is a “win the lottery” odds of actually seeing it before the unit blows) is are the values rock steady at an idle; if they are not, and are moving back and forth, something in the cam drive, usually the IMS bearing, is wobbling badly.

JFP,

With that philosophy, and I know Jake did his homework on his Guardian, but what if there was software that was constantly monitoring this data which the computer already is. Then have that monitoring trip an Check Engine light when the cam deviation fluctuates or goes beyond a predetermined value (+/- 4 degrees)?

This sounds like more of a tell tale sign of impending failure than a chip detector...even have a safety net and if those values are exceeded, shut the engine down to prevent catastrophic failure.

Sound like a wiener?

P.S. If shutting down the engine sounds dangerous just think if it hand grenades in traffic.

Problem is that when the IMS is wobbling emough for the Durametric (or PIWIS) to see it, there already is metal all over the engine that will need to be cleaned out before putting it back in service. Jake's approach sees something wrong much earlier, before the inside of the sump looks like a trash can under a machine tool..........

Yes I am with you....this was my ims gaurdian guess but I was wrong....just didn't think about a simple chip detector. Chips can come from anywhere so it would go off from things other than just the ims bearing; I was thinking ims bearing failure isolation. I don't believe you would be able to catch chain tensioner wear with the
guardian (plastic is not magnetic). Cam shaft deviation monitoring might be able to give you tensioner wear due to increased chain slop and loss of motion. This what is what I was most interested in as I have changed my bearing. I guess it was just wishful thinking.

If chain tensioner wear can be shown to produce cam shaft deviation we may have our own product! We could perhaps monitor cam shaft deviation via the OBD port and have an alarm go off when deviation goes outside of 5 degrees. I was thinking of just connecting your iPhone to the OBD port to do a check every so often.

Oh well...I suppose Durametric has this covered already!

I'm with you Jaykay, I believe monitoring the cam deviation in concert with a chip detector is the way to go. Alarm at 5 degrees?, I'd go with .5 degrees. Any fluctuating deviation is not a good thing, slop is slop.

It can't be hard to monitor those two values and then trigger some sort indicator. This can't be that tough to figure out and then we can all sleep a little better at night. I'll get right on it.:D

Yes thanks for the decimal point....yes fluctuation with respect to each other

I am glad you are the electronics wizard!

Maybe an engine builder could speak to the exact nature of deviation with respect tensioner wear

My shop is telling me that with a TIP 986 replacing IMS requires dropping the engine too. Is he wrong?

Brilliant idea.

By the time any valve timing deviations occur the engine has already been subject to foreign object debris from the failing bearing that HAS to have degraded enough to allow for the deviations to e measurable. Collateral damage from foreign object debris wear metals from the IMS bearing have always been the primary modes of engine failure with IMSB failure.
There are lots of issues with measuring camshaft deviations and I know these because I have tried it.. Wait till a tensioner gets lazy or you have thick oil on a cold morning, or under heavy deceleration. What's is supposed to happen in theory doesn't happen. False positives would happen daily.

Just hooked up durametric for the first time. "Cam 2" is showing a deviation of 3.39 deg. Is this getting too close to being out of spec. and does this camshaft need to be "timed". Deviation fluctuation is rock solid at idle.

From what I understand, the values are not as important
 

as if the values are fluctuating. If the numbers are not changing then I think you are okay.

i've seen both +/- 4 and +/- 6 stated as acceptable limits. watching the numbers with your durametric will tell you two things:

- fluctuating values tell you your ims is wobbling.
- values that slowly increase over time (months, years) speak to deteriorating tensioner paddles (bits of green plastic in your oil filter) and need for eventual rebuild (3.6!!!).
- values that start high are probably due to mis-calibrated sensors from the factory.

okay great.....thanks guys

I guess 4 degrees is nothing when you are dealing with chain lash!

I have a deviation of 2.0 and -6.0. I'm guessing this is bad.....?? Should I flatbead it to my mechanic??? What say you Boxster Gods??? :barf:

The OEM spec has been both +/- 4 (early M96) and +/- 6 (later M96/97).

Don't panic just yet; if the values are steady (not swinging back and forth and idle), it is probably just wear on one of the tensioners, chain paddles, or a VarioCam unit. These are problems that can be addressed when time and funds permit.

If the deviation values are swinging wildly, shut the car off and call the flatbed.....

There is mode that can plot the deviation in real time as you idle. As far as I recall you call up cam one and cam two. The display seemed accurate enough to show variance in deviation; you should have flat lines for both parameters. There is also a numerical display that can keep your eye on

They were rock steady at idle. No deviation at all, let run for 5 minutes. I am still contemplating the IMS/RMS upgrade as a precaution. I have a mechanic (Provost Motorsports) who runs a $2k special to replace. Any idea on the price of the tensioners, etc.?? Thanks for the replies!

I checked my deviation today and I get -4.5 and -6.3.

It is rock steady and does not fluctuate.

Sounds like its slightly out of spec.

What does it mean, timing chain is a little loose?

How do I correct that deviation?

Do i need new chain guides or tensioners?

I have a 2001 S with the 3.2l and 60K miles.

Could be either the chain guide wear paddles or the tensioners, you would need to start looking to see which or if it is both (not uncommon). Could also be the VarioCam unit.

I found that once I switched to a 5w40 I saw much less plastic material in my oil filter. This may be just due to chain run in on the plastic earlier on in the cars life vs later when chain grooves are more established

I do continue to see little flecks of what looks like vario cam pad material....perhaps as a result of my driving style. I am up and down through 4k a lot on the street.

Anyway perhaps a different oil may help you in the future