Cam Deviation to Detect IMS Failure Progression
 

I can't seem to find it now, but I read a thread that said you can use Durametric to view the cam variations for early detection of IMS failure. I looked at mine today and it stays at a pretty steady -3 degrees. Does that mean I should be fine, for the time being?

If anyone can find that thread, please let me know...

Hello !

Here is the post Camshaft Deviation fluctuating in Durametric . From what others have stated re the camshaft deviation here, I think you are good to go. But, checking your oil for shavings and other matter is a good idea. Hopefully JFP will chime in and give you more info.

Rod SmileWavy

Normally, the cam deviation values will be some odd values between +/- 6 degrees, but the value will remain rock steady at an idle (your Durametric should draw perfectly straight red and blue lines in the graphical display). If either of these cam deviation lines starts to gyrate back and forth at idle, something in the cam drive, usually the rear IMS bearing, has become very loose, allowing the cam timing to jump around. Unfortunately, these movements are subtle enough that the engine shows no apparent signs of an issue (and no codes) other than perhaps a commonly noted “metallic rattling noise”. As the result, you rarely catch the engine demonstrating this symptom before all Hell breaks loose. If you ever do see this happening, it would be very wise to not run it until investigating the problem further.

http://i1140.photobucket.com/albums/...g?t=1309381620

I too recently ran the Cam deviation values on my Durametric....both were rock steady, Cam 1 .067 and Cam 2 -1.28, it helps to put your mind at ease, but I still keep changing oil at 3000 or every Spring. ;)

The only problem I see with all the detection methods cited is they are employed at intervals. No matter if you inspect filters, use a magnetic drain plug, or look for camshaft deviation...are you doing it often enough that you will detect the problem between the time the problem is detectable and the complete failure point? You can catch the problem but you have to be lucky, don't you?

If you are worried about IMS failure, don't you need a detector which checks at sufficiently frequent intervals that it can detect before serious damage is done...or just a better IMS bearing that gets lubed a different way and so doesn't fail?

I recently collected a 10mn drive data.

1- Cam deviation steady whatever the RPM, thought I notice a slight increase toward the end of the drive (say from -3.7 to -3.6)

2 - Actual angle is either 0 or 25 deg, depending on RPM

I have only one sensor because it's a RoW car, so I can only take measurement on Cam 1.

Hopefully,getting only one measurement is enough to get some feed-back on the IMS condition.

PS: I also plan on doing time to time measurement for benchmark purpose as well as getting the IMS Guardian, change my oil once a year/5000 km, use full synthetic 5W40 and rev >2000 RPM after warm-up.

Mike, is it fair to say that the window of opportunity to dectect a possible failure does excist? Its just not possible to dectect the actual time frame?

Rod :eek:

Let's put it this way: The last car we had in the shop that we "caught" the cam values acting up, I suggested the owner go buy a couple of lottery tickets as it was his lucky day; it is that rare to actually see one on the way out...........

Here is how I understand the issue...

There is a window...at the point the seal has broken down and the bearing itself starts to wear in its race because it is no longer effectively lubricated. At this point the bearing starts to get rough and then to shed parts of the bearings into the oil but the bearing in total is not wobbling enough YET to cause the shaft to wobble to cause the sprocket to wobble to cause catastrophic failure. IF you happen to do your inspection at this time and see the debris or deviation and understand it and get the car immediately flatbedded to someone who can remove the transmission and replace the bearing while also removing/cleaning the oil pan and thus removing debris from the system lest it clog one of the little oil passages...then you can most probably save the engine. But if you miss that window or miss the symptoms...

The problems are two: you have a possible bearing/lubrication failure and you only check every so often.

The possible solutions I know of are two: get a much better bearing/lubrication-method or check all the time.

Of course only a very small percentage of the seals/bearings fail when measured on a car/year basis. No one knows the exact percentage. Which makes economic analysis of the various options kinda tough.

Thanks Mike & JFP,

So what is the time frame/window from start to finish regarding IMS failure? Sounds like maybe seconds to a few minutes and like JFP said its like winning the lotto if you can catch it between the start and finish of the failure. I'm wondering if using the Durametric is worth it, re trying to figure the probability of a failure. Some of the Porsche owners here are assuming the probability is low because their deviation read-outs are minimal. Is this wishful thinking?

Rod :eek:

The Durametric system is very valuable for many reasons other than this one. As for catching an IMS failure, sometimes an owner has heard a noise for sometime, and never thought to have the car looked at; other times an owner is happily driving along with a car that has shown no noise or other issues, and “bang”.

We look at the cam deviation values as a screening tool; sometimes you get lucky…………

I have limited data points, but my car, '99 with 31,000 miles, had a 'loose bearing' which was obviously worn, and wobbled on the center.

I caught it during a clutch change, we did not measure the deviation before. No noise, no metal in filter. But because of this, I think there is more than a few minutes 'window of opportunity'

Again, not many data points, but it seams low miles cars have more issues than high miles, maintained cars, just from reported cases here.

Longer than minutes usually
 

It all depends what condition the oil is that washes out the bearing, how much and where the seal fails (more is better), the use of the car after failure starts, etc. It isn't like the bearing goes no lube all at once generally. And there are several variables.

One of the experts has said there are 4 stages of failure and he has seen bearing assemblies in each failing/failed stage. He has even taken a failing bearing assembly out of a customer's car and installed it in one of his engines for learning purposes. That implies to me the time can be more than just a few minutes.

But we also know of original bearings that are driven 200k+ miles.

Is there really data to suggest low mileage cars have more IMS bearing problems. On our 98 I changed ours to an LN at 25,000 miles and it was tight. I view it as insurance and preventitive maintenance.
Not many data points ignores oil changes, driving style and bearing quality control at manufacture etc.
Ron

One of the experts says he sees a lot more low mileage cars with problems than he should. Data...not exactly. Observation...perhaps.

Could his view be skewed by low mileage owners being more able to afford to get the car worked on versus working on it themselves? Sure.

But then he says he sees better bearings in high use cars where the oil is changed frequently. Could that be because the owners are more in tune with their car and recognize problems early?

More high-mileage owners have had their clutch replaced and maybe their bearing? Or is it the cars sit less time with less water in the oil because they are warmed up more/longer to burn off the condensation?

And higher rev'ed car fail less? TIPs fail more?

There isn't any real data, just observations over hundreds of cars a year...

Course of Action
 

This is all great information. Thanks for sharing. Since I'm far from being an expert, I rely on the data available as well as the experienced observations of experts.

Based on these posts, plus other information out there (both on this forum and the many others like it) my decision is:

- use oil on the Porsche approved oils list
(so far, sticking with M1, but may try other syn oils that may be cheaper)

- change the oil at least every 5K miles
(considering 0W-40 winter and 10W-40 summer for Alabama)

- pay attention to any "clues" that may come out of the oil drain hole
(just did an oil change, so next time I'll install the magnetic drain plug)

- connect the Durametric to see what the cam is doing, fairly often
(monthly possibly, about the time I usually do the tire pressure check)

- when it comes time for a new clutch, do the IMS bearing upgrade along with it
(helps to ease the cost to be able to share some of the labor with another job)

- drive it well, drive it often, and not worry about it. If I catch an impending failure, cool. If not, at least I tried.
(wohoo!)

All good info here. I'll add in few thoughts of my own regarding IMS failure not backed up by hard data but consistent with what other experts are saying. In my day job I train and supervise technicians who change out failed bearings in electric pump motors and the premature failure mode is very similar:

Water infiltration into the bearing is the enemy. Once water gets in there the bearing begins to rust and corrode causing premature failure. In the m96 motor the IMS is at the bottom of the case in a good location to collect water. A car that makes a lot of short trips or sits out winters in the garage has a higher incidence of water in the crankcase and allows plenty of time for bearing corrosion to take place. Cars that are driven daily to full warmup temp or driven often in a spirited fashion are much less likely to accumulate water in the crankcase and the bearing is regularly lubricated, inhibiting corrosion.

The other potential cause of premature failure is putting heavy loads on the bearing by running at low rpm or lugging the car. Once the rpms are in normal range centrifugal forces come into play and there is very little load on the bearing. Start and stop, low rpm loads, or lugging the car before it is fully warmed up and lubricated put tremendous loads on the IMS bearing.

How can we use this info to prolong the life of our cars?
*Drive easy but don't lug the motor during warmup.
*Take a spirited drive at least once a week to eliminate water in the crankcase.
*Change the oil every 4-5k miles. Watch your filter for shiny bits.
*If you winterize, change the oil just before putting her away and consider taking a spirited drive with the fresh oil to purge any residual water in the case.

So we need a constant way to chack the cam deviation!
Maybe this is what Jake Raby is doing with his IMS failure detector. Maybe it connects to the computer, and constantly checks the Cam deviation. That way it could tell in an instant when the Cam deviation starts to fluctuate. Thoughts?

By the time camshaft deviations are noted collateral damage has already begun. See the Tech Forum in the November issue of Excellence for the unveiling of my technology.