Using Durametric to Detect IMS Bearing Weakness

[jaykay]

Originally Posted by JFP in PA

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.

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.

[papasmurf]

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

[The Radium King]

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.

[jaykay]

okay great.....thanks guys

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

[navyc130fe]

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???

[JFP in PA]

Originally Posted by navyc130fe

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???

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.....

[jaykay]

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

[JFP in PA]

Originally Posted by The Radium King

i've seen both +/- 4 and +/- 6 stated as acceptable limits.

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