E46Fanatics - View Single Post - BMW won't recall defective water pumps (but Toyota will...)
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Old 12-01-2012, 08:55 PM   #64
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Join Date: Sep 2012
Location: Louisville, KY
Posts: 3,299
My Ride: 2004 325Ci vert
Originally Posted by Zell View Post
Unless I have good reason to replace something, I am going to use all my parts for their intended useful life: AKA, when they show signs of failure.
Don't ask me why, but I just read through this thread tonight, and Zell's statement reminded me of something I learned in my first career as a plant engineer. There are three modes of maintenance: Preventive maintenance, predictive maintenance, and run to failure.

Some components are okay to run to failure. Windsheild wipers come to mind. Failure is when they start streaking, not when the rubber starts to shred.

Brake pads are usually maintained by predictive maintenance by measuring the wear at various time intervals (like every time you have the wheels off the car) to predict when they need replacing. BMW has taken this a step further by installing proximity probes that warn us when the brakes need replacing.

Rotating parts such as water pumps are usually maintained by preventive replacement. This is true for pressure parts like radiators as well.

Predicitive maintenance is actually the lowest cost method. All of the components addressed in the E46Fanatics forum can be fitted with some type of sensor to indicate impending failure so that each of us can wait until our car throws a code to tell us something needs to be replaced. Vibration sensors can tell us when bearings are about to fail. Strain gauges can tell us when the expansion tank or other plastic parts are about to yeild (not to mention the subframe). Conductivity probes can tell us when to change the antifreeze.

The problem is that adding all of the sensors and transmitters required to do this would make these cars outrageously expensive.

For the E46, we don't have these sensors installed in the car and wired into the ECM. That leaves us two choices: run to failure or preventive maintenance.

A lot of posts seem to indicate waiting for some indication of impending failure of a water pump or whatever to replace a part. The challenge for these posters is having a reliable "indicator". Invariably, these people are relying on their own five senses as indicators. The problem with this is, when you are driving your car, you are not going to hear your bearing failing. Your "indicator" is in the front seat and tuned into the radio.

If you are relying on your five senses as indicators for predictive maintenance, you are more likey practicing "run to failure". Have at it and good luck.

Just don't join in the arguments about the correct intervals to perform preventive maintenance.

“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.”

Originally Posted by Mike Miller - BIMMER
I just don't know what I'd do with 560 hp that doesn't involve getting arrested.

Last edited by wildirish317; 12-02-2012 at 07:06 PM.
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