How do you check for wear on the main bearings in a Diesel truck?

Checking for wear on the main bearings in a Diesel truck is effectively performed using a plastic gauge. This method involves inserting a strand of plastic gauge between the bearing and the journal, then tightening the bearing cap to crush the plastic to a specific thickness. After this, the plastic gauge is removed and measured to determine the gap between the bearing and journal.

Using plastic gauge is particularly advantageous because it provides a direct and accurate measurement of the bearing clearance, which is critical for ensuring proper engine function. This method allows for a visual comparison against a calibrated scale that indicates the acceptable limits of wear.

Other methods, while useful in different contexts, do not provide the same level of precision for measuring bearing wear. For example, a feeler gauge may be utilized in various applications to measure gaps, but it lacks the specificity needed for evaluating main bearing wear directly. A taper gauge is typically used for measuring internal diameters or the taper of a surface rather than bearing clearance. Side play measurements can offer insights into other areas of wear like connecting rod bearings but do not specifically assess the main bearing tolerances.