BOLT 4T0521 - Caterpillar

Caterpillar Machines Equipped With Radial Seal Air Filter ElementsThere continues to be reports of users who have installed an axial seal style primary air filter element with a radial seal secondary air filter element. To fully understand this problem, remember on our earth moving equipment, there are usually two filters used per air filter canister.
Air first passes through the large outer filter, called the "Primary" element. The "Primary" element is designed to provide a minimum of 99.5% efficiency and yet provide sufficient capacity to require a normal service interval. There are some applications, such as operating in coal, sand, light powder dust and others, that may require more frequent servicing.
The inner element is called the "Secondary" element. The "Secondary" element provides protection against dirt entry while servicing the "Primary" element or if the "Primary" element is damaged. For these reasons, the "Secondary" element is sometimes referred to as the safety element. Since the "Secondary" element does not provide the primary filtering of the engine air and capacity is much less than the "Primary" element, the filter media must be less dense so excessive restriction to air flow does not occur. The "Secondary" element media has an efficiency of 96.0% in removing SAE fine dust.
The filter medial used in the radial seal air filters is the same filter media used in axial seal filters. However, a slight increase in air restriction may be seen because of the thicker flexible urethane sealing-ends of the radial seal filters. This increase is no cause for concern.
If the Caterpillar machines have factory installed radial seal air cleaner canisters, or if a retrofit sealing "ring" kit has been installed, radial seal air filter elements MUST be used. All radial seal air cleaner canisters and converted axial seal air cleaner canisters should have the 101-2850 Decal or 4P-6464 Decal (or its foreign language equivalent, see the chart) on the canister cover as a reminder that only radial seal elements are to be used in that canister.
101-2850 DecalThere have been no problems with users trying to install axial seal "Secondary" elements in radial seal canisters. The axial seal "Secondary" element will not fit in a radial seal canister because the axial seal "Secondary" element has a 6 or 8 bolt hole flange which gets in the way of the radial seal canister sealing ring.
The problem occurs when users install an axial seal "Primary" filter element in place of a radial seal "Primary" element. See the illustration for the difference between the sealing ends of the radial seal (top) and axial seal (bottom) "Primary" elements. The following are some of the problems that may occur:
* If an axial seal element is placed in the radial seal canister, the gasket seal contacts a curved surface that side loads the seal and may rip the seal from the filter end cap.* The axial seal element may be too long for the canister. This may cause the element to buckle and allow the expanded metal outer wrap to contact the