KIT-SEAL 1787189 - Caterpillar

The 5P3519 Piston Ring Gauge is used to check the amount of ring groove wear to see if pistons can be used again. The tool has six gauges, each machined to a specific thickness, and an information tag. The tag tells which gauge to use for different pistons, according to engine bore size. If the gauge can be fitted into the groove, the piston can not be used again.
A problem has been found on some pistons, where the gauge will "start" into the ring groove, but will not fit completely into the groove. For this reason, each gauge now has a mark across the gauge .025" .010" (0.64 0.25 mm) from the end. If the gauge fits into the groove beyond the mark, it is possible that the piston will not give normal service until the next overhaul.
If desired, similar marks can be added to earlier gauges. Use a depth micrometer or vernier caliper to find the correct location, then use a machinist's square and a hardened scribe to make the mark on each gauge.
During use of the gauge, do not use force to push the gauge into the piston ring groove.A correction has been made to the information tag with the tool. On earlier tags, opposite the 4.5" Bore-2 ring piston, gauge No. 1 was shown under "Intermediate Groove". These pistons do not have an "Intermediate Groove", and this indication to use the No. 1 Gauge was sometimes taken as an instruction to use the No. 1 Gauge in the oil ring groove. This was wrong because the gauge is not correct for this groove, and also because the oil ring groove does not need to be checked. On the new information tag, the word "NONE" is shown under "Intermediate Groove" for these pistons, as shown in the illustration. Earlier information tags can be changed, or a copy of the illustration can be fitted into the tag holder.