COMPRESSOR GP-REFRIGERANT 3729493 - Caterpillar

4C8753 Extended Collect
A new 4C8753 Extended Collet is available to increase the accuracy of fuel setting measurement and adjustment on the 3500 Family of Engines. It is designed to be used with the 8T1002 Electronic Position Indicator Probe or a dial indicator. This extended collet prevents side loading of the probe shaft by the fuel stop lever in the governor. This side loading can cause setting errors and breakage of the contact point on the indicator. The extended collet attaches to the indicator probe or dial indicator and is the correct length for use with the 5P7263 Contact Point specified in the fuel testing and adjusting instructions for 3500 Engines. Instructions for using the 4C8753 Extended Collet are included in Special Instruction SEHS9278 which is packaged with it. This collet is being added to the 6V7880 Timing and Fuel Setting Tool Group.
Illustration 1. 4C8753 Extended Collet.Problems With Electronic Position Indicator Probe
Several problems have been reported with the 8T1002 Probe, which is used with the 8T1000 Electronic Position Indicator. Following are the solutions to these problems.
Probe Tip Cannot Be Easily Changed
Loctite® was installed on the threads of some of the tips on the 8T1002 Probe. This makes the tip difficult to remove. If the probe tip is heated, the Loctite will break down and the tip can easily be removed for changing. Use a heat gun to heat the tip to a maximum of 269°C (550°F). While still warm, protect the shaft with a cloth, and use a pliers to hold the shaft while removing the tip. A No. 4-48 tap can be used to clean the threads after removing the tip.
Probe Shaft Not Counterbored
The threaded hole in the end is not counterbored on some probe shafts. This can cause interference resulting in a broken tip if the tip does not have enough threads to allow it to seat correctly. If counterbore (A) is missing, it can be easily added with these instructions. To identify if the shaft is correctly counterbored, see Illustration 2. If the threads extend out to the end of the probe shaft, the counterbore is missing and must be added.
To counterbore the probe shaft, use a 3.2 mm [No. 30 (.128")] drill in a drill press. Hold the probe shaft in the vertical position with a bench vise. Drill the end of the shaft 1.5 mm (.06") deep. After drilling use a No. 4-48 tap to clean out the threads. When a tip is installed, there should be no air gap between the ends of the shaft and the tip.
Illustration 2. Location of counterbore in probe shaft.