Finally got time to replace my precombustion chambers and seals this week. Reason for doing this was high temps getting to the red. I did go through troubleshooting process beforehand. Also did much research on the forum here. Checked belt tension, fan flow, radiator. The indicator that the precomps or gaskets/shims might be the problem was the soot or black color of the coolant along with bubbles when engine was running. Here are some observations , tips or just my 2 cents worth that may help someone else.
Of the four chambers one was pitted , the other three looked good. The shims were of different thicknesses probably to align the glow plugs in the "GO" range per the manual. Two of the shims were pitted bad therefore the shoulders were narrow. The edges of the seats in the head were pitted. Having ground valves and seats in engine heads in my younger days this is where I thought it would be good to have a cutter that could recut the seats a few thou and clean them up . There may be such a tool around , I don't know though.
Tools I would recommend are : 6 point sockets preferably impact style as they are usually thicker, pull handle for sockets, long cheater pipe for pull handle just in case, air impact, battery powered impact 3/8 drive (makes taking any covers off quicker), 1-1/2" diameter wire cup brush (fine or medium wire,definely not coarse)with 1/4" shank to use in drill, 6-8" long adapter with chuck to use brush in drill, cordless drill or other powered, good torque wrench, some fine grit sandpaper, blow gun or air nozzle, a vacuum of your choosing( I used a sand blasting gun with the pickup hose to suckout trash that would fall down in the hole). The brush is good for cleaning up the seat that the shim sets on and the sides of the hole the O-rings passes through. DO NoT use a sanding disk on the seat in the head where the shim seats. The fine grit sandpaper is good for cleaning up O-ring seat areas by finger tip. Also prior to final install leave the O-ring off the chamber and put the shim on it with a dab of grease to hold it there then screw in the chamber for a dry fit , this will show where your glow plug will end up and what thickness shim to use for the right position. For final install be sure to use a high temp Neversieze on threads.
If you are going to do this for first time, my advice is spend the time to research , get the proper parts manual and service manual for your machine. While this forum is great for searching for help and answers, someone's always happy to answer questions and give advice, it's great to have the manuals at hand. Mine were worth every dime I've spent on them. I'm no expert and definitely need help at times figuring something out.Lastly it does pay to check with CAT for parts and pricing. Found a couple of parts that were way lower than Ebay or internet and available the next day.
Dozer info: D4D78A1859 , D330 motor , all work done with head still on motor.
