In this article “CAT 931 Water Pump Replacement”, I will describe the process of replacing a water pump, belt and the reassembly of a CAT traxcavator crawler. I will talk about the steps I took and some of the issues I faced along the way.
Recently I was moving the CAT 931 out back into the woods in preparation for clearing out some trees in order to increase the available pasture land for the Highland cows. The plan is to thin out the trees (Not clear cut) and try to level out the land so its easier to plant some grass in the area for the cows to graze. If all goes to plan, this increased space will allow me to rotate the cows between the two pastures. Over time, we will expand these fenced in areas to all our property, but this will take time and work, so we are just focusing on one area at a time.
On this day, while moving the machine, I heard a loud pop followed by some squealing and smoke coming out from under the hood. I immediately turned off the machine to find the belt appears to be mangled inside the engine compartment and the radiator fan looks bent at the time. It was difficult to see because the housing was filled with smoke. So I walked away and intended to come back later to further investigate.
The next day, I revisited the machine to find that not only was the belt mangled, but the radiator fan was actually disconnected from the engine. I removed the fan guards and was able to get enough access to remove the belt and move the fan out of the way enough to get a good look and found the water pump fan and pulley mount had broken off. Its usually help on by a single bolt, but the bolt was sheared off.
At this point it became clear that the water pump needed to be replaced. Assuming that removing the water pump would result in some drainage of coolant, I put a pan under the machine to catch any drainage and removed the pump. About 1.5 gallons of coolant came out of the machine when the pump was removed. Having the water pump in hand was useful because I would visually compare it to the potential replacement products online when looking for a new one.
After finding a water pump on eBay, I ordered it and it was delivered a few days later. The description did not say it came with a gasket, so I picked up some gasket material at AutoZone. After opening the box, I was surprised to see a gasket was included. I also measured the width and length of the belt and purchased one on eBay. It wasn’t the exact length I needed, but it was close.
Once back at the machine, I used the vent on the water pump as a reference to put the new pump in, but the bolt holes did not line up. I immediately thought this meant that I had the wrong pump, but after rotating it a few positions, I found the correct spot and the holes lined up. Unfortunately, the gasket provided was a paper one and after getting wet and moving it around, it ripped. Bummer.
I then turned my attention to the gasket material I purchased and put a new one. After getting back to the machine, I realized that there was a tear by one of the bolt hole and I suspected that I should just make ANOTHER gasket. After making a new gasket and being very careful not to tear it, I brought it out to the machine and installed it.
Installing the Pulley and Radiator Fan
Installing the water pump was easy, but getting the pulley and fan back on was a headache. There was a guard around the fan that appears to be used to funnel the air through the radiator, rather that allow the air to escape from the sides. This guard was in the way and I could not fit the pulley and fan back in front of the water pump so i began to think my only option was to remove the radiator. After watching a video on removing the radiator, I realized this was going to be a big job. I started by removing the hood from the machine which gave me better access from the top, but after relaizing that the bolts that hold the radiator in place were in a tight spot, I got desperate and decided to try and remove just that fan guard.
The fan guard was held in with four bolts that are in a very tight spot. I was able to remove them with after some fighting and the guard was free! To my surprise, I had just enough room to get the pulley and fan on the water pump mount and was able to get the bolts in. Success!
Putting the rest back together
After tightening the fan back in place, it was time to get things put back together. The fan guard was the first task. There were four bolts that were in a space that was approximately 3/4″, so I had to contort my hands into place and I must have dropped the bolts thirty times trying to get them in place. One bolt in particular took me 45 minutes to get in place. You can imagine the sense of relief when that was done.
I then put the new belt in place and used the alternator’s adjustable bracket to tension the belt. You are supposed to tighten them to have about 1/2″ to 1″ play. Tensioning the belt too tight causes extra wear on the bearings and too loose causes the belt to slip and squeal.
Next, I put the hood back on and cleaned the radiator hose that was originally connected to the water pump housing. The hose seemed to be in decent condition so I was hopeful that it wouldn’t leak once coolant was added back to the machine. Also, there was a mount on top of the radiator that I attempted to remove but ended up just breaking the bolts off. I put a new bolt in one side, but ended up please the other one in place, even though it was broken, because it was rusted in place.
At this point, I added two gallons or coolant, and tested the engine. The machine fired up and I looked around for leaks. The hose that I was concerned about was not leaking, so i was pleased to see that did not need replaced. However, I noticed some drips of coolant behind the fan pulley. It was dripping from my handmade gasket. What a disappointment!
It was certainly discouraging to find this leak. My immediate thought was that I would need to take everything back apart and start over. Before jumping the gun, I decided I would do some research and see what I did wrong or try to find a better way to install the gasket before I start tearing things apart again.
I will do some research and make another attempt at the repair, I’ll come back with an explanation of what I did when I get there.
I’m not a mechanic, that’s for certain. I do know there are a few things I did that are not the ideal strategy. For example, I should have drained all the coolant before starting, its not recommended to just top off the coolant after removing cooling system parts because dust and debris can make it into the system and cause problems. I will do a full flush once i know I don’t have any leaks.
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