A loud pop, a squeal and smoke from under the hood. If that just happened on your crawler, look at the fan belt and water pump first. This is my write-up of replacing the water pump and belt on the CAT 931 Traxcavator: the steps I took, the issues I ran into, and what to check if you're doing the same job.

What Happened

Watch me explain how to replace a water pump in a CAT 931 Traxcavator Crawler

I was moving the CAT 931 out back into the woods to start thinning trees (not clear-cutting) and leveling the ground so we can plant grass and give the Highland cows a second pasture to rotate through.

While moving the machine, I heard a loud pop followed by squealing and smoke coming out from under the hood. I immediately shut it off. The belt looked mangled and the radiator fan looked bent, but the housing was full of smoke and it was hard to see, so I walked away and came back later.

The next day I found that not only was the belt mangled, the radiator fan was actually disconnected from the engine. I removed the fan guards, took off the belt and moved the fan out of the way enough to get a good look. The water pump's fan and pulley mount had broken off. It's held on by a single bolt, and that bolt had sheared.

Signs a Crawler Water Pump or Fan Belt Is Failing

Mine announced itself with a pop, but these are the usual warning signs:

  • Coolant leaking from the pump, one of the most common symptoms (NAPA Know How). A little dry residue at the weep hole can be normal, but that seep tends to become a drip as the seal fails (Know Your Parts).
  • Grinding or high-pitched squealing from the front of the engine (NAPA).
  • Play in the fan or pulley. With the engine off, grab the fan and rock it. Any wobble points to a worn pump bearing.
  • A temperature gauge that creeps higher than usual, especially under load.
  • A belt that squeals, looks shiny (glazed), or shows cracks or frayed edges.

Tear Down

At this point it was clear the water pump needed to be replaced. I put a pan under the machine and removed the pump. About 1.5 gallons of coolant came out. Having the old pump in hand was useful because I could visually compare it to the replacements I found online.

New Parts

I found a water pump on eBay and it arrived a few days later. The listing didn't mention a gasket, so I picked up some gasket material at AutoZone, and then found a gasket in the box after all. I also measured the width and length of the old belt and bought one on eBay. It wasn't the exact length, but it was close.

Back at the machine, I used the vent on the water pump as a reference, but the bolt holes didn't line up. I thought I had the wrong pump, but after rotating it a few positions I found the spot where the holes lined up. Unfortunately, the included gasket was paper, and after getting wet and being moved around, it ripped. Bummer.

So I turned to the gasket material I'd bought and made a new one. Back at the machine, I noticed a tear by one of the bolt holes and decided to make ANOTHER gasket. I made it very carefully so I wouldn't tear it, and installed that one.

Installing the Pulley and Radiator Fan

Installing the pump was easy. Getting the pulley and fan back on was a headache. A guard around the fan, which seems to funnel air through the radiator, was in the way, and I began to think I'd have to pull the radiator. After watching a video on removing the radiator, I realized that would be a big job. I took the hood off for better access from the top, saw how tight the radiator bolts were, got desperate, and decided to try removing just the fan guard.

The fan guard was held in by four bolts in a very tight spot. After some fighting I got them out and the guard was free. To my surprise, I had just enough room to get the pulley and fan onto the water pump mount and get the bolts in. Success!

Putting the Rest Back Together

With the fan tightened down, the fan guard went back first. Its four bolts sit in a space of about 3/4″, so I had to contort my hands into place, and I must have dropped the bolts thirty times. One bolt took me 45 minutes. You can imagine the relief when that was done.

I put the new belt on and used the alternator's adjustable bracket to tension it. You're supposed to have about 1/2″ to 1″ of play. Too tight puts extra wear on the bearings, and too loose lets the belt slip and squeal.

Next I put the hood back on and cleaned the radiator hose that connects to the water pump housing. It seemed to be in decent condition, so I was hopeful it wouldn't leak. There was also a mount on top of the radiator that I tried to remove, but I broke the bolts off. I put a new bolt in one side and left the broken one in place on the other because it was rusted in.

Then I added two gallons of coolant and started the engine. The hose I was worried about didn't leak, so it didn't need to be replaced. However, I noticed drips of coolant behind the fan pulley. They were coming from my handmade gasket. What a disappointment!

How to Check That a Water Pump Repair Held

  1. Watch the pump flange at idle. Use a flashlight behind the pulley, where my drip showed up, and keep hands and sleeves clear of the fan.
  2. Watch the temperature gauge. It should reach its normal range and stay there. If it keeps climbing, shut down and check coolant level and belt.
  3. Recheck the coolant level only after the engine has cooled. A hot, pressurized system can spray scalding coolant when the cap comes off (NAPA). Top off cold if the level dropped as trapped air worked out.
  4. Recheck belt tension after the first run, using the same play check you used at installation.
  5. Look again over the next few uses. Check the flange, hose and ground under the machine after each of the next several jobs. You want a dry flange after a few heat cycles.

Mistakes to Avoid

  • Running the engine dry, or adding cold coolant to a hot engine. Either can damage the seal, even on a new pump (Know Your Parts).
  • Smearing sealant around the pump. Know Your Parts says not to use silicone or other sealants that can block the weep hole. Part 2 covers what Fel-Pro says about sealant on gaskets.
  • Over-tightening the belt. It hastens bearing failure (Know Your Parts).
  • Reusing a torn or creased gasket. A tear by a bolt hole is a leak path, which is why I made another one.
  • Skipping the drain-and-flush. See my disclaimer below.

Now What?

Finding that leak was discouraging. My first thought was that I'd have to take everything apart and start over. Before jumping the gun, I decided to research what I did wrong, or a better way to install the gasket. What I decided is in CAT 931 Water Pump Replacement Part 2.

Disclaimer

I'm not a mechanic, that's for certain, and I know some of what I did wasn't ideal. For example, I should have drained all the coolant before starting. It's not recommended to just top off the coolant after removing cooling system parts, because dust and debris can get into the system and cause problems. I'll do a full flush once I know I don't have any leaks.

If your machine is going to sit while you wait for parts, keep its battery on a maintainer so it starts when the job is done.

Thanks for reading. I hope this was useful, and please come back to read what happens. Also, please subscribe to our YouTube channel. Lord willing, I'll be back with more videos.