You've just installed a new water pump, filled the coolant, and there's a drip behind the pulley. Do you tear it all apart again, or give it a chance to seal? That's where I left off in part 1 of the CAT 931 water pump replacement, with coolant dripping from my handmade gasket. Here's what I decided to do about the leaky seal on the CAT 931 Traxcavator, and what the gasket makers say about it.

After Some Research

In this video, I further explain the steps going into the water pump repair on the CAT 931.

After some research, I found that it is not uncommon for a gasket to leak for a brief time before it "cures." I read that if you get the engine up to temperature and run it for about thirty minutes, the gasket should have a chance to cure and the leaking should stop.

I found this information somewhat questionable, but I decided to give it a try. The next day, I went back to the machine and found it was no longer actively dripping coolant onto the engine. The gasket just appeared to be seeping some. I put the pulley and fan back on and re-tensioned the fan belt. I also checked that the coolant level was up, since part of me assumed the gasket had stopped dripping because there was nothing left in there to drip.

Start Your Engines

I started the engine and ran it for about twenty minutes, long enough for the water temperature gauge to enter the green area. I kept a close eye on the gauge to make sure it wasn't about to overheat. I moved from one side of the engine to the other watching the gasket, and after about ten minutes it did appear that the gasket was not leaking, or at least not dripping like it was.

At this point I decided to just monitor it, get the CAT back together, and maybe get some actual work out of the machine for a change. I put the hood back on, bolted the side engine covers back on, and it was time to go.

What Gasket Makers Actually Say About Seeps and Sealant

Here's what the gasket and pump sources say, for anyone facing the same seep.

Does a seep stop on its own? None of the gasket or pump sources checked for this article promise that a weeping coolant gasket will seal itself, and none describe a plain fiber gasket "curing." Curing applies to sealants: Fel-Pro notes RTV typically needs 24 hours for a full cure (Fel-Pro). The useful distinction is between a damp film that shrinks or stays the same over several heat cycles, which you can watch, and an active drip, which won't fix itself.

Is sealant appropriate? Fel-Pro's general guidance is that a gasket should be installed clean and dry, with RTV used only on corners or gaps where castings step, because "a little RTV goes a long way" (Fel-Pro). Fel-Pro also warns that RTV can extrude when the gasket is compressed and end up restricting or blocking an oil or coolant passage (Fel-Pro). For water pumps specifically, Know Your Parts says not to use silicone or other sealants that can block the weep hole (Know Your Parts). If your pump or service manual calls for a sealer, follow it. Otherwise, a correctly cut gasket on clean, flat surfaces is the fix, not more goop.

When should you redo the gasket? Plan on pulling it again if any of these are true:

  • It still drips, rather than leaving a damp film, after the engine has been through a few full warm-up and cool-down cycles.
  • The wet area keeps growing from one use to the next.
  • The coolant level keeps dropping when checked cold.
  • You can see a tear, a crease, or a spot where the gasket squeezed out near a bolt hole.

When you redo it, scrape both faces clean and flat, cut the new gasket from material meant for coolant (Fel-Pro, for example, sells a rubber-cellulose sheet for water pump and thermostat housings), and tighten the bolts evenly in a crisscross pattern. Don't crank them down to stop a leak. Over-tightening can split a fiber gasket at the bolt holes.

Getting Ready to Work

Now that the machine was back in running order, it was time to put it to work. I drove it to the edge of the property where the current cow pasture fence ends at an old logging path that is very uneven. I tried to scrape the bumps out with the bucket, but it didn't help, so I decided to put the rock rake on.

Removing the bucket clamp extension was much easier than putting it on, which was a relief. I set the clamp down along the edge of the path and moved on to the rock rake. This rake must weigh 800 lbs. It's very difficult to move and even more difficult to get in position to pop the pins in. After wrestling with it for a little over half an hour, I got it on and was ready to test it.

First Use with the Rock Rake

Watch me install and use the rock rake on the CAT 931 for the first time.

Assuming the proper way to use this rake is with the teeth about 6 inches below the bucket, I made the adjustments, put the bucket down to the ground, and away we went. The rake tore up the ground and pulled the rocks up as it was supposed to. I quickly found that the ground was still fairly wet, and there were a few spots where I was concerned about getting stuck.

I didn't expect the rake to be so good at tearing out roots. That was a nice surprise, as it ripped apart the topsoil from years of leaf decay. I made one pass along the path and turned around for a second. Afterward I hopped off to look at the ground, and it was in rough shape. I couldn't decide if it was better or worse than before I started. Either way, I was satisfied that I'd used the machine without it breaking, so it was a good point to call it a day while I was still ahead.

How to Keep Checking a Seeping Gasket

A seep that looks fine at idle can behave differently after real work. If you're in the same spot, these checks tell you whether it's holding:

  1. Look after the machine has worked under load, not just idled. That's the condition that counts.
  2. Check the coolant level cold, before each startup, never with a hot cap on a pressurized system (NAPA). A level that holds steady is the best sign.
  3. Watch the temperature gauge while working. It should stay in its normal range.
  4. Wipe the flange dry after a job, then look again after the next one. A dry flange means it's sealed. Fresh wetness tells you it's still weeping.
  5. Check the ground under the machine where it's parked overnight.

Summary

After using the machine for about an hour, I checked under the hood to see if the gasket was still leaking. It looked the same as when I started, so I was pleased. I then walked the path to see what kind of mess I'd created, and found some large rocks just under the surface that will need to be pulled out with the backhoe. Once the bigger rocks are moved, a couple of passes with the tractor rake might be all that's needed to get the path flat.

If the machine will sit for a while between jobs like this one, a battery maintainer keeps it ready to start.

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.