The first sign was a smell. I came out of the house Thursday morning at quarter to six, and standing next to the Silverado in the driveway I picked up something sweet, almost like pancake syrup. That's coolant. Under the front of the truck there was a spot on the concrete about the size of a coffee lid, bright orange, which is the color of the coolant GM uses.
The odometer read 136,982. I checked the overflow tank, which was below the cold line, and topped it up to the mark with premixed coolant I keep on the garage shelf. Then I drove to work and watched the temperature gauge like it owed me money.
On a normal commute the gauge sits right in the middle and doesn't budge. Thursday it was fine. Friday afternoon, sitting in traffic on the Belt Highway in 96-degree heat with the AC running, I watched the needle creep a little past where it usually sits. It came back down once I was moving, but it moved, and on a truck that has never moved that needle in six years, that's a message.
That evening I put a flashlight on the front of the engine. The water pump on the 5.3 sits on the front, driven by the belt. There's a small hole on the pump called a weep hole, and when the seal inside starts to fail, coolant seeps out of it. There was a crusty orange trail running down from it and a fresh drip hanging off the bottom. I'm not a mechanic, but that one was easy to read.
One thing I didn't do: open the radiator cap or the overflow cap while the engine was hot. A cooling system is under pressure when it's warm, and hot coolant will burn you badly. Wait until it's cool to the touch. Always.
Why I didn't do it myself
I watched two videos about the job. The pump itself is held on with a handful of bolts, and plenty of people do it in the driveway. I still called our shop Friday night and got on the schedule for Saturday morning, August 2. Here's why.
The cooling system on a V8 is on my short list of jobs I pay for. Draining and refilling it properly matters, getting the air out of it matters, and if I get it wrong, the cost isn't a do-over. The cost is an overheated engine, and a warped head on this truck means the truck is done. It's also my only way to work. If I'm stuck halfway through on a Sunday night with a part that doesn't fit, I'm calling Andre or Tina at 5:45 Monday morning, and neither of them would thank me.
The shop checked the system with a pressure tester to confirm it was the pump and not a hose or the radiator, then replaced it the same day.
The bill, line by line
- Water pump with gasket: $198
- Coolant, two gallons: $48
- Labor, 2.6 hours at $125: $325
- Shop supplies and coolant disposal: $22
- Sales tax on parts: $19
Total: $612. I'd guessed $700 in my head, so I walked out feeling better than I'd planned to.
The service writer asked if I wanted the thermostat done at the same time for about another $90. I asked him if mine showed any problem. He said no, it was just a "while you're in there" option. I said no thanks. I may regret that someday, but I'm not going to replace parts that are working because they happen to be nearby. If it fails, I'll know exactly where it is.
What it comes to
I bought this truck in 2019 at 74,000 miles. The original pump lasted to 137,000, which is about what people say to expect on these engines. If the new one makes it another 60,000 miles, that's about a penny a mile. That's the kind of number that lets me sleep.
The gauge sat dead center all the way home from the shop, and it was still sitting there Monday morning on US-36. I checked under the truck every morning that week anyway. Rusty came out with me each time and sniffed the spot where the drip used to be, which I choose to read as quality control.
It's in the notebook: August 2, 137,000 miles, water pump, $612. Second big bill of the summer after the van's air conditioning. I'd like there not to be a third.