Dear Jim,

I have a 1995 Ford E150 Econoline van (4.9L, L6) that was running fine until a few days ago, when I suddenly heard an ugly rumbling sound under the hood. It got worse while I drove, but I made it home.

After the van was parked for a while, I noticed quite a bit of water pooling underneath it, right in the middle, between the front tires. I'm not going anywhere until I know what the problem is. What does it sound like to you?

-- James Patterson

Those invisible workings under the hood can be mysterious, bro, but there's an easy explanation for this one.

Your water pump is falling apart, and you need to have it replaced immediately.

That's the final analysis, but here's the story of what really happened. There's a little bearing inside the water pump that popped loose while you were cruising along. In front of that bearing, there's a carbon seal that holds the water in the unit. The pump itself has some moving parts, including a shaft that goes up and down while the engine is running.

When that bearing comes loose, the shaft starts hitting the carbon seal, and it doesn't take long before the seal is destroyed -- that's what caused the rumbling, grinding sound you heard, and that's why water from the cooling system leaked out where you were parked.

If you're lucky, you'll just need to replace the water pump for a hundred bucks or so. But listen: Do not drive to the shop. Have the van towed.

That loose bearing can break off completely, which is very bad, because it's actually connected to the fan blades. If one of those blades then happens to break off at high speed, it can easily tear into your radiator, which means all the coolant gets dumped and your engine overheats in just a few seconds.

That's how it goes under the hood, brother. Things are moving fast, and if something starts knocking around loose in there, a little problem can become a big one in a flash.

Tip of the Week:

Transmission fluid holds up a lot longer than engine oil, drivers, but don't totally forget about it. It's still a type of oil, it breaks down over time, and the high heat that results is the number one killer of transmissions. Get the fluid and filter changed at least every 30,000 miles or so.

Buffalo Jim, owner of Allstate Auto & Marine Repair in Las Vegas, writes a weekly column. Send your automotive questions to him at buffalojim@lasvegasniftynickel.com. If Jim picks your question to answer in Nuts & Bolts, you'll also be the proud recipient of a deck of official Buffalo Jim playing cards, presented in a classy, tin box bearing his hairy image.