That ‘bowling ball’ sound may be your fuel tank

Dear Mike: I have a 2003 Dodge Durango. It feels as if there is a bowling ball loose in the cargo compartment, rolling around on a carpeted surface.

This happens under acceleration from a stop, and only when there is about three-quarters of a tank of gas — not when the tank is full. I’ve checked the suspension and tightened down the spare tire.

I was unable to replicate the noise for a mechanic.

— C.H., via e-mail

A: This clunk seems to be different from the clank caused by driveshaft spline play on many rear-drive vehicles, because it happens, according to your original letter, after the vehicle has moved a few feet, and the noise also seems to be sensitive to the rate of acceleration. I’ll assume that a good mechanic has already looked at all the dangly bits in your rear suspension.

I think it might be your fuel tank. The lack of noise when the tank is brimful is the tip-off. There’s a loose baffle or an overly flexible spot on the tank, like the bottom of an old-fashioned oil can. This may be the result of a large, shallow dent in the tank.

The fuel sloshing back and forth at initial acceleration causes the loose baffle to move far enough to hit something metal-to-metal. Or perhaps the “oil-canning” spot has enough weight and moving mass put onto it to become unstable. Either way, when the tank is full, there’s no slosh and therefore no movement.

The danger is that the baffle will break loose and damage your fuel pump, which is inside the tank. The only cure for that would be a new tank. A mechanic may be able to repair an oil-canned tank, however, by removing it and carefully inflating it to blow out the dent.

Your truck should be under warranty. I’d be sure to get a repair order that documents your complaint ASAP, so that you can prove that you’ve pointed this out to the service department.

Dear Mike: My cats like to sit on the roof of my Sebring Convertible and look around the yard. The problem is that they shed, and periodically the hair plugs up the drainage holes from the convertible top. Then I get water in the interior on the driver’s side.

The owner’s manual says to keep these open, but not how to do it. The dealership will clean these drain holes, at some expense, but won’t tell me how.

— R., via e-mail

A: I usually use compressed air to blow out loose stuff like this. I bet the dealership is doing exactly that.

If you don’t have a compressor, that’s not an option, although you may be able to use one of those cans of air intended for cleaning cameras and computers. If you need to do this on a regular basis, however, a shop vacuum or canister vacuum with a crevice tool might do the job better.

Dear Mike: I’m trying to find out how to free up an engine that has not run for almost 20 years.

— D.B., via e-mail

A: I’m assuming that the engine won’t turn at all.

If that’s the case, start by removing the spark plugs and pouring 2 tablespoons — no more — of Marvel Mystery Oil, obtainable at any auto-parts store, into the plug holes. Reinstall the plugs, and wait a week for the oil to dissolve some of the gelled oil on the cylinder walls.

If this isn’t enough to let the starter motor break the crank free, try a big breaker handle on a socket on the crankshaft. I’ve also used a pry bar on the teeth of the flywheel’s starter ring gear.

Now that you’ve got the thing turning, getting it to start raises another raft of issues. Change the oil and oil filter. Drain the fuel and refill with fresh gasoline. Replace the fuel filter. Rebuild the carburetor, or remove and bench-clean the fuel injectors. Replace the points, plugs, rotor, ignition wires and condenser. The old fuel still in the lines won’t burn well, so you may need a quick shot of spray carb cleaner to get enough volatiles to ignite. Don’t use ether.

Once you tease the thing to life, change the oil and filter again within the first 100 miles or so. Be prepared for an engine that leaks oil from dried-out seals and gaskets, burns oil and has low compression owing to rusty cylinder walls and valve seats. And expect to replace the hoses and belts within a month or two, because the 20-year-old rubber won’t last long.