Truck Trend Garage: 2002 Dodge Ram 1500 Smoke Signal
Question: I have a four-wheel-drive 2002 Dodge Ram 1500 with the 5.9-liter engine. Ever since replacing the catalytic converter, I've seen white smoke coming from the exhaust. Is the new converter the reason for the smoke?
Answer: There's a basic rule of thumb for smoke from the tailpipe: Black smoke is excessive fuel (a rich condition), blue smoke is oil consumption, and white smoke is coolant being burned up in the combustion chamber. Excepions do occur, like some kind of internal residue burning off the inside of a new aftermarket catalytic converter. If that's the case, it should lessen and stop in a short period of time. Another possibility is normal moisture in the exhaust being vaporized. This condition varies, depending on climate and humidity. Also, if the white smoke is non-coolant steam, it will stop once the engine warms up. The most common cause of white smoke is a blown head gasket. Less common reasons include an internal coolant leak from the intake manifold, a cracked cylinder head, or even a cracked engine block.
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The first thing to do is check the coolant level. If it's significantly low, and there are no signs of an external leak, it's probably a head gasket. When the head gasket is compromised, there's no longer a perfect seal between the cylinder head and the engine block. When this occurs, coolant will be pushed or pulled into the combustion chamber from a passage that feeds coolant from the block to the head. There are a couple methods for testing, such as using an emissions analyzer probe in the coolant expansion tank to sniff for any amount of exhaust in the coolant.
The best method, though, is a cylinder leak-down test. A technician will bring each cylinder to top dead center of its compression stroke, one at a time. This is where the piston is all the way at the top of the cylinder bore, and the intake and exhaust valves are closed. At TDC, compressed air (about 150 psi) is fed into the cylinder with a special hose. This is when (with the radiator cap off, coolant level full) we watch for two things: the coolant level rising, and bubbles coming up in the radiator. Either situation tells us the compressed air is escaping the leaking head gasket (or a less common internal area) and into the cooling system.
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