Tracking Down the Smell
Q: I have a 1999 Suburban, and my wife noticed that the cargo area's carpet is wet. I'm not sure if it's leaking around the gasket on the door or if it's coming from the rear A/C. Is there a rear heater core? The moisture is starting to create slime and a bad smell.

A: The auxiliary heat/air-conditioning system incorporates its own heater core and evaporator in the rear of the vehicle. The coolant and refrigerant hoses are routed from the engine and the A/C compressor up front. And, yes, just like in the front, a plugged-up evaporator drain may cause an overflow of condensation into the truck. On the other hand, similar Suburbans have had problems with rainwater intrusion in the rear compartment. Your local Chevy dealer should have a copy of Technical Service Bulletin Number 00-08-66-001. This TSB gives a detailed procedure for installing a new rear-entry weatherstrip and properly adjusting the rear doors or endgate. This isn't the type of job you want to do twice--never seal anything prior to pulling up the carpet and inspecting for leaks while thoroughly hosing down the vehicle from the outside. Also, let the A/C run to be sure condensation is flowing freely from the evaporator drain to the street. When repairs are complete, always water-test one last time to confirm the fix. Then replace all of the carpet's padding/insulation, thoroughly dry the carpet and floor, and clean and disinfect everything to prevent a recurrence of any mildew odor.

Diesel Fuel Economy
Q :I purchased a 2002 Ford Super Duty F-350 Crew Cab with the 7.3-liter diesel engine and automatic transmission. My family loves this truck for daily use and when we pull our 32-foot Jayco fifth wheel on vacation. The bargaining chip in my purchase was the terrific mileage diesels are supposed to get. This is where we get to my issue: Almost every Super Duty diesel owner I've talked to has reported mileage in the 15-23-mpg range. When it was new, I was getting about 17 mpg and expected it to increase as the motor broke in, but the opposite has happened. My mileage has dropped little by little each time I pull my trailer. I'm now getting 11 mpg on average. I've been to the dealer--where I purchased my truck--multiple times and the diagnostic scanner hasn't shown any fault codes. The dealer blamed everything from the fuel and air filters (replaced), the engine oil used, and the blends of winter/summer fuels, and has implied that everyone I've spoken to hasn't been entirely truthful about the mileage. I don't want to wait until my warranty is up to find out I need a new set of injectors or, worse, that the motor needs to be replaced.

A: The Environmental Protection Agency doesn't require manufacturers to post fuel-economy estimates on trucks above 8500 pounds that are GVW-classified as heavy-duty. This lack of a uniform standard leaves us on our own to figure it out. Hopefully, the technicians evaluating the problem are correct in determining the engine, transmission, and all surrounding systems are in the clear. If it's been the same technician at the same service department each time, take it to another dealership and ask for the shop foreman or a top diagnostician to check it out. Always hold on to the paperwork. If you have the complaint documented while under warranty, you'll have a strong case if the truck is diagnosed later. Fuel-mileage estimates are just that, estimates. There are so many variables that odds are slim for any two vehicles with two different drivers, on two different roadways, to produce exactly the same numbers. Towing, hauling, and high-speed driving are going to considerably affect your fuel efficiency. It sounds like you were referring to fuel economy while towing, so here are a couple of comparative examples. Gale Banks Engineering did some before/after testing on a 2001 F-350 with the Power Stroke 7.3-liter turbodiesel. Before the addition of several performance enhancements, the stock truck averaged 12.89 mpg pulling a 10,000-pound trailer over variable roadways and averaging about 60 mph. (You can log on to www.bankspower.com for more details.) The fuel economy was up to 13.14 mpg after making changes to the intake, exhaust, transmission, and fuel calibration. Our own Truck Trend personnel have come up with an average of about 13.5 mpg on a 2004-model Super Duty one-ton dualie with the 6.0-liter Power Stroke engine and five-speed automatic transmission, pulling an 8000-pound boat (September/October 2004). Unloaded, the same truck on the same route, with the same driver, came in just under 17 mpg.