Expert Advice, October 2002 edition

2001 Nissan Frontier 4x4 needs supercharged diagnosis
Q: I own an 2001 Nissan Frontier 4x4 with the supercharger and 50,000 miles on it. I brought it to the dealer for an oil change, and while driving to work I heard a clanking sound coming from the engine. I opened the hood and noticed the antifreeze overflow was bone-dry, so I brought it back to the dealer; the mechanic said the noise was from the supercharger, and when it warms up it will go away. Even when the truck is warmed up I still hear the noise when stopped at a light. Is this common for a supercharger or is the dealer pulling my leg?

A: The Frontier pickup with the supercharged 3.3L V-6 has been out for only a few years in a small volume of production, so all reliability issues involving the supercharger may have not yet come to the surface. I've asked several members of various Nissan service departments what sorts of complaints they've received involving the forced-induction Nissan, and there seem to have been very few at this time. It's true that some superchargers will normally emit a rattling type noise at idle. But the new Frontier SC I road tested when they first came out was fairly quiet, aside from the normal supercharger whine on acceleration. The Nissan 3.3L engines have an inherent lifter clatter on cold startup that disappears once oil pressure reaches the hydraulic valve lifters; this should be considered normal. I mention this in case it's part of the noise you're getting on startup. The technician changing your oil shouldn't have let you go with an empty coolant reservoir. Your best bet is to take it back to the service department in order to reevaluate the noise and perhaps compare to another supercharged Frontier. At this point, a noticeable noise at idle when hot does warrant further investigation.

Excess 1997 Ford Ranger Drip
Q: My 1997 Ford Ranger has been having a problem in high-humidity weather: Condensation is dripping on the passenger-side floor when the A/C is on. I brought it to my mechanic, and he thought the evaporator drain must be clogged. He said that he blew compressed air through it and it should be clear, but I still have the problem and the condensation is also dripping out under the truck just like it's supposed to.

A: Ford has come out with a Technical Service Bulletin pertaining to this problem and there is a fix for this misrouted condensation condition. As we know, a large amount of water condenses from the humid air as it passes through the cold evaporator core part of the A/C system within the dash. The water then drips off the evaporator and into the bottom of the plastic evaporator housing. From there, it makes its way to the street via the evaporator drain tube that passes through the firewall. The problem in some 1997-1998 Rangers, Explorers, and Mountaineers, along with the 1999 Super Duty trucks, is a leakage of moisture-rich air around, and not through, the evaporator core. This air delivers condensation further into the heater plenum and duct work, which is not designed to drain off the condensed liquid. That's why water ends up on your passenger's feet. The recommended repair is a decent size job that involves the removal of the evaporator and a detailed positioning of a new evaporator seal. This is to make certain that all incoming air must pass through the cooling fins of the evaporator core while leaving no pathway for air to bypass the core and reach the heater plenum. The Ford dealer can help you out, and it may be expensive if you don't have an extended warranty.

2001 Silverado 2500 4x4 wants more power
Q: I own an 2001 Silverado 2500 4x4 with extended cab and 3.73:1 rearend. It's rated at 300 hp and 360 lb-ft of torque. While my truck has great power and performance, I note other GM models have this engine with higher power ratings (Sierra C3: 325 hp; Yukon Denali: 320 hp; and Escalade: 345 hp). Can you identify what GM has done to increase the power for these versions of the Vortec 6000 engine? I tow a 29-ft fifth-wheel trailer weighing 7700 lb, and while my truck seems to handle the job well, I wonder if there are some simple and relatively inexpensive things I can do to increase its power?

A: All the vehicles you've mentioned, with the exception of the Cadillac Escalade, utilize the Vortec 6000 LQ4 V-8 engine. The Caddy SUV is actually fitted with the Vortec HO 6000, option code LQ9, and uses a higher compression ratio, via a piston upgrade, which brings it up from the LQ4s 9.4:1 to a 10.0:1 ratio. This explains the significantly higher power rating of 345 hp at 5000 rpm. The Vortec LQ4 engines in the other 1/2-ton GM light-duty trucks, such as the Sierra and the Yukon, only have a slight horsepower variance. The plus or minus five horsepower is due to the different exhaust systems and air intake configurations in each model. Now here comes the tricky part. Your Silverado 2500 is considered a heavy-duty truck due to vehicle weight and therefore falls under certain federal regulations, one of them being the Transportation Equipment Noise Emission Controls. There was a problem with the Chevy and GMC 3/4- and 1-ton trucks equipped with the 6.0L V-8 engine producing excessive noise. Your truck's LQ4 engine actually had its potential horsepower downgraded. It now peaks at 300 hp at 4400 rpm because it was too noisy and would have failed the test pushing more horsepower at a higher rpm. According to the General Motors Engineering Communications Department, there were also driveability concerns involved with the decision, and the downgrade was accomplished through various means including the programming of the powertrain control module. One of the experts in GM performance reprogramming is Fastchip. You can log-on at www.fastchip.com or give them a call at 918/446-3019 for further details. You can pick up the K&N Generation II Fuel Injection Performance Kit to aid intake airflow for a few more horses. I also suggest not putting any money toward exhaust modifications on the 2500 series. The factory setup appears to have a good flow, and aftermarket performance systems are showing little or no advance in power.