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Expert Advice: May / June Edition

Questions and answers from the Truck Trend Garage!

Alex Steele
Jul 4, 2007
Q: I have a 2000 Ford F-150. Its A/C works perfectly, but the heater doesn't--all it does is blow out cold air. What could be the wrong? For each possible problem, what would the estimated cost of repair be?
Photo 2/4   |   expert Advice
A: When dealing with a no-heat condition, first check the coolant level. Even before an engine begins to overheat, the coolant level can be low enough to limit flow through the heater core. Also take a close look at the coolant-temperature gauge. A high or erratic reading may indicate air in the system or another coolant-system problem. A continuously low reading is a sign the thermostat is stuck open. This will prevent the engine from reaching normal operating temperature and, at the same time, limit or eliminate warm air at your feet. Some systems use a hot water valve to shut off coolant flow through the heater core during A/C operation. And poor coolant-system maintenance will eventually hamper heater performance by clogging up the heater core with grunge. On the dry side of the heat system are temperature-control components. Air-conditioning and heater-output temperatures are controlled by a door that blends the warm air from the heater core and the cool air from the air-conditioner's evaporator. The temperature knob on the control panel (or other means when dealing with a climate-control system) signals an electric-powered actuator (motor) to move the blend door to its proper position. There are too many possible causes to list with prices, but topping off the coolant is a cheap place to start.
Cadillac Conundrum
Q: When I tried to start my 2000 Escalade, it wouldn't turn over. Even though it cranks, I tried hooking up jumper cables. I also tried flooring the throttle in case it was flooded, but it still didn't start. There was no fuel smell (it had half a tank of gas) and no symptoms prior to this. My guess is it's the fuel pump, but I hope I'm wrong. Is there something else to check?
A: A technician would start on one of two diagnostic paths: (1) plug in a scan tool and check for trouble codes and obvious signs of incorrect data, or (2) do a quick check for spark at the spark plugs and fuel pressure from the fuel pump. If both look okay, he'd test for a good signal from the powertrain control module to the fuel injectors. (The PCM powers up the injectors so they can shoot fuel into the combustion chambers.) If nothing showed up by that point, he'd probably pull a spark plug or two to see if they were washed out by fuel, while keeping an eye out for any signs of internal engine damage. If there were a loss of spark and signal to the injectors, that might indicate a failure by a vital component such as the crankshaft position sensor. The crank sensor is what tells the system when the engine is rotating, and if so, how fast. Without that signal, there's nothing to trigger a spark or a fuel-injector pulse. Regarding the fuel pump: If there was little or no fuel pressure, you'd inspect the fuel regulator, filter, lines, and all applicable circuitry before condemning and replacing the pump. If it boils down to fuel-pump replacement, it's a good idea to mention Cadillac Technical Service Bulletin 04-06-04-088b to the technician doing the job. It describes an issue with a defective connector on top of the fuel-pump module, which is sunken into the fuel tank. This poor connection has caused repeat system failures, so the connector should be replaced with a modified unit, along with the fuel pump, on vehicles specifically listed in the bulletin.
BMW Dead Battery
Q: Two weeks ago, the battery in my 2002 BMW X5 died while parked in the garage overnight. I knew I hadn't left anything on, and the car was jumped and worked fine. The next day, it happened again--no radio, no lights, nothing.
This time it wouldn't even take a jump. I had it towed to an auto shop--even though I had recently put in a new battery, the shop replaced it anyway and assured me they found nothing wrong with the electrical system. I went to pick it up, and it wouldn't start again. They tested the car again and said it must have gotten run down from sitting in the sun (for a day?). I went to pick it up again, and it still wouldn't start. Now the shop is telling me they don't have a way to diagnose what's draining the battery. They just have to monitor it. In this day and age, is the only way to find out what's wrong by watching what kicks on? This auto shop isn't a BMW dealership but is authorized by BMW.
Photo 3/4   |   expert Advice
A: I'm not sure about being "BMW authorized" outside of the Bimmer service department. But I am confident a good battery won't go dead spending a day in the sun. It's got to be one of two things. Either they don't know how to correctly test for a parasitic amperage draw on the battery or it's an intermittent problem, which doesn't show up while testing. That the battery is out of commission every time you try to pick up the vehicle has me favoring curtain number one. A parasitic drain is simply current being used from the battery with the ignition off, doors closed, lights out, etc. This is necessary to keep your clock right and FM presets intact, among other things. It's considered normal when the amperage draw stays below a certain limit--in your case, 40 milliamps. Get it to a BMW service department before you pull your hair out. The correct test procedures are somewhat complex requiring special tools, and there are a few relevant issues pertaining to your X5. There have been notable parasitic draw problems from iPods and cell-phones, along with an on-board control-unit failure, which can be difficult to diagnose.
Dinghy Towing Honda
Q: I recently purchased a 1998 Honda Passport 4WD to use as a dinghy tow vehicle behind my RV. The owner's manual states I have to remove the front and rear driveshafts prior to towing. A local mechanic who runs a towing service told me it would be all right to tow this vehicle with the transfer case and automatic transmission in neutral, as long as I stop every 200 miles or so to run the transmission through the gears for lubrication. Can you can clarify this?
Photo 4/4   |   expert Advice
A: Vehicle drivetrains vary in their reactions to being towed. The danger comes from a lack of lubrication within the transmission. While dinghy towing (four wheels on the ground), the transmission's internal gears are turning, similar to normal driving; however, when the engine isn't running, there's nothing powering the hydraulic pump, which circulates the transmission fluid and lubricates internal components. This results in excess friction, heat, and damage. Some manufacturers offer detailed instructions that allow for dinghy towing under specific speed and distance limitations, as your mechanic suggests. But that doesn't seem to be the case with your Passport (which is basically just a rebadged Isuzu Rodeo). If Honda and Isuzu are telling you it'll cause damage, remove the driveshafts, or else. The safest course of action is to use a trailer and keep it off the road altogether--or remove the driveshafts, which I'm sure will get old quick. A third alternative is a "driveshaft coupling" made by Remco (www.remcotowing.com). With the coupling installed, you can disengage and engage the rear driveshaft with the pull and push of a control cable routed under the driver's seat. This allows the rear axle to free-wheel without rotating the driveshaft and transmission. Remco's 1998 Passport kit will run you $450 to $800, with or without a complete modified driveshaft. Remco tech support claims that removal of the front driveshaft will not be necessary as long as the transfer case is kept in neutral.
More Power for Expeditions
Q: My 1999 Ford Expedition has the 5.4-liter engine and 103,000 miles. It's only used for hunting and fishing, often pulling a trailer. The engine's a bit short on power with even a medium trailer and often downshifts to second gear at 70 mph. Overdrive is almost out of the question. Even reducing speed is of little help. Of course, fuel use is extreme. Would a custom lower-restriction exhaust and a programmable chip help? Is chip programming safe for the engine?
A: I don't know how heavy your "medium" trailer is, but 70 mph in second gear isn't a good place to be, regardless. There are lots of aftermarket exhaust systems, intake ductwork, filters, and control-module programming alternatives, and they all illustrate impressive before and after performance graphs. But installing the products and then adding up the promised horsepower and torque with a calculator rarely agrees with the dynamometer. A 1999 Expedition with over 100,000 miles on the clock used for hunting and fishing may not be the best place to invest in performance parts, which may end up disappointing you. With 260 horsepower pushing a heavy full-size SUV, Ford's 5.4-liter V-8 was no Hercules to begin with. It was revived in 2005 with a 40-horse boost thanks to new three-valve cylinder heads. Have the sport/utility gone over from head to toe. Maybe there's a mechanical issue slowing you down, such as an obstructed catalytic converter, transmission problems, or inadequate fuel delivery. A dirty mass airflow sensor also can produce some strange symptoms.
Bad Suburban Vibrations
Q: My 1998 Chevy Suburban has a vibration that feels like the U-joints are bad. I've had the driveshaft balanced, installed new U-joints, rebuilt the front end, replaced the tires, checked and balanced the wheels, and tried new wheels. Besides having paid a fortune for all these unsuccessful fixes, I've paid a fair amount for wrong diagnoses as well. I bought it used with 70,000 miles. It now has 130,000 and the problem has always been there.
A: Typically, you can narrow the source of a vibration to the driveline if the vibration disappears after shifting the transmission into neutral at speed. Also, that the vibration is most notable during acceleration tends to indicate the driveline. One item you didn't mention, which can produce a driveline vibration, is the ride (trim) height being out of whack. There are specifications for your Suburban requiring measurements taken from exact points at the suspension and frame. This is to determine that the vehicle's suspension is holding the chassis at an optimal height off the ground (front and rear). When the ride height is correct, the suspension and driveline will sit at their most efficient positions. If the height is incorrect, the driveshaft can be situated at excessive angles in relation to the transmission and/or rear axle. This will result in a driveline vibration, or a wobbly feel while giving it gas. Ride height out of specs can be caused by weak or broken springs, misadjusted front torsion bars, or damage from a collision. You also want to be sure the driveline is in a straight line and not knocked out of position from side to side--again, possibly from chassis damage. Additionally, there may be a broken transmission or engine mount, loose crossmember, transmission not bolted securely to the engine, and so forth.
To Premium or Not To Premium
Q: I want to buy an FJ Cruiser but it calls for premium fuel. This is an issue for me, as premium fuel is 25 cents more per gallon than regular. Can this vehicle run on regular gas, or can it be tuned to run on regular gas?
A: The 2007 FJ Cruiser is the same basic platform as Toyota's 4Runner SUV, and both use the very same 4.0-liter V-6 engine. So why does the 4Runner owner's manual stipulate a minimum of 87 octane (regular gas) while FJ specifications read 91 or better? Good question. According to David Lee, product education administrator at the University of Toyota, Toyota wanted the new FJ Cruiser to meet the more stringent LEV II (Low-Emission Vehicle) standards, which it was able to achieve, but only while running its V-6 on a 91 octane or higher-rated fuel. Therefore, in order to be officially deemed an LEV II vehicle, 91 octane had to be listed as the required minimum. The good news: you can run the FJ on regular gas without any significant ill effects (spark knock, loss of power), just like the V-6 4Runner (LEV I). The only differences will be a tiny bit increased emissions and an iota less power. On the dynamometer, the higher octane increases engine output by six horsepower and 10 pound-feet of torque at peak rpm, but I don't see that being perceptible in real-world driving.
Big Rims Mean Hot Brakes?
Q: I changed the rims on my F-150 from 17- to 2--inch. Do I need to upgrade the rotors and calipers to match? If so, what size? I was told that due to the changes I made to my rims' size, the brakes are now getting hot and squeaking when I apply the brakes. Is this true?
A: Wheel size shouldn't have a significant effect on the brakes. If you're upsizing the wheels while compensating with tire size to maintain the original tire diameter/circumference, there should be limited effect on drivetrain performance or speedometer calibration, too. But ride and handling is another story. The only other issues would be if the aftermarket wheels are significantly heavier than the originals, if you switched from alloy to steel wheels (alloy disburses heat better), or if there's a problem with airflow through the wheels needed for brake cooling. Not everyone realizes how the aerodynamics of wheels direct airflow to the brakes, especially disc brakes. That's why a few vehicles even have left- and right-side wheels. Installing a left wheel on the right side will reverse the designed inward path of air and potentially cause a brake overheat condition. I've also seen aftermarket shields mounted behind wheels to confine brake dust. It may keep your wheels clean, but it also cuts off the airflow and cooks the brakes. If the wheels were confirmed to be causing the problem, I'd get rid of them before upgrading the brakes. Of course, the squeak in your brakes may be totally unrelated to the wheels. If you're unsure of a diagnosis, get a second opinion.
How To Reach Alex
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage--visit Alex Steele at www.RealWorldAutomotive.com.

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