Clutch Play
I'm having hot and cold problems with my '97 Ford F-150 XLT extended cab pickup. The truck is a two-wheel-drive model with the 5.4L V-8 and automatic transmission. My main problem has to do with apparent overheating and poor air-conditioner function. The secondary problem has to do with cold air coming out when the heater is on. The truck has approximately 125,000 miles on it. After I started noticing the overheating problem, I also noticed coolant on the garage floor.The radiator was worn out, so I installed a new one. I also replaced the upper and lower radiator hoses. That stopped the leaks, but the temp gauge still reads on the hot side when I'm driving around town at low to moderate speeds (usually under 35 mph). During these times, the air conditioner doesn't seem to cool very well, either. When I get out on the freeway, the temperature readings drop and the air conditioner works better. What could this problem be and how does it affect both the truck's cooling system and the air conditioner? The secondary problem was going on long before the overheating, but I just lived with it. Now, I might as well fix that, too. In the winter when I'm just using the heater, I often feel cooler air down by my feet. The heater is definitely on and I get heat out of the upper vents and for the defogger, but there's still a cold draft on my feet. Could this problem be related to the air conditioning and overheating situation? If not, can you suggest something else?
Evan McAllisterM
Canton, Ohio

We'll address your second problem first, because it's less involved. Other '97 Ford F-150 owners have reported similar heater problems. In most cases, the source of the unwanted cold air is an improperly sealing door in the ductwork. These inner doors or flaps are supposed to direct hot or cold air to the desired vents. It's hard to inspect interior components of the HVAC system, so take your truck to your local Ford service department. This should be an easy fix for them. Your primary overheating problem sounds like a defective fan clutch. The problem seems to be speed-related, which means that sufficient airflow is being achieved on the highway, but not at slower speeds. This problem isn't unique to Ford trucks; it can happen to any vehicle equipped with a fan clutch. Like any part, these units wear out with age. Your radiator fan is belt-driven. As a means of saving fuel and reducing engine compartment noise, it has a thermostat-operated clutch. The clutch allows the fan to remain idle until heat demands are sufficient for it to engage. It sounds like you're not getting fan engagement at low speeds and normal through-the-grille airflow isn't moving enough air to the radiator and air conditioner condenser. The fan clutch is filled with a silicone fluid that can leak and render the unit defective. There is also a coiled bimetallic spring on the outside of the fan. You should be able to see this spring when facing the fan assembly. When this spring gets heated, it's supposed to operate an internal mechanism that redirects the silicone within the coupling. When the clutch engages, the fan is activated. This mechanism can fail. The fan clutch should disengage, once it senses that there is enough airflow to maintain proper temperature readings without the fan. It sounds like your fan is permanently disengaged, which can cause your low-speed problems. When the engine is cold and not running, you should be able to easily spin the fan. You can check for signs of leaking fluid with a flashlight and an inspection mirror, but this can be difficult to detect. Take the truck for a testdrive and get it up to normal operating temperatures. Then, park the truck and leave the engine running. Observe the fan. If it isn't rotating or doesn't start running after several minutes of idling, the clutch is probably defective. Turn the engine off. Now try to spin the fan as you did when the engine was cold. A working fan clutch should be more difficult to turn, since it should still be all or partially engaged. If it spins as easily as when cold, that's another indicator of a bad clutch.

A Pain In The Gas
I have an '85 Chevy Suburban two-wheel-drive with a 454ci big-block V-8. I use the 'Burban to tow my ski boat in the summer and my snowmobile trailer in the winter. It's a great tow rig, but its biggest shortcoming is its incredible thirst for gas. Getting 10-12 miles per gallon was annoying when gas cost was $1.25-1.50, but now that $3 gas is a reality, that poor mileage is cramping my recreation budget. I have too much time, money, and energy invested in the truck to just bail out, but I was wondering how much trouble it would be to install a Chevy diesel engine until gas prices drop? I know where there's a totally rusted out '84 K-5 Chevy Blazer with a good-running diesel engine. I can get the whole rig for about $200. Since the Blazer and Suburban are virtually the same vehicle, I figured the swap could be pretty easy. Since I'd have to take the entire Blazer, I'd have all the little parts to make the swap. I could just mothball my big-block until the gas situation improves. Does this sound like a good idea? Are there any special things I need to be aware of when making this kind of swap?
Jim Eckhardt
Boise, Idaho

We've received plenty of letters asking about converting a diesel-powered pickup to gasoline, but yours is the first one wanting to go the other direction. Yes, you could make the swap, but why bother? It's an incredible amount of work just unhooking two engines and reinstalling one. Then you want to reverse the process when gas prices moderate. Unless you value your time at less than a dollar an hour, this swap doesn't add up. Where we live, diesel fuel prices are as high as or higher than premium gas, so your savings would be strictly based on the greater number of miles per gallon. The old 379ci GM diesel isn't any all-star in the first place and one out of a thrashed Blazer could be suspect, so why go to all that trouble? You'd be better off conserving fuel by going on fewer outings or picking the lakes and mountains closest to home.

The Late Shift
The automatic transmission on my '92 GMC Sierra shorty has been having shifting trouble. The shifts seem to be getting later and later. That might be fine if I was drag racing, but I'm just trying to get back and forth to work. The truck has the 5.0L V-8 and 700-R4 transmission. The odometer is coming up on 200,000 miles. Nothing has been done to the transmission during the approximately 80,000 miles that I've put on the truck. In addition to late shifts, the transmission sometimes doesn't want to shift at all. It seems like this problem is getting progressively worse. Does this mean I need a new transmission?
Jim Sorenson
via e-mail

You might not need a whole new transmission, but you're definitely overdue for some servicing. Your problem is most likely a sticking or stuck throttle valve. Given your truck's high mileage, things are probably a little gummy inside the transmission. Regular transmission servicing (fluid and filter change) isn't something people think of as they do engine oil changes, but this service still needs to be done. Check the maintenance schedule in your owner's manual. We're sure the recommended service interval is much shorter than every 200,000 miles. This problem with sticky throttle valves has been noted in other '90-'92 Chevy/GMC trucks and related vehicles equipped with the 700-R4 automatic transmission.

Hot Tapes
I've enjoyed the various flame painting how-to stories that you run in Sport Truck. The stories have got me wanting to flame my '02 S-10, but first I'd like to know a little more about the kinds of tape to use. I've noticed that not every painter uses the same materials or techniques. Which tape is best for a beginner? Which width is easiest to use? What about using the big, wide rolls of adhesive masking material and cutting out the flames?
Ron Marks
via e-mail

The number one rule of flame painting is that there are no rules. That's why you see so many different techniques. Most pro painters learned by trial and error. You can avoid obvious problems by reading magazine articles and books on the subject. Motorbooks International (www.motorbooks.com) has an excellent book, How to Paint Flames by Bruce Caldwell (shameless plug) that thoroughly covers all the basic techniques and materials. The best way to determine which tape works best for you is to buy several rolls of different types and sizes. "Fine Line" vinyl tape is the most commonly used product. The 3M Company is the acknowledged leader in the masking tape business, but there are other excellent brands out there. Just be sure to use only automotive tape. Local body shop supply stores can be an expensive place to buy tape. Do an internet search for mail-order body shop supply firms. We've found some excellent tape values that way. The most popular size for initial layout seems to be 1/8-inch tape. It's plenty flexible and it's wide enough for good adhesion of the outer tape layers. Some painters use 1/4-inch tape because they like the thicker lines. You can get extremely thin tape, such as 1/16-inch. We don't care for the wiggle factor in ultra-thin tape, and it's easily broken. The wide rolls of adhesive material that you refer to are known as transfer tapes. They come from the vinyl sign industry. A common use for transfer tape is for quick masking of intricate designs. The transfer tape is placed over the layout tape. Then, the areas to be painted are carefully removed by cutting down the center of the layout tape. This technique takes a precision touch, so the blade doesn't cut through the tape and into the underlying paint. You can draw designs right on transfer tape, which is what many airbrush artists do when creating highly detailed graphics. Again, this isn't something for your first attempt at flame painting. We strongly recommend that you get an inexpensive front fender (body shops often discard barely damaged fenders) to use as a practice surface. You can practice on flat surfaces, but curved items are more like your actual truck.

Steer Crazy
I'm concerned about the front suspension of my '90 Dodge Dakota Club Cab pickup. The truck is a two-wheel-drive model with the 5.2L V-8 engine and automatic transmission. The problem is that the steering doesn't seem as precise as it was when I first got the truck. I haven't lowered the truck or made any suspension modifications. The truck isn't used in any abusive manner, but I do have to travel on about 5 miles of dirt and gravel roads to reach my home. The roads can get quite rutted and full of big potholes during certain times of the year. I never blast through the ruts, but I'm sure they must be hard on the suspension. Is it possible that the rough roads have caused excessive wear in the steering gearbox? I replaced all the shock absorbers less than 5,000 miles ago. Is there an easy way I can pinpoint the source of my problem? Thank you for your help.
Grady Bollinger
Havre, Montana

You should get to your nearest Dodge service department ASAP. Your frame could be cracked where it attaches to the steering box. It's also possible that some or all of the steering gear attachment bolts have fractured. The steering gear can separate from the frame, which is dangerous. There was a NHTSA recall for '90 Dodge Dakota 2WD and Club Cab pickups equipped with the V-8 engine due to this safety problem.


Where's The Beef?
First, I want to apologize if I am e-mailing the wrong person about this-I don't mean to bother you. You recently put out a Sport Truck issue with a small booklet included. This was called Instant Expert: The Audio Edition. It was put out with regard to creating custom consoles/enclosures. I was wondering where I could get this or purchase it? I was very interested in reading it. I appreciate any and all help you can give me. I again apologize for bothering you if I am indeed e-mailing the wrong individual.
Derrick Hawkins
Indianapolis, Indiana

No need to apologize for contacting us; we support our readers and eagerly accept any letters received from them. The issue you are inquiring about was the May '05 poly bag. It included our Instant Expert: The Audio Edition outsert, packed with a variety of good audio tech. Back issues can be found at (866) 601-5199, or go to our website at shop.truckinweb.com.

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