Subscribe to the Free
  • |
  • |
  • TDC - Technical Questions & Answers - May 2005

TDC - Technical Questions & Answers - May 2005

Bruce Caldwell
May 1, 2005
Cool School
Q: I bought an '86 GMC shortbed pickup with marginal air conditioning. It does blow air, but it isn't very cold, so I'm pretty sure the refrigerant is either gone or else very low. Right now I'm more concerned about heat than cooling, but summer will be here soon and I would like the A/C to work well. It gets pretty warm in Missouri during the summer.
My questions concern what is the best way to refurbish or repair the air conditioning. Can I still use the old R-12 refrigerant, or must I use the new R-134a? Can I do some or all of the work myself? Does the new refrigerant work as well as the old stuff? When I'm recharging the system, is there anything else I can do to optimize the air conditioning. I hope you can give me some cool advice.
Jeremy Jonstadt, Springfield, MO
A: "It depends" is the best way to summarize your questions. The answers depend on many things, including local regulations, supplies of R-12 refrigerant, and how good or bad your definition of marginal is.

You need a baseline analysis of your current system. A repair shop that is certified to do air conditioning work should be your first stop. The shop can evaluate your truck and explain your options.

If your current system is simply low on refrigerant, but otherwise in good working order, you're probably fine sticking with R-12. Air conditioning systems that were designed to work with R-12 obviously work best with R-12.

R-12 was replaced with the more environmentally friendly R-134a in 1996, but R-12 systems were allowed to be recharged with new R-12 as long as supplies lasted. Prices shot up and there was some hoarding, but as prices increased, more R-12 seemed to find its way out of the woodwork. Your local air-conditioning expert can tell you about current prices and supplies.

Converting an R-12 system to R-134a typically reduces performance by approximately 5 to 15 percent. The percentage depends on the efficiency of your condenser. This performance drop will still seem like an improvement compared with a truly marginal R-12 system.

If your current air-conditioning system needs any of the major components replaced, such as the compressor, condenser, or evaporator, it makes much more sense to update the system to R-134a. The ease and cost of the conversion is related to the age of the vehicle and the current components it has. Systems that already have barrier-style hoses and R-134a-compatible seals are much easier to convert.

Federal laws state that new R-134a fittings must be used on the high and low service ports. That's to prevent anyone from trying to recharge an R-134a system with the old R-12 refrigerant. To help avoid this problem, warning labels are supposed to be installed on retrofitted A/C systems.

It's not a good idea to mix types of refrigerants. Doing so will seriously affect the performance of the system by increasing operating pressures. Excessive pressures can overstress the compressor to a point of failure. R-134a compressors can also fail from the use of incompatible lubricants.

You should have air-conditioning servicing done by a professional shop. A prime reason for letting the pros do the work is that they have the specialized equipment necessary to safely evacuate the old refrigerant. People who just let the old refrigerant escape into the atmosphere are harming the environment.

A typical retrofit conversion includes evacuating the old refrigerant, replacing the accumulator with an X-7 desiccant unit, installing new O-rings, installing a new high-pressure cutout switch, changing the orifice tube, adding PAG oil, and recharging the system with new R-134a refrigerant. Once your truck has been converted, it will be easy to have it recharged if necessary.

There is some capacity loss when an old system is retrofitted to R-134a, but there are ways to regain some of that loss. There are aftermarket orifice tubes with a variable valve (instead of the old fixed tubes). Variable tubes change the flow rate for improved low speed and idling A/C performance. Lowering the outlet air temperature with a variable valve can reduce temperatures by 5 or 6 degrees.

A larger, more efficient condenser is a good idea when going to an R-134a system. Whenever an old condenser or evaporator needs replacing, be sure the new unit has a BTU rating as high or preferably higher than the original unit.

If you decide to stick with your current R-12 system, consider adding an auxiliary cooling fan. A separate electric fan for the air-conditioning condenser will improve A/C performance at idle and when crawling along in traffic. By dissipating excess heat, the air-conditioning system doesn't have to work as hard.
Shaft City
Q: There's a ringing noise that won't go away in my '94 Dodge Ram pickup. I don't abuse the truck, but I don't baby it, either. The noise is loud enough that several friends have commented on it. It sounds like the noise is more underneath the truck and toward the back rather than coming from the front of the truck or the engine compartment.
The sound is definitely a ringing, metallic sound as opposed to a grinding or thumping sound. I've crawled around underneath the truck several times looking for loose parts. I've tightened all the fasteners I could see and didn't find anything overly loose. Do you know of any ringing noise problems specific to my truck, or can you suggest any areas to check out? Thanks for your help
Ben Lewis, Pocatello, ID
A: Troubleshooting noises are difficult in person, much less by letter. Driveshaft problems can produce ringing noises. Similar ringing noises have been encountered on a number of '94 and '95 Dodge Ram pickups, so Dodge released an improved driveshaft. The new unit is insulated. It's listed under part number 52105260.

Another noise problem related to '94 and '95 Ram trucks is a frontend rattle or clunking sound. If you encounter that noise, check out the antisway bar links where they attach to the antisway bar.
Photo 2/3   |   tdc Technical Questions Answers gmc Truck Cartoon
Four Power
Q: Are there any relatively inexpensive things I can do to improve the performance of the 2.2L four-cylinder engine in my '98 Chevy S-10 pickup? I'd prefer bolt-on modifications. I don't expect V-8 power, but I'd like to not be the slowest truck on the block. Is there anything I can do to improve the shifting quality of the five-speed manual transmission in my truck? Any suggestions would be appreciated.
Nelson Bradford Jr., via e-mail
A: Most buyers choose the 2.2L four-cylinder for economical reasons, both in terms of initial cost and fuel economy. Depending on the condition and how attached you are, you might consider selling the truck and finding an S-10 with the 4.3L V-6 engine. Besides its extra 35 to 75 horses in stock form, the V-6 is much easier to hop up.

There are some basic changes that will provide extra power for your present engine. One of the simplest changes is to replace the stock air filter with a K&N Filtercharger or similar hi-po filter. Remove any of the little restrictors between the air inlet and the throttle body. These restrictors are designed to reduce air intake noise. Removing them gives incoming air a straighter route to the throttle body.

Another simple change is with the thermostat. Install a 160-to-180-degree unit to lower engine temperatures. Lower air inlet temps help reduce the possibility of detonation.

A custom programmed computer chip will help get the most power your engine has to offer. Companies such as Hypertech [(901) 481-8800,]can set you up with a customized computer chip.

A local muffler shop that has experience with high-performance exhaust systems may be able to make some modest improvements to your exhaust system. We don't know of any company that makes exhaust headers for your application, but a performance muffler and catalytic converter should provide a little extra boost.

There is a Hurst Competition/Plus shifter available for S-10 pickups with the New Venture five-speed transmission. It will give you shorter throws and smoother shifts.
Rough Stuff
Q:The idle on my '86 Ford F-150 pickup is pretty rough and very annoying. The truck is a shortbed regular cab with the 300ci straight six-cylinder engine and the five-speed manual transmission. I've always liked this combo in a relatively small truck like mine, because it has good torque and gets reasonable fuel economy. I use the truck for daily commuting.
I took the truck to two local independent repair shops and they wanted to sell me everything but the kitchen sink. Their estimates were both well over $1,000, because they wanted to do things such as a valve job and replace a bunch of sensors.
Before I dump that kind of money into an almost 20-year-old truck (with more than 200,000 miles on it), I thought I would seek your opinion. Are there any simple things that I could check out myself to save some money?
Kevin Jakowski, Stockton, CA
A: Rough idle problems are common for all makes and models of cars and trucks. We get lots of letters on the subject. Rough idle problems were common back in the days of simple carburetors and no smog equipment. The engines were less complex and solving rough idle problems was relatively simple.

Today's sophisticated engine management systems mean there are more things that can affect idle quality. That means it's harder to diagnose. Ford has issued some Technical Service Bulletins that could apply to your truck.

TSB 87-3-20 suggests a number of checks involving variations within vehicle calibration limits. One of the checks is inspecting the condition of the engine mounts. This is something you could do yourself. Ford has a redesigned fuel inlet needle and seat assembly that's detailed in TSB 85-16-22.

Vacuum leaks are a common source of rough idle problems. TSB 86-9-11 deals with vacuum leaks and problems involving the electronic engine control system.

An improperly fastened exhaust or intake manifold can cause rough idle problems. TSB 86-9-18 covers checking for properly torqued bolts. This is something you can do if you have a torque wrench.

A couple other possible problems could be a defective MAP sensor, a bad idle solenoid (a strong possibility), or a defective coolant temperature sensor. You could just replace these parts hoping to stumble onto the cure, but you'd be better off taking the truck to a Ford dealership.

As to the pros and cons of spending a grand or more on an older truck, that's a decision only you can make. It's very easy to run up a thousand-dollar bill at a repair shop given the high cost of labor and parts. If the rest of the truck is in good shape and you still enjoy driving it, we'd get it repaired.
Elevation Escape
Q:I bought my wife an '04 Ford Escape. She loves it and doesn't want me to start modifying it like I've done to my Ford Lightning. She did agree to let me lower the Escape a little as long as it doesn't screw up the ride. Do you know of anyone that makes a lowering kit for Escapes? Is this something I could install myself?
Xavier Montoya, via e-mail
A: Ground Force [(724) 430-2068,] has a new 2-inch lowering kit (#9973) for '04-'05 Ford Escapes. The kit consists of four lowered coil springs.

Swapping coil springs is something someone with a reasonable amount of mechanical ability should be able to do. The important thing to remember when working with springs is that they can be very dangerous due to their stored energy. You should have the suspension alignment checked after installing the new springs.
Photo 3/3   |   tdc Technical Questions Answers cartoon
- OF


Subscribe Today and Save up to 83%!

Subscribe Truck Trend Magazine

Subscribe to:

Truck Trend

Subscribe Diesel Power Magazine

Subscribe to:

Diesel Power

Subscribe Truckin Magazine

Subscribe to: