Reaching An Accord
Q: What kind of information do you have on braking systems for towed vehicles? Can you recommend any system? I have a motorhome with hydraulic brakes and I will tow a Honda Accord.
Don Rader, F169185
A: The July 2001 issue of FMC magazine included an article (“Supplemental Braking Systems,” page 60) that provided brief information about more than a dozen different supplemental braking systems for towed vehicles. The systems were not tested. Rather, the intent of the article was to share basic information to assist readers in determining which system best meets their needs. If you no longer have this issue of the magazine, you can gain access to it in the For Members Only area of FMCA’s Web site — www.fmca.com. A login is required. Once you are logged in, click on FMC Magazine Articles and look for the supplemental braking link. If that fails, we would be happy to mail you a copy of the article. Send a self-addressed, stamped, business-size envelope along with your request to the FMCA national office, attention editorial assistant.
Help For The Hungates
Q: We had the same exact problem with the Chevrolet 454 V-8 engine in our 1985 Champion motorhome as Mr. Hungate (“Backfiring In Bossier City,” April 2002, page 24). The backfire would stop the coach in its tracks, and it would quit running while going down the freeway at 65 miles per hour. We had it in the shop on numerous occasions.
We installed new manifolds, new spark plugs and wires, a new ignition module, and new fuel filters (including the little one near the module). I had the old module tested and it was fine, but the problem persisted.
Then, as a last resort, I removed the entire air filter housing. Surrounding the housing is a permanent metal filter, which is filled with a charcoal material. Using a spray can of carburetor cleaner, I washed the charcoal until the fluid ran clear. I also washed the small piece of filter fabric at the small hose intake until it was clean. I let everything dry, put in a new air filter, and buttoned it all back up. It never missed a beat after that and we owned that coach for another eight years.
Jeanne Horner, F286576
A: The permanent metal filter inside the air filter body is known as the flame arrester. Its purpose is to suppress the flame that occurs when the engine backfires through the carburetor. Without the flame arrester, the outer air cleaner element could be ignited by the flame. In your situation, it sounds as though previous backfires belched enough carbon into the flame arrester to clog it, in turn depriving the carburetor of enough air to run under load, thus causing the engine to stall. By cleaning the carbon from the flame arrester, you solved the air intake problem.
A/C, Water Heater Queries
Q: I have a couple of weird questions that I was hoping you could answer. First, our neighbor drives a 1997 29-foot type C motorhome on a Ford E-450 chassis with the V-10 engine. A local RV technician told him that it is more fuel-efficient to use his Onan 4-kilowatt generator to run his overhead air-conditioning unit rather than using the Ford’s dashboard air conditioning while driving down the road (assuming, of course, that the dashboard unit can keep the motorhome comfortable). On a recent trip, he wanted to turn off the dash air conditioning and run the generator and the overhead air conditioning. I think he got some bad advice. What do you think?
Also, I recently had a situation where our Suburban 6-gallon propane water heater’s safety valve opened up and wanted to stay open. This was not the “weeping” that Suburban mentions in the owners manual, as it was a steady stream. Nor was the water anywhere near the 210 degrees Fahrenheit to open the valve. My dealer said I had a weak valve, so I replaced it. Now for the weird question. These valves are supposed to open at 150 pounds per square inch (psi) of pressure. However, we are told that we must use pressure regulators on our city water hookups to keep the water pressure under 50 psi, and we are warned not to exceed that pressure when blowing out the water lines with compressed air. Why don’t the water lines blow out before the safety valve opens at 150 psi? The closed water system is like a hydraulic system where the pressure in one part is the same as in any other part. Are water systems in RVs really built for 150 psi?
Chuck Stewart, F295119
A: Without more specific information, it’s difficult to answer the air conditioner question. However, it’s possible to set up a model so your neighbor can answer the question by substituting numbers into the equation. Suppose that the vehicle is traveling an average of 60 miles per hour, getting 7 miles per gallon without the dash air operating and 6.5 mpg with the dash air operating. By dividing the miles per gallon into the miles per hour, we get 8.57 gallons per hour (gph) fuel consumption without and 9.23 gph with the dash air working. Therefore, in this model, the cost of running the dash air would be the difference between the two (9.23 gph – 8.57 gph = 0.66 gph), which is the fuel consumed by the motorhome due to the added load of the dash air conditioner.
Next, compare the resulting amount (0.66 gph) with the gallons per hour of fuel consumed by the generator. Again, we don’t know what model generator, or the size of the air conditioner, but let’s say that the figure is 0.50 gph. In this model, there may be a slight fuel advantage to running the generator.
However, fuel is not the only cost associated with running the generator. Adding maintenance costs may tilt the advantage to the dash air. There is also the probability that the roof air will not sufficiently circulate cold air to the driver’s compartment, especially in a type C motorhome.
There are a few advantages to using the roof air. First, you will exercise the generator. More people have problems starting and keeping their generators operating because they haven’t been used enough than because the generators are worn out. Also, using the generator will help keep the engine cooler.
I’m sure there are differing opinions on this topic. I would personally use the dash air for convenience, since it is already there, bought, and paid for.
Now for your question regarding the water system. The safety valve on the water heater is a 150-psi valve, and if it opens at a lower water pressure, it is defective. The water system lines are required to be certified for 100 psi. I checked with two manufacturers, and they recommended 50 psi for blowing out the water lines, simply because 50 psi is sufficient and many RVs have a built-in pressure regulator to prevent over-pressure on the system at approximately 50 psi. One manufacturer further stated that it pressure-tests each vehicle during production at 100 psi with water per the code. Hydraulic pressure reaction is not the same as air pressure reaction, simply because the air does compress. The pressures throughout the manifold will be higher nearer the source initially, and would then equalize in a static situation, but not in a dynamic situation.
Q: I have recently found that when the 40-gallon black water tank in our motorhome is full enough for us to see below the floor flange, water drips out under the center of the coach. To me, this indicates that the top of the tank is not sealed or has developed a crack in the seam. Before I begin investigating the cost to have it removed and inspected, do you know whether there is a product that could seal the tank if I mixed it with water and filled the tank to the top? In past years, we used to seal cars with Bards All. Do you have any suggestions?
Richard Moore, F251518
A: First, you need to determine whether the moisture that you find leaking is water or sewage. If it is plain water, then the leak is not in the black water tank. To my knowledge, there is no sealant for holding tanks. Coolant sealers, such as the kind you alluded to, require high water temperatures and metal temperatures to work, so they would not apply in your situation.
Suburban Towed Vehicle
Q: Can we tow a 1994 GMC Suburban 4×4 without hurting the drivetrain? It has a neutral shift on the 4×4 lever.
Mark & Marie Bergeron, F308315
A: Definitely; however, you must consider the Suburban’s weight. Remember, to be completely safe, you must use either an auxiliary braking system in the Suburban, or make sure the total weight of your motorhome and the Suburban does not exceed the gross vehicle weight rating of the motorhome. That’s the gross vehicle weight rating, not the gross combination weight rating.
Conked-Out Cruise Control
Q: I have a 1988 Revcon motorhome with an inoperative cruise control manufactured by A.R.A. This company went out of business several years ago, and my service technician does not know of a source for parts to repair the unit. I am sure that I saw the same problem come up in a “Technical Inquiries” letter a few years ago and, as I remember, there was reference to a company in Kansas that had a large supply of repair parts for these cruise controls. I would appreciate the company’s address and phone number.
William Boutwell, F67586
A: Wow. You have a great memory. We looked in our computer index for a reference to this and found one in November 1991. The company was S.C.S. Frigette. The company’s current address and phone number is 1200 W. Risinger Road, Fort Worth, TX 76134; (800) 433-1740; www.scsfrigette.com.
Q: I have a 1997 Ford Ranger 4×4 with a manual transmission and an electric transfer switch. I want to tow it four wheels down. FMC’s listing states its maximum towing speed is 55 miles per hour. What modifications must be made so the Ranger can be towed at 65 to 70 mph?
Ralph Adair, F263049
Sun City, Arizona
A: When consulting the annual towed vehicle article in FMC magazine (or www.fmca.com), keep in mind that the information included pertains to vehicles of that specific model year and may not apply to previous and future models of a particular vehicle.
To answer your question, there really isn’t any way to modify your Ranger for the higher speeds, short of placing it on a trailer. I did note that although the 2002 Ranger 4×4’s speed is restricted to 55 mph, the listing for the same 2000 model did not mention speed restrictions. What does this mean? Apparently, in recent years Ford has determined that 55 mph is an appropriate maximum speed for towing the Ranger 4×4. There are instances when restrictions such as this are more of a liability issue than a mechanical one, but FMC magazine has no way to determine that. In some cases, the higher speeds do not allow the various moving components, many of which are lubed by gears “slinging” the oil, to be properly lubricated. The best advice is to check the vehicle’s owners manual and follow all recommendations.