Technical Inquiries: May 2003

Tire Monitors

Q: A flat tire on a motorhome while driving on the highway can be devastating. I have seen reports that tire-temperature and air-pressure monitoring devices can provide advance warning of the impending danger. I plan to replace the tires on my motorhome soon, so this might be the best time to install monitoring devices. However, there’s very little information available about these devices and their reliability. What do you recommend?

Keith Dodge, F103933
Livingston, Texas

A: You’re right; a flat tire on a motorhome or its towed vehicle can be devastating. However, the jury is still out on tire-monitoring devices. Interestingly, there was a discussion about this topic during a seminar at FMCA’s convention in Hutchinson, Kansas. No one could recommend any one product over another, nor would anyone attest to a particular monitor’s reliability.

The best way to keep watch over your tire pressure is to invest in a high-quality air pressure gauge and test your tires on a regular basis, such as before leaving home or the campground. In addition, do a visual inspection to check the tires for bulges, cracking, severe weather checking, and other wear factors.

Some motorhome owners also keep watch as they travel by doing what truck drivers and school bus drivers have done for years: learn the sound that a fully pressurized tire makes when struck with a club. While this isn’t the preferred method, it may serve as an additional check. Get yourself a small wooden bat (such as you’ll find at a toy store) or the thick end of a broken pool cue to test your tire pressures during fuel stops. Give each tire a smart blow with the club and listen to the sound it makes. A deep bass tone indicates low pressure; a fairly high-pitched “thunk” indicates good air pressure. Trust me “” you’ll soon learn the difference between the sounds. Also, slide the bat between the tires on the rear duals to make sure nothing is stuck between them.
“” J.B.

Q: In which issue of FMC magazine can I find an article on auxiliary braking systems for towed vehicles?

Andrew Riess, F286617
Redding, California

A: The most recent article about supplemental brakes appeared in the July 2001 issue of FMC (“Supplemental Braking Systems,” page 60). The article is available online in the “For Members Only” area of www.fmca.com, or we’d be glad to send you a photocopy. Please send a stamped, self-addressed, business-size envelope along with your request to: Editorial Assistant, FMC magazine, 8291 Clough Pike, Cincinnati, OH 45244.

Q: I am writing to you as a last resort, and at the suggestion of my mechanic. I have a 1998 Triple E Embassy on a Ford chassis (460-cid engine), which has slightly more than 26,000 miles on it. This past summer we experienced something akin to vapor lock, which I thought was impossible with electronic fuel injection.

In early July, we were heading home from Wisconsin and were cruising on Interstate 80 through Indiana. It was a very hot day, and we were towing our Mazda Protégé on its Kar Kaddy. Approximately an hour before we planned to stop, we encountered a traffic stoppage. We had been driving at 65 mph and I didn’t think to turn down the dash air conditioning. After idling for a while, I started to move forward, and the engine coughed, sputtered, backfired, and tried to stall. This condition continued as we limped into a campground for the night.

When we departed the next morning, the engine seemed fine “” until we slowed down to pay our toll on the Ohio Turnpike. The sputtering problem happened again. This time we pulled off the road for about 30 minutes, allowed the engine to cool down, and managed to find a restaurant without encountering any further problems. We enjoyed a leisurely meal, and the engine ran fine afterward.

Two local mechanics with excellent reputations said they had never heard of such a thing. Ford Motor Company referred me to a local garage. These technicians also were frustrated, since they were unable to reproduce the conditions that originally caused the problem. A letter to Triple E resulted in the same answer: they’d never heard of such a thing before.

Have any of your experts experienced this kind of problem with a Ford engine? If so, we would really appreciate your help. When we start traveling again this summer, we’ll be nervous every time we slow down if this stalling problem isn’t fixed before then.

Daniel Reid, F262040
North Wales, Pennsylvania

A: Have a Ford technician connect a recorder to your motorhome’s OBD II port to record your engine’s performance. Or, if you’re having difficulty re-creating the problem, another option would be to use a device such as the PDA-Dyno kit from Nology Engineering (760-591-0888) to connect a personal digital assistant (PDA) to the OBD II port, and wait until the stalling occurs again. Turn on the PDA when the problem starts and record the engine’s data. You can save this information and show it to a technician at a later date.

As far as diagnosing the cause of your problem, it could be that the in-tank fuel pump is what’s giving you troubles. But don’t have it replaced until there’s proof that it is the culprit.
“” J.B.

Q: During the past two years I have been experiencing high engine temperatures in my 1991 Itasca Sunflyer, equipped with the Chevy 454 engine. Contacting Winnebago and Chevrolet didn’t resolve the problem, and my local Chevrolet dealer has been unable to duplicate the high temperatures I experience. They usually occur on the hottest days and involve mountain climbs and long interstate runs at highway speeds. Although my engine gauge registers “hot,” I haven’t witnessed any steam or boil-over in the engine compartment. The engine pings when the temperature reads hot, but the temperature always returns to normal on the down grade of each climb.

I performed all of the commonsense changes “” a new thermostat, fresh coolant, flushed the radiator, etc. “” all to no avail. During a recent trip through the Cascade Mountains in Oregon, the engine temperature registered hot through most of the trip. However, Chevy technicians recorded a temperature of only 235 degrees Fahrenheit by reading the ECM output while driving on flat interstate. The engine temperature gauge registered above normal, just below the hot zone, during this road test.

The engine, which has 67,000 miles on it, is equipped with headers and a Gibson high-performance exhaust system. The head gaskets were replaced at 49,000 miles, due to loss of coolant, and the heads were machined. The oil is changed every 3,000 miles. The transmission is equipped with an auxiliary cooler that really works. I had a new water pump installed and fresh coolant added, but no noticeable improvement was seen. I am now convinced that this is a problem that cannot be solved. It appears the engine produces more heat than the cooling system can handle.

Your response to Craig Guest’s technical inquiry, regarding his desire to move up to a diesel pusher (September 2002, page 28), prompts this question: Should I keep driving the Sunflyer until the engine dies, or replace the engine and receive another 50,000 miles of driving covered by warranty? Although I’ve religiously performed all required service on schedule, I am not convinced the current engine will last another five years, given the overheating problem. But replacing the engine and rebuilding the transmission will cost approximately $8,000. Of course, I will likely experience high engine temperatures again down the road. I’ve already spent more than $4,000 on the Sunflyer during the past two years.

The other option is to buy a similarly equipped new motorhome. This is my preferred option, because low interest rates mean I will pay about the same in monthly payments as I am currently paying on the Sunflyer, which I will have paid off in a few months. In addition, this will allow me to benefit from technological improvements now found on new motorhomes.

Col. James Revels, USA Ret., F137049
El Paso, Texas

A: If you don’t mind the extended payment period, buying a new coach might be the way to go. The improvements in type A motorhomes during the past decade are unbelievable. That said, however, I would like to mention a few things that you might try to cool off your Sunflyer’s Chevrolet engine until you trade it in.

While headers do improve the drivability and performance of a motorhome, they also produce more heat for the engine compartment to deal with. If there is room, a good mechanic can install aluminum thermal barriers between the headers and the rest of the engine compartment. This will help deflect the heat away from the engine block.

Next, make sure you have the largest transmission cooler available that will fit in your desired space to achieve as much cooling as possible, and one that is separate from the radiator. These coolers can be routed either in front of the radiator, similar to the air conditioning condenser, which is the easiest, or horizontally below the fan. And make sure that all transmission fluid lines are routed to the cooler and that no fluid goes through the radiator’s reservoir; this will eliminate much of the heat that the radiator is now forced to dissipate. The addition of a larger transmission cooler may take care of your heating problem.

In addition, there are two factors that are commonly overlooked here. The first situation occurs if and when the engine cooling fan’s speed fails to modulate. When the air temperature flowing through the radiator begins to exceed normal, the thermostatic coil on the front of the engine’s cooling fan clutch reacts on a valve within the fan clutch, allowing fan speed to ramp up and really begin moving hot air. (We hear the roar at this time.) When the air temperature is lowered, the fan clutch reverses the procedure, and the fan speed is feathered. Note: The fan clutch for a 454 Chevrolet motorhome engine is a one of a kind and especially engineered and designed to handle this task. To the best of my knowledge, it is produced only by GM and available only through GM dealers and/or an AC Delco parts store. Accessing the correct part number can be challenging, as one must have the stamped number from the original equipment part. If the old clutch is bad, using a substitute may not produce a solution.

Situation number two occurs in part as a result of previous overheating. The electric cooling fan(s) are activated by a sensor in the right cylinder head, which enables the electric cooling fan relay at about 237 degrees Fahrenheit. The electric fan motor(s), being a constant speed type, can only assist in temperature control at best (often too little and too late). I had this situation in the mid-1980s, and I wired an auxiliary switch into the fan relay circuit to turn on the electric fan(s) manually. Now, when a situation likely to create extra load and heat becomes obvious (i.e., a mountain grade), I turn on the electric fans early and it’s not a problem. The two systems mentioned above must function in unison and be in perfect working order to handle the worst-case scenario.

One other thing I might mention: on really hot days, turn off the dash air conditioning and use your roof air by itself. This also will reduce the cooling load on your engine and radiator.
“” J.B. & R.H.