It’s 7am Tuesday morning as I write this. We’re at the KOA campground near St. Mary, Montana. It’s at the east entrance to Glacier National Park. It’s a bit chilly this morning, 47 degrees. The elevation here is 4,500 feet above sea level. The sun just rose over the eastern ridgeline across the St. Mary River. I expect the day to warm up quickly.

The past few days we covered a lot of ground. I’ll have to break this up into two posts as the tale will get too long.

Sunday morning we left the Walmart in Sheridan, Wyoming. I topped up the fuel tank with 44 gallons of gas. We left I-90 and headed west on WY14. This route took us over the Big Horn Mountains. It has several long, steep grades and finally tops out over 9,000 feet above sea level at Granite Pass. It was slow going. Compounding the effort of the steep grade was a stiff head wind from the west.

In a situation like this, it’s tempting to just mash down on the pedal and give her all she’s got. I’m more sympathetic to machinery than that. In my opinion, running at wide open throttle for extended periods of time is not conducive to long-term durability. So, on long, steep climbs I gear down, allow the vehicle speed to drop and maintain a reasonable load on the powertrain.

In the Big Horn Mountains and later in the Absoroka Range, it meant dropping to second gear and slowing to 35-40 mph or less at times. Our rig is powered by an 8.1 liter (496 cubic inch) GM Vortec gasoline engine. Normally aspirated gasoline engines suffer from a double whammy when traveling through high mountains.

Climbing up in the atmosphere, I’m requesting enough torque to propel a rig weighing over 25,000 lbs upward against gravity. We also have the drag coefficient of a barn door to overcome against a headwind in this case. The real issue that becomes a factor though is called density altitude . As we climb higher, the air becomes thinner.

Internal combustion engines work by combining fuel with oxygen in the air and burning it. As the atmosphere becomes thinner, there are fewer oxygen molecules to combine with the fuel. The fuel injection system senses this though the exhaust content and regulates the amount of fuel injected to maintain the proper air/fuel ratio. The ambient temperature rose into the 90s, further thinning the air. Bottom line is less fuel equals less power.

So here we are, climbing over a 9,000-foot pass with a heavily loaded RV and our engine isn’t capable of producing maximum power. That’s why I’m in second gear and plodding along. I was wishing for a turbo diesel engine at that point. Turbo chargers were originally developed for aircraft. Turbochargers negate the effect of altitude as they force air into the engine.

Alright, back to our story. Once we crested the summit, we had to contend with steep downhill grades. When I say steep grades, WY14 has grades as steep as 9%! I used second or third gear on the down grades to utilize engine compression to retard the pull of gravity. Engine compression alone isn’t enough to stop us from speeding down the mountain. I would stab the brake pedal hard enough to quickly reduce our speed by 5 mph, then release the brakes and allow them to cool.

I repeated this procedure as necessary to maintain my desired speed. Riding the brake to keep a steady downhill speed results in over-heated brakes which become ineffective. Scary thought.

We stopped in a little town called Graybull. I parked on the street and took a stroll while Donna made our lunch. The town was quiet; all of the shops were closed on Sunday. After lunch we continued west. The terrain was mostly flat. It had the appearance of badlands at times. Other parts were agricultural. The headwind became even stronger as the day wore on.

Bicyclists know headwinds can be demoralizing. This is also the case in a big vehicle with poor aerodynamic qualities. The slightest uphill grade required me to de-activate the overdrive and run higher rpms for power.

Eventually we began the climb up the Absorokas into Yellowstone. This climb is every bit as hard as the climb through the Big Horns. We were in second gear through much of the ascent. The viscous coupling on the radiator fan was fully engaged most of the time, drawing air through the engine coolant radiator and transmission cooler. When it’s fully engaged, the fan makes a roaring sound. Normally the speed of the vehicle passes enough air through the radiator and the fan is not engaged.

While climbing in second gear at 30-35 mph, the engine and transmission are heating up and the normal airflow through the radiator isn’t able to keep the temperature under control. The fan does a good job though. Our coolant temperature would quickly drop to 195 degrees with the fan engaged.

At the entrance to Yellowstone National Park, we pulled in behind a car at the toll gate.  As we sat there idling with A/C keeping us cool, I was mindful of how narrow the gate was. I was concerned about catching a side view mirror as we passed though. The car in front of us must have been playing 20 questions with the park ranger.

We sat for several minutes before they pulled away and we could enter. I showed the ranger our National Parks annual pass and was given some literature and waved through. I pressed the accelerator and felt the engine start to pull, then I felt a loss of power. The engine rpms went down to 300, fluttered a bit and then the engine died.

This never happened before. I restarted the engine. When I put it in gear, the rpms went down again and it stalled. Uh oh. I cranked it over again and it started. I revved the engine once it started and it seemed okay. I put it in gear and it was fine as we pulled away.

The east entrance to Yellowstone is a steep uphill grind. Here we go again in second gear with the radiator fan roaring. The speed limit was 45 mph but at times, I couldn’t maintain that without running pedal to the metal. At one point I pulled into a turn out to let a few cars following me go past.

I sat there idling for couple of minutes as more cars appeared from below. Finally there was a break in the traffic and I started to accelerate out of the turn out. I felt the engine lose power, the rpms dropped to 300 and then it stalled. This time it wouldn’t start when I cranked it over.

I got out and looked in the engine compartment. The under hood temperature was quite high. I thought about the series of events. It wasn’t a misfire that would suggest an ignition problem. It felt like a fuel delivery problem. Donna asked me what I was going to do. I said we do nothing. We wait a bit and the let wind cool the engine compartment.

My theory was that we had fuel boiling in the fuel rail. The fan was pulling hot air through the A/C condenser, the transmission cooler and the engine radiator. This was creating high under hood temperature when we were stationary or moving slowly. Boiling fuel in the line is known as vapor lock.

After ten minutes or so, the engine fired up and we were on our way. I was pretty confident in my diagnosis. We climbed to the summit in second gear. As we crested the summit, I put the transmission selector into drive and released the pressure on the accelerator pedal so it would upshift. When I did that, something didn’t feel right. I watched the tachometer drop to 300 rpms, flutter, then fall to zero as we coasted down the other side of the summit.

I told Donna the engine quit. I said we can coast down hill and it will quickly cool. I also told her I no longer had power steering without the engine running. She wasn’t thrilled about coasting down a steep grade without power steering. She asked if we had brakes. The ABS brake system on our chassis has a back-up electric motor on the ABS pump. I told her brakes were not a problem and concentrated on steering.

We picked up speed and were coasting down the hill at about 40 mph. At that speed, the steering effort wasn’t too high. There was an incline ahead. The incline would slow us down, possibly even to a stop in the middle of the road. There wasn’t a shoulder to pull off of the narrow roadway. At the bottom of the grade I spotted a turn out on the left side of the road that looked just big enough for us to fit. I muscled our rig into it as I braked to a stop. If my vapor lock theory was correct, coasting down the hill should have cooled the engine compartment. I started the engine. It fired up and we drove away.

At this point, I smartened up and turned off the dash A/C. Air conditioners convert refrigerant from liquid to gas (thus cooling) and back to liquid in the condenser. To convert back to liquid the condenser must remove heat from the refrigerant into the air. How stupid could I be? Running the dash A/C in these conditions was adding heat to air pulled by the fan into the engine compartment. We quit using the dash A/C and had no further stalling episodes.

We found suitable parking at Lake Junction and walked to the information center. The information center had taxidermy displays of a variety of birds found in the park. I like to identify birds and enjoyed the displays.

Behind the center is Yellowstone Lake. The lake is large and we found sandy beaches here. A couple asked if I would take their picture with their camera. I did, then I realized I didn’t have a camera with me. I left everything back in the motorhome. Doh!

We dove through the park to Mammoth Junction. Driving through Yellowstone National Park in a large RV is not ideal. With our cargo trailer,our overall length is about 50 feet. We couldn’t stop in most of the pull outs. There were cars in them and not enough room for us to stop without having the trailer in the road. We cruised along and took in the scenery. There was a six-mile stretch where stopping was prohibited. There were fire crews working. We didn’t see the fire though.

The roads were narrow with no shoulder. If you’re planning to visit Yellowstone in a class A motorhome,I recommend staying in a RV park nearby and entering the park in a smaller vehicle.

We saw several bison. It was a novelty at first, but it became a nuisance. Anytime buffalo were near the road, cars would stop. People would hang out the window to take a picture or shoot video. Traffic jams formed as the scene was repeated. I can understand stopping your car when buffalo are in the road, but to come to a stop in the roadway because you want to take a picture of a buffalo nearby makes no sense to me. . Maybe I was just getting tired and cranky.

While we were stopped in traffic Donna snapped a couple of pictures through the windshield

We exited the park and entered Montana at Gardiner. Outside Gardiner, we stopped and had a snack while we stretched our legs. From there highway 89 follows the Yellowstone River north to I-90. We drove to Bozeman and stopped at Walmart there.

I’d read tales of Walmart RV parking in parts of Montana. So many RVers pass through the area during vacation season, the Walmart parking lots fill with RVs. We found quite the assortment in Bozeman. To be continued…

(Click on photos to enlarge)