I mentioned in an earlier post an engine problem we began to experience in Colorado. We had an intermittent loss of boost pressure causing a reduction of power. When this happened, it set a fault code in the Engine Control Module (ECM) and the engine maintenance light in the instrument panel illuminated. I interrogated the ECM with our ScanGauge D and found a Diagnostic Trouble Code (DTC) telling me that the intake manifold pressure wasn’t at the expected level. Due to the intermittent nature of the issue, I assumed it was a poor electrical connection or a problem with the pressure sensor.
While we were in Abiquiu, New Mexico I investigated the problem and found a crack in the exhaust manifold. This can cause a boost pressure problem. Our Cummins ISL diesel engine is turbocharged. A turbocharger is a device with two chambers in a steel housing – one chamber is fitted to the exhaust system while the other chamber is connected to the engine intake system. Each chamber has a wheel – think of it as a windmill although its shape is more complex than that.
The exhaust side is called the turbine. Hot exhaust is expelled from the combustion chamber and flows through the exhaust manifold and the turbine side of the turbocharger. This spins the turbine wheel. This wheel is mounted to a shaft that passes through the housing and is connected to the wheel on the intake side. This is the compressor wheel. The spinning turbine wheel turns the compressor wheel and the energy transferred compresses the air flowing into the engine through the intake system.
In order to burn fuel in an internal combustion engine, you need fuel and enough oxygen to combine with the fuel. The more oxygen you can pack into the combustion chamber, the more fuel you can efficiently burn and the more power you can extract from the fuel. The compressor side of the turbocharger packs more air into the engine. But there’s a catch. Compressing the air heats it and the turbocharger housing is also very hot. Hotter air is less dense than cooler air, thus negating some of the advantage of pressurizing the intake system. To counter this, most turbochargers use a type of radiator in the intake system – the hot pressurized air is directed through a cooler to reduce the air temperature and increase air density. These coolers are usually an air-to-air radiator called an intercooler or Charge Air Cooler (CAC).
The exhaust leak in our manifold was allowing the hot exhaust gasses to escape before they entered the turbine of the turbocharger. This imparted less energy to the turbine wheel and it couldn’t spin the compressor wheel at the proper speed.
I knew this had to be repaired immediately. In our case, immediately meant when we arrived in Albuquerque. Northern New Mexico is fairly remote and there wasn’t a shop closer than Albuquerque that I trusted. I was still bothered by the intermittent nature of the problem. The exhaust leak was a constant mechanical defect so why was I losing boost intermittently?
We left Los Suenos de Santa Fe RV Park around 11am on Wednesday and stopped for lunch across the street. Then we took US 14 south through the small towns of Madrid, Golden and Antonito avoiding I-25. It was a scenic and leisurely drive – there’s very little traffic and I could cruise without pushing the engine too hard.
We arrived at Rocky Mountain Cummins around 1:30pm and I checked in with their service department. I had an appointment for 7am Thursday morning. We talked about the repair and the time frame. Completing the exhaust manifold replacement in one day was doubtful. They told me I could park the coach and trailer on the street in front and hook up to their 50-amp electrical pedestal.
Donna packed a bag – she would spend the night in a nearby hotel with Ozark the cat. We walked with her suitcase, laptop bag and a couple of plastic bags with cat supplies to the Comfort Inn on 4th Avenue a few blocks away. We walked past a small park with many homeless people sleeping in the shade. We must have looked like upscale vagabonds carrying our stuff past the park. Ozark wasn’t comfortable in the hotel room – she spent most of the time hiding under the bed – she’s so accustomed to her home in the coach.
I stayed overnight in the coach – it wasn’t the best neighborhood and I didn’t want to leave the coach unattended. The Rocky Mountain Cummins shop is fully fenced in with standard chain-link and barbed wire fencing backed up with a 7,000-volt electric fence. On Thursday morning, I dropped the trailer in their fenced lot and checked in for my appointment at 7am – the coach and trailer would be secure in their fenced lot from that point. That’s when things started on a downhill spin.
They weren’t very organized at the service counter. I had talked to the woman there, Barbara, twice in the last week to make sure they had parts and were ready to do the work. She acted like she didn’t know who I was or why I was there. She wrote up the work order and I sat in the waiting area to see how things would progress. At 9am, our coach was still sitting where I parked it.
The service manager, Alvaro, was in a meeting. I asked for him and he left his meeting to talk to me. I explained the situation beginning with the appointment I made a week ago and the estimate they e-mailed me at that time. I also explained the need to get the work done so we weren’t stuck in a hotel. He apologized for the issue and told me the guy that scheduled the work and made the estimate was out of the office. He put someone on the job and work commenced.
I hung around until noon, then went to the hotel to take Donna out to lunch. Wouldn’t you know it, while I was at lunch, Barbara phoned and said Alvaro wanted to show me some issues they found with the engine. I went back to the shop. It was bad news. The charge air cooler had a leak. They pressurized the CAC and showed me where it was leaking. The CAC would have to be removed to see if the leak was repairable. Hopefully a radiator shop can repair it. If it needs to be replaced, it’s not a common part and might be difficult to find. Motorhomes use CACs designed to fit their layout, unlike a heavy duty truck that would use a common part.
The CAC is sandwiched between the coolant radiator and air conditioning condenser. It’s a big job to remove it. They also found oil in the turbocharger and thought it was damaged. I wasn’t convinced it needed replacement. Turbocharger oil seals aren’t like the rubber seals on a crankshaft for example. The shaft is sealed with steel rings, like a piston ring. Seal failure on a turbo is usually the result of a lubrication system problem – I didn’t have an issue there.
Further inspection revealed the source of the oil was the accessory air compressor on the engine. The compressor draws fresh air from the filtered intake air upstream from the turbocharger. The compressor was leaking and some oil was entering the intake system from it. The compressor would have to be replaced.
This was quickly turning into a can of worms. An expensive can of worms. I gathered a few things and spent the night at the hotel with Donna. On Friday, we checked out at noon and moved to the Hotel Elegante on Menaul – a better neighborhood. They had a special rate for Cummins employees and customers. Donna called Uber to transport herself and Ozark while I drove the Spyder. Ozark isn’t sure what to make of our new digs and mode of travel.
After checking in, we went back to the shop to get more clothes and necessities. We will be out of the coach for an undetermined amount of time at this point. While we were at the shop, I looked things over and had another nasty find.
The coolant radiator had corrosion on about a quarter of the fins and the core was about to rust through. It needs to be re-cored. This is the part of the radiator closest to the rear wheels – it can’t be seen without crawling into the engine compartment from underneath and removing the fan shroud. Send more money!
I’m hoping there aren’t any more bad surprises. As my friend and fellow motorhome owner, John Hinton, reminded me – I should be thankful to be getting the repairs made here in Albuquerque rather than being stuck on the side of the highway in some remote area.
Meanwhile, Donna and I are making the best of it, staying at a hotel and taking advantage of the amenities. We’ve also found a few breweries in the area – Rio Bravo, Marble and Tractor. They have great brews that are only found here in New Mexico.
I found a sign on 4th Avenue near downtown – Donna will set me free! I wish she could bail our coach out of the shop.
I’ll update our situation when I know more on Monday.