Friday, 18 July 2014

Grand Mesa National Forest - A Great Place to Fix a Webasto Water Heater

Driving north from Ridgway on Highway 550, the road starts to descend, and soon the mountains are behind you. Past Montrose, the surroundings are flat farmland, and unless you look behind you, there is little evidence of the rugged mountains that you’ve left behind. The descent is gradual, but persistent, and by the time we had reached Cedaredge, we had lost more than a kilometre in altitude.

As with most areas of Colorado west of the Front Range, the flat terrain does not last long, and as we headed north on the 65 we began to climb steeply up to Grand Mesa National Forest. Grand Mesa is a strange site; from below it appears like a giant wall rising out of the valley floor. It is known as the largest flat topped mountain in the world and this is not a misleading description. The climb up to the mesa top is akin to the driving one does on the way up to a ski resort, steep grades and hairpin bends the whole way up, but at 3,000m, instead of finding snowy peaks and roaring mountain streams, you find flat grassy meadows and tranquil lakes. At the top of the mesa, you would have little inclination that you are not at sea level, were it not for the cool temperatures, and the staggering views you get from the edge of the mesa.

One of the many hundreds of lakes on Grand Mesa, Colorado

A view from Grand Mesa, Colorado

Wild flowers in bloom on Grand Mesa

There are hundreds of lakes dotted across the mesa top, and even with the weekend crowds come to fish and drive their ATVs through the forest, it was not difficult to find a quiet spot near some water to camp for the night. We had been warned in advance, and it should come as no surprise given the volume of water in Grand Mesa Nation Forest, but there is a major mosquito problem throughout the forest. After our experience at San Blas, almost any mosquito issue seems fairly tame, but it was still difficult to avoid getting bitten on our forays outside. Thankfully at over 3,000m it is plenty cool enough to leave the doors and windows closed and so we managed to retreat inside when it became too much.

Parked in a quiet spot off the road, I set to work trying to fix our non-functioning water heater. There are a few manufacturers of diesel furnaces for use in boats, trucks and RVs, but the most popular manufacturers for the smaller units seem to be Eberspacher and Webasto. We in fact have units from both manufacturers installed in Jim, an Eberspacher D2 blown air heater which came fitted to the truck when I bought it, and a Webasto Thermotop 50 water heater which we use to heat water and the radiators. The instructions for the Eberspacher units are extremely detailed, and the ones for our air heater, include an in depth description of how to identify the cause of running problems, and how to disassemble and reassemble the unit. For our Webasto unit the same is not true. The water heater came with detailed installation instructions, but the implication beyond, is that if there is a problem with the unit, it should be returned to a Webasto service centre.

A quick search on the internet revealed that there was a licensed service centre in nearby Grand Junction, but not wishing to wait several days, spend lots of money, and buy new parts, I researched how to repair the unit myself. Thankfully, a google search turned up a document written by a chap called Chris Wyles, who has generously taken the time to write a detailed description of how to disassemble and clean the same water heater that we have fitted. Chris’s unit is fitted to a boat, and the description is focussed more on servicing the heater, than repairing it. Nevertheless the instructions are equally valid for our installation and the information was invaluable. Chris recommends servicing the heater every 500 hours, and so I was a little concerned about the failure of our unit after more like 300 hours.

The control of the Webasto heaters is fairly complex, but the way in which they work is reasonably simple. Before diving in and decommissioning the system so that I could remove the heater, I checked the easy things first. I multi-metred the power supply to check that the heater had sufficient voltage to heat the glow pin and operate correctly, and I checked that diesel was being successfully delivered to the heater. With both these checks coming back positive, I set about removing the heater. It is not a difficult procedure, but it is fairly time consuming; thankfully access to the unit is good in the recessed compartment under the entrance matt, in the area that previously housed the weighing equipment under Brinks’s revolving personnel door.

Taking the heater out of its compartment is largely a simple matter if disconnecting all of the wires and hoses, but to avoid the entire contents of the radiators and hoses being dumped into the under floor compartment, I had to first drain down the coolant circuit. I could have avoided this procedure if I’d bought a pair clamps with which I could isolate the hoses to and from the heater, but I had no such clamps in my toolbox. Fortunately, in a rare moment of insight, when I installed the heating system in the truck, I ran a short length of hose for the send and return lines of the coolant loop out of the heater compartment, under the truck, and back in through the floor under the kitchen units. This allowed me to drain the coolant from the radiators and hoses while outside of truck, avoiding getting coolant everywhere, and giving me more space to work. I drained the coolant into a large bucket, and set about disconnecting the power and control cables, the fuel supply pipe, the combustion air intake hose, the exhaust pipe, and the send and return hoses for the coolant.

The space left after removing the Webasto Thermo 50 from Jim the overland motorhome for a service

With the unit isolated, I unbolted it from its compartment and disassembled it on the kitchen worktop. The instructions in Chris’s document are extremely simply to follow, and I soon had the water pump off, the fan and control unit separated from the main body of the heater, and the burner out of the combustion housing, all by undoing the small torx drive screws. The heater was showing symptoms of incomplete combustion and was not making any unusual noises; nevertheless I took the opportunity to inspect the pump and fan unit. Both were clean and operating smoothly, and so I turned my attention to the burner. On inspecting the burner and housing it was clear what the problem was.

Disassembling the Webasto Thermo 50 fitted to Jim the overland motorhome

The coked up burner on a Webasto Thermo C / E fitted to Jim the overland motorhome

The coked up burner housing on a Webasto Thermo 50 fitted to Jim the overland motorhome

The burner housing is a single piece cast metal item, and is comprised of slender ribs and protrusions to increase the surface area and allow for more efficient capture of the heat in the heat exchanging water jacket. The inside of our heater was covered in a thick layer of coke and soot, the result of many hours of poor combustion, and the ribs were barely discernable in places. The story was the same on the inside of the burner itself, and there were thick deposits of hardened carbon all over the combustion surface. I cannot be certain why our heater coked up so dramatically after a reasonably short running time, but I can of course speculate on the causes.

One of the more obvious causes would be contaminated diesel, which could certainly be true in our case. When we left the UK, I tipped about 200 litres of red diesel into the auxiliary fuel tank from which the Webasto unit gets its fuel. Red diesel is nominally just normal diesel that has had red die added to indicate that it has had no road tax paid on it. This is to make it easier for transport cops to spot if a road vehicle is running illegally on off-highway fuel. However, red diesel is not always produced, transported and stored, with the same care as highway fuel, and this is likely to be the case with the fuel that we were using. The fuel had been pumped from the tank on a trailer parked in an industrial estate in East London (normally selling fuel to local construction companies), and had been stored in translucent plastic containers in my garden for nearly two years.  There were plenty of opportunities for contamination, and this may have contributed to the problems with our heater.

Another potential cause, is the duration which we have recently spent at high altitude. These kind of furnaces work by sending small carefully measured pulses of diesel into a heated combustion chamber. The air/fuel mixture is measured to operate correctly at sea level, and with the thinner air at high altitude, the amount of diesel required is lessened. I had heard about people running into problems when they needed heat most at high altitude, and so before we left, I had a high altitude kit fitted to our Eberspacher air heat. The high altitude kit has a pressure sensor in it, which calculates your altitude based on the atmospheric pressure, and compensates by reducing the pulses of diesel. I have come across no such kit for the Webasto heater, and so I left the installation alone. The Webasto heater, had up until recently, worked fine, even at the extreme 4,000m+ altitudes we drove to in Mexico, but I suppose the heater may have been unable to combust the diesel fully, resulting in the carbon deposits that I found.

I cleaned the burner and chamber out as best I could, using a spark plug cleaning brush and a small flat head screwdriver. The chamber was easy to clean to a good standard, but the burner, having an awkward internal shape, made cleaning more difficult. I reassembled the heater as I found it, with the exception of the gasket which seals the burner to the chamber. The gasket must be replaced after disassembly, particularly as the original had cracked on removing the burner. Not having a spare gasket, I used the high temperature gasket goo that I’d bought in Telluride. I reinstalled the heater, refilled the coolant circuit with the coolant that I had collected, and fired the heater up. The exhaust smoked as previously for a few seconds, before the smoke cleared and the unit heated up and ran perfectly. I left the heater running for three hours and it operated with no problems. I bled the circuit fully, refitted the floor hatch and expansion tank cover, and retired from a successful repair.

In the morning, after a long hot shower, we left our campsite, and set about exploring the forest. We hiked along the rim of the mesa, before driving out to the Land’s End viewpoint to admire the sweeping views over Colorado and Utah. From Land’s End, it is possible to see more than 60 miles, taking in the canyons of eastern Utah, and the 14,000 foot peaks in the San Juan Mountains. The view is awe inspiring, and thankfully, after a short search, we found a place to camp nearby with an equally impressive view. After a brief but impressive thunderstorm, we enjoyed watching the sun setting over the plain, 1,500m below the mesa.

Looking towards the San Juan Mountains from Grand Mesa, Colorado

Jim the overland motorhome parked off Lands End Road on Grand Mesa

Sunset looking towards Utah from Grand Mesa, Colorado

Sunset viewed from Grand Mesa, Colorado

The next day we left our campsite via the short but rocky road that led down from the highway. The video of our exit shows the sometimes alarming way which Jim pitches as he crawls over the uneven surface. The black smoke is a consequence of me nearly stalling the engine. As the gearing in first gear is not high enough, I have to keep the engine revs lower than would be ideal to keep the speed low. This sometimes means that I get close to stalling the engine on steep sections or larger obstructions.

315/80R22.5 Michelin XZY3 tire deforms over a small rock on Jim the overland expedition motorhome

To avoid having to drive a stretch of interstate to get to our next stop of Glenwood Springs, we would have had to drive back the way we had come on Highway 65, and thread a winding route through the mountainous wildernesses of central Colorado. This would have added 40 miles to our journey, and taken us high over the McClure Pass. Instead we took the easy option; we drove back to the tarmac, and continued north and west along Highway 65, headed for the I70. The road descends from the mesa in a similar way to the ascent on the other side, but once past the small town of Mesa, the scenery changed dramatically. For a small while it felt like we’d left Colorado and were back into Utah again, as the road wound through a deep canyon cut through the red rock. The canyon petered out as we approached the I70, and for the first time since leaving Cedar City on the west side of Utah, we drove a stretch of interstate.

The interstate roads in America are certainly a fast and efficient way to move around, but they can be incredibly dull, and are generally an excellent way of missing everything worth seeing as you drive through a region. On the whole, I intentionally plan our routes to avoid using the interstates, but on the odd occasion that we do use them, I appreciate the break from constant gear changes and hard concentration. Travelling at Jim’s top speed of 55mph, we were soon in Glenwood Springs, and it didn’t take long for us to find places to restock our food and diesel supplies, and find a place to park for the night.


  1. Did you install marine suspension on Jim as he rolls like a boat!?

    Hope you guys are good.

    P.S. you may be able to adjust the air vanes to increase airflow around the heater jet nozzle, or get a nozzle with smaller diameter to cope with altitude better.

    Keep up the adventures


  2. Hi Al,

    Good to hear from you! I hope all's well with Ruth, Meta and the dock?

    If by marine suspension, you mean ballast, then yes, lots of it. The rocking does make me nervous, but we've been at much worse angles than the video.

    The standard way of modifying the webasto for high altitude is reducing fuel, either by modifying the controller, or more simply by adding an adjustable bypass valve to the fuel pump. Changing the nozzle would be a ball ache for a day or two at altitude.

    We got our first taste of proper bass since leaving London a few days ago. We saw Nine inch nails with a huge d&b system. Lots of Jinfra.


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