Hapy Heat Repeat (Part 2)

Continuing the efforts on creating some cabin heat in the old microbus, today's post covers sourcing the air for the heater from inside the bus.

Grounding

air sourcing from inside

In the last post on this topic, I mentioned that the prior attempts, and the original heat, for that matter, all pulled in air from the outside. The original heat pulled from the engine bay, sent it through heater-boxes (insulated boxes around the exhaust manifolds) and then up to the front of the bus. There was even a booster fan to push air when the engine speed was too low to push air. Years ago, I added a bilge-blower fan mid-stream to help get the air forward, and replaced large sections of pipe with insulated hose. In the end, the original system at-best, delivered warm moist air when it was raining (again, it's Oregon so that's 8 months of the year). When not-best, we got cold moist air that smelled like oil or exhaust.

When I did the ALH-TDI engine swap, I removed the original system rear of the front frame, setting a Vanagon rear-seat heater against that frame crossmember. While it didn't leak for a while, it started leaking again this past year. The unit was really never up to the task, and since it was only designed to heat the rear of a Vanagon cabin, I was probably asking too much of it. Still, it was a significant improvement over the original and bilge-blower-enhanced systems. The air was warmer more often, and exhaust-smelled less often. Overall, though, it was not "warm" in Hapy from the use of the heater, and the issue with moist air remained.

Fast forward to the Maradyne heater I just installed. Unlike the Vanagon rear-seat heater, the Maradyne is a 3-row heater core and it is almost twice the width. The core alone could provide considerably more heat. The fan is way more powerful too, so moving that heat into the cabin will be that much more  effective. What remained, however, is the air is still sourced from below the bus, so the wet roads will provide an endless supply of moist air to fling onto the inside of the windscreen. I hope I resolved that with the changes below.

Maradyne Heater Prep

purists love this

In the last post on this topic, I described how the heater was installed on an angle to minimize the ground clearance impact and so the outlets point more directly at the original air pipe. This orientation, however, meant that the brackets were hanging into the space where air intake hoses would go. So, first order of business was cutting those brackets down with the death-wheel (angle grinder). Once cleared, I could easily see that the coolant outlet jutted too far into the same air-hose space so I cut it down as well. Last, I changed the hose from the outlet from a straight hose to a 45* angled hose, routing the coolant above and away from the air inlet. While the inlet is not completely exposed now, it is considerably better. The inlets are 3" diameter and have a lip that's maybe 3/8" for a hose to fit onto. I had intended to add something more substantial for the hose to attach to, but once I got into it, I concluded that the original fan housing could hold a hose and clamp. Time will tell, and I am retaining the extensions I bought for this purpose in case I need to add them in later.

Holy Bus

Well, more like holey bus. In order to send air from inside the bus to the air intake on a fan system that is outside the bus, I need to add a hole or 2 for the air to pass through. I did not want to put air intakes in places where I would accidentally spill water (or other beverages), or get dirt and the like into it. I also did not want the air intakes to be so close to the front that the fan was effectively pulling the warm air right out of the outlet vents. I applied some cold-air-return thinking and chose to put one intake inside the rock-n-roll bed base cabinet. This cabinet is probably the coldest space in the bus (second only to my feet) and the vacuum created by the fan will draw air from the front to the back, creating room for the warmer air to enter the bus more freely. Of course, it's not like a 50+ year old microbus is sealed, but my 70+ year old house isn't either and once I tied the cold air intake into the house system, the house grew measurably warmer.

From underneath, I considered where there was a space without structure nor pipes to interfere with the air intake plumbing. With the radiator, wiring, original stuff and everything else, it is quite busy under there, but there is a space just behind the rear cross-frame (think: rear jack-point) but in front of the rear wheel well that is inside the cabinet, nearest the front outer edge. I tested a few spots with a drill to make sure that I could fit a 3-1/2" circle without hitting something neither underneath nor inside the cabinet and found a good spot. I cored a 3-1/2" hole with a hole saw. Why 3-1/2"? The inner diameter of these hoses is 3", and I felt that leaving a little extra room for wiggling was better than having it tight as would have been with a 3-1/4" hole. This turned out to be a wise decision. Once the hole was cut, I shot it and the support brackets with paint to delay (can it really be stopped when it rains 9 months of the year?) rust.

Fitting

cabin air intake

Once the hole was cut, I was on the home stretch. I found what look like air outlets with metal grills that fit a 3" hose to act as an air intake screen. I a-fixed one end of the hose to the grill, cable-tied it to be double-sure and passed the hose through the hole from above. The hose barely fit. It was so tight, I had to cut off the cable-tie because the cable tie end prevented the grill from sitting flat on the floor. Anyway, I chose an orientation that pointed the grill away from the center of the cabinet so things don't accidentally fall in or over it and then screwed it down to the wood floor of the cabinet. From underneath, I stretched out the compressed hose, stretching it along the side of the radiator, and turning it towards the fan.

I had initially planned to have 2 air intakes, one per fan intake, but after cutting the passenger-side hole, decided that I had 3" of outlet, so having only 3" of inlet was actually a fair balance. So, rather than run 2, I added a 3" wye along the passenger-side frame rail. I sent the stretched and then cut hose into the base of the wye and shifted to the fan inlet on the driver side, knowing it would be the harder of the two. I can always choose to add a driver-side inlet, but with the furnace on that side, there will be additional complexities.

The driver-side was definitely harder, but simply because the coolant outlet hose still ran across the air flow path. I twisted and bent the air hose and jammed it onto the inlet lip. I added a hose clamp while pressing the hose onto the lip, threading the clamp until it was quite secure. Content, I stretched out the hose, threading it behind the fan housing, but in front of the radiator intake to the passenger side. I added a cable-tie on the driver-side to hold the air hose in place. I cut and then sent the other end of the hose into the wye. It got another cable-tie up to the underside of the bus before it entered the wye.

The section from the passenger side air intake to the wye was a little over a foot, and was the easiest part of the install. I attached to the fan intake first, adding a hose clamp, of course. Once stretched and cut into the wye, I cable-tied the wye up near the floor of the bus, mostly out of sight. I cable-tied the passenger-side hose as well so there would be minimal pressure on the hose clamp. At this point, the air intake for the cabin "climate control" sourced from the inside of the bus.

Testing

ground clearance mostly unchanged

All that remained was testing the system, both for air flow as well as coolant. I started with the air flow, accepting that I could confirm that without running the engine. As expected, the fan blows hard, and draws through the inlet. Because the inlet is inside cabinet, it make less noise than it might have had it been placed elsewhere. Still, I will need to be aware of it when we pack things so it is not even remotely blocked.

Satisfied, I exposed the top of the engine and started it up. I had expected to simply add coolant/water while air bubbles appeared but 2 things interrupted that plan. First and worst, the injector pump started leaking all over the place. Now, to be fair, I had smelled diesel on my last couple of drives, so this was not 100% a surprise, but it still was a little bit. Second, air bubbles did not really appear. I will need to bleed the heater core segment, once I replace a seal or two in the injector pump. A seal set has been ordered, so until the kit arrives and is installed, Hapy will sit.

That's where we are at this point. I may try to bleed the heater while I wait for the seal kit, but it will depend on the weather and my workweek. Thanks, as always, for following along. More next time-