Defrosting - Part 2

First, happy belated Summer Solstice. Our annual pilgrimage to Bend for 4Peaks which usually coincides with Summer Solstice and Father's Day was thwarted by CoViD this year. So, we are taking the side-lining as an opportunity to fix or upgrade things on the bus that are just too hard to do in the cold and rain. It seems with every improvement, I discover 2 more opportunities. Today (hopefully) begins the end of the defrost epic. In my last post about the defroster, I provided background. Today, I get started on the plan I described.

Tear Down
While I had disconnected the electrical from the Vanagon rear heater a while back, the coolant lines were still hooked up. So, my first step to removing it was unhooking those hoses. The clamps are easy enough to loosen with a Phillips screwdriver, and I was able to back the hoses off the barbs with a slotted screwdriver. With each one, I quickly moved the hose end into a clean bucket to catch the coolant. Once the lines and the heater were drained, I could extricate the heater unit from the shelf. With all of the wires and cables, this took a few minutes, and the resulting empty shelf doesn't look much better. Quite the contrary, actually, but, it does create a much better space for me to re-arrange the wiring one day. Yeay, more work.

Defroster Placement

valve shown closed

With the Vanagon rear heater in-hand, I could try out some ideas for how to fit it under the bus. The radiator sits just in front of the rear cross-beam, leaving a little over a foot between the front edge and the front cross beam. It is into this small window that the heater will fit. I held it up and thought about my options. If held right-side up with the front edge of the heater parallel to the cross beams, the coolant barbs would be facing rearward on the passenger side and the mounting tabs would be on the bottom. There looked to be enough space in front for a cowling or register to be put so the approximately 9" by 6" rectangular box could winnow down to the 3" diameter circle of the old air channel. The angles would be kind of sharp, but the air flow would be direct.

If the heater unit was turned sideways, the barbs would face the driver side. The air would need to make a hard left and it didn't look like there would be much space. So, I rejected that orientation.

I tried flipping the heater upside down, back in the parallel-to-the-front-beam position. Like this, the barbs were still on the driver side, but facing rearward. Since the coolant lines leaving the engine were also on the driver side, this was preferable. The drawback to this set up is that the bleeder screw is on the bottom, not the top. So, getting the air out of the system could be more difficult. In contrast, though, the mounting tabs were now on the top, so any attachment would be greatly simplified. The simple attachment won the decision. In this orientation, the valve for allowing / preventing coolant into the heater core was also on the driver side, sliding forward and aft for open and closed (respectively).

Defroster Mounting

safety hole drilled

Before I could consider routing coolant and air, the rear heater needed to be attached. The mount holes are exactly 7" apart. So, I found the centerpoint in the air pipe and measured 3-1/2" out from each. I aligned the heater on those lines and pushed it as far rearward as I could before it touched the debris-grill on the radiator. My thought was that the more gentle the angles in the air register, the more easily air would flow into the old pipe. As is, the front of the heater is about 4" back from the front cross-beam. Once the spots were marked, I drilled 2 holes through the floor. Through these holes, I sent a pair of 2" long bolts. From below, I nutted down against the floor with a pair of nuts, then added another pair less than 1/2" from the ends. I slid the heater unit onto the bolts and then nutted it down with another pair of nuts. So, that's bolt head | floor | nut - some space - nut | heater | nut. I put some threadlock on the bolts. Before I added the heater, I set an extra (safety) hole through the mounting tabs. Through this hole I sent a cable-tie, and then looped each side up to the pipe that the transmission shifter runs through. I figured that if the nuts found some way to work themselves free, the cable ties would hold the heater until I discovered and fixed it. Figure, the likelihood of both nuts coming loose and both cable-ties breaking before I realize something's up is fairly remote.

Get Hosed

"defroster unit" installed

From the engine to the Vanagon rear heater / bus defroster is a stretch of a little less than 8 feet. From the prior install, I have 1 meter lengths of 5/8" hose attached to the outlet and inlets, draped into a bucket of shallow coolant. I did a little research and learned that the Vanagon had 5/8" hoses, but there was a section of hose or pipe through the firewall that was only 1/2". There is also a restrictor of some kind that reduces the coolant flow to the rear heater. The theory is that if the rear and front heater units present the same diameter, the coolant will take the shorter path (rear heater), leaving the front of the Vanagon wanting. Well, we don't need the restrictor, but we can use the 1/2" pipe concept. I figure if the original can handle the smaller pipe, and deliver coolant without a pressure issue, we can use the smaller diameter pipe, potentially getting the coolant to the defroster faster. Maybe it will stay that little bit warmer. Ultimately, I had 1/2" pipe and I didn't have 5/8" pipe, so maybe I'm just back-justifying.

pipes in, hoses started

Aaanyway, I cut 2 33" lengths of 1/2" aluminum pipe, wrapped them with pipe insulation and mounted them to the underside of the driver-side belly pan, at least 6" inboard of the diesel heater exhaust. For mounts, I used 1/2" pipe hangers threaded into the bottom of the pan with long Phillips head sheet metal screws. Onto each end of the 1/2" aluminum pipes, I added a short stretch of 1/2" hose, and then a 1/2" -to- 5/8" reducer. At the rear-end (front is front), I attached the 5/8" hoses that were hanging in the bucket, previously used to route coolant from the engine to the heater. At the front end, I ran a stretch of 5/8" from the engine-outlet side to the lower barb, and the upper barb to the engine-inlet side. My thinking was that if there were an air bubble, it would be forced through and back to the engine... or at least down to the bleeder screw. On that, I have been considering how to thread in a short stretch of hose into the bleeder threads in thinking that I could raise the other end above the heater core for bleeding. I haven't pieced that all together yet.

I'll stop here for now. I did fill the system with coolant, opening the various bleeders along the way. I burped out air and then ran the engine for a while trying to get any other air out. We'll see how effective I was. As is, Hapy is drive-able again, with a completely closed cooling system. Next, I need to tackle the register, connecting the heater to the air duct and then wiring up the fan.

As we get deeper into the summer, this project seems less important, but fall feels right around the corner. If we ever get to see live music again, or simply camp in a State Park, having a means of clearing the windscreen hasn't a season here in the Pacific Northwest where the dew point is usually only a few degrees away.

Thanks, as always, for following along. You don't need to believe in CoViD-19 to catch it; you just need to be careless, or be around others who are. Please continue to wear a mask, wash your hands and practice physical distancing for the better health of those around you--