Vanagon Rear Heater Leak fix

No, I don't have a Vanagon. But, I do use the rear heater for my main heater in the bus. In the Vanagon, these sit under the rear seat, and provide auxiliary heat for the passengers back there. I've heard that they do little more than provide a leak in the cooling system and a corresponding coolant smell in the passenger compartment. I don't know all the answers as to why these leak, but I did find one. Today's post is about that, furthering my winter break efforts (See: Planning Winter Break)

Heater Layout

Let's start with some orientation. The heater is a hard plastic shell that is relatively rectangular (approx 12" wide, 7" deep and 7-1/2" tall). There is a snorkel on the front (front is front) that directs the air out onto the floor. On the rearmost part of the right side there is a round hole (about 3" diameter) where the air is pulled in. Passing in front of the fresh air hole are the coolant inlet and outlet lines. The bottom line (return) leaves the heater core, turns 90* and runs rearward. The top (feed) line enters a valve and then turns 90* into the heater core. The core is held in place with 2 Phillips head screws. The valve is held together with 2 7mm-head bolts running front to back.

Possible Points of Failure
I first thought these heater units had all kinds of failure points, but there really aren't that many. There's the core. Sure, heater cores go bad. There are the points where the rubber hoses meet the bibs. There are the plastic 90* bends, but they hardly ever fail, and then there's the valve. Not too many opportunities for issues.

Look Around
If your unit is leaking, look around to see if you can tell where it is originating. Yeah, that sounds obvious, but if you clean it up and dry it off and then start adding distilled water to your system, you should be able to identify where the drips are starting. This is especially true of anything that isn't the heater core. If that's your cause, water will just start appearing underneath the unit. This is an easy fix: buy a new heater core, pull the old one (2 screws), slap in a new one. Still, I'd complete the rest of the post here, just in case.

Start with the Obvious
Okay, so you see some drips over by where the rubber lines meet the unit. Are the rubber lines in good shape? Any cracks or splits? Are they seated all the way on to the flat plastic stop? Are the hose clamps tight? My top coolant line wasn't all the way on, so I thought this was my cause. I loosened the clamp, pushed the hose all the way in and tightened it up. This slowed the leak, but it didn't stop.

Leaving the Valve

Van Cafe replacement valve

The valve attaches to the heater unit with 2 bolts, one above and one below the opening where the coolant passes. If you remove the bolts, you may see that there is no gasket between the two opposing faces. I think this is the spot where many of the Vanagon rear heater leaks originate. The coolant doesn't leak when these units leave the factory, but after years of jostling around, the lack of a gasket eventually takes it's toll and a tiny gap is created. If your valve has failed, and the leak is coming from the valve, (EDIT 2021-Jan-25) GoWesty has a replacement here. The image to the right is the old valve that Van Cafe used to sell. I am unable to find it on their site anymore.

Solved
In classic shade-tree fashion, I solved the problem with a rubber washer from my house plumbing supplies. I took a small dab of Form-a-Gasket to act as a temporary glue and smeared it on one side of the rubber washer. I place the washer on the tip of my pinky finger and stuck that finger into the valve, sliding the rubber washer into the flat face, goo-side first. This centered the washer on the hole. I held it there for a few seconds and carefully removed my finger. The washer stayed in place. I then set valve against heater unit taking care to not bump or in any way shift the washer. Once aligned, I ran the bolts through and tightened the bolts. Unlike when there wasn't a washer, the bolts are unable to mate the faces completely. There is a small gap through which I can see the washer. I initially thought this was not going t hold for that reason, but so far testing has shown that this is holding up okay. I need a longer at-temp road test, but the round-the-block tests have been very positive. Total cost: $0.

That's it for today. If you like throwing parts at a problem, (EDIT 2021-Jan-25) your options are not as plentiful as they were. Van Cafe no longer offers the "replace everything except the plastic" kit I referenced here. I looked on BusDepot and GoWesty as well; options have disappeared in the 5 years since I first posted this. As always, thanks for following along.