They asked for 8-12 hours of labor to do a full diagnostic, at $167/hr. So, $2k just to find out what's wrong and what it will take to fix. After he saw the bus and engine, the guy I'd been corresponding with walked me through some of the possibilities, and I bluntly asked "what's the best case scenario?". He described a couple of the simplest things that might be wrong and need doing, including just replacing the head gasket. In those best case scenarios, he said the total cost would come out to around $5k. Then there are the non-best-case scenarios, where I spend $2k just to find out that I need a new engine that's going to cost $15k to buy plus $15k to install.
I don't think proceeding down that path is financially viable. $2k is enough to buy another bus. $5 is enough to buy two buses, or one and get it thoroughly looked over and maintained for a while. $30k... is enough to just buy a vehicle with a warranty in the first place.
So, here's the plan.
I will continue living in this bus for now. I aim to drive it back to San Francisco, probably at night for a cooling bonus. I'll keep parking it in my 3 favorite spots near work, moving it every 3-7 days. I've got my fingers crossed that it will start and run for those few minutes every week for a while.
I will look for opportunities to get rid of this bus. I'll be taking some photos to post on Craigslist and elsewhere. Maybe someone wants it for a stationary tiny home. Maybe someone wants to keep it in their driveway and rent it out on AirBNB. Maybe some enterprising diesel mechanic wants to spend a few weeks and $10-20k and get a well-running bus out of the deal. I'm going to ask a few scrappers what they would give me for it, as a last resort, and that should be a decent amount because it's mostly aluminum.
I will keep working on living-space improvements that I can take with me to another vehicle, like the kitchen cabinet plumbing, generator housing, etc. Once I narrow down the most likely ways to get rid of the bus, I might also make a few more improvements that increase its resale value.
I will start (well, continue and accelerate) shopping for another bus, or possibly another large vehicle. There was a whole fleet of buses in Livermore earlier this week that sold for decent prices; sadly they were all 40ft which is longer than I want. If I get another transit bus it will probably be ~29ft, or maybe another ~34ft. I will revisit my decision regarding vehicle types, and reconsider school or tour buses. I'll also consider "shuttle bus" type vehicles, the kind built on a large truck chassis; I didn't hate my ambulance and there are significant maintenance cost benefits to be had by downsizing to a vehicle that more typical mechanics can work on.
If I get rid of my bus before I find a new one, I'll be spending some days or weeks hopping between local hostels and co-living spaces. I'll stay at the Embassy again. I'll stay at the Red Victorian (where my board game collection is currently living). I'll probably stay at Green Tortoise as well. Anyone who wants me as a houseguest in the bay area for a day or a week should speak up.
That's all for now. More to come, re selling and shopping and starting over!
PS: It turns out that it's possible to put the engine on jackstands, unbolt it, and then lift the bus around it, effectively lowering the engine enough to work on the head and cylinders without fully removing/detaching it from the bus, and without a maintenance pit. Sadly, this revelation didn't make the prospective costs much less, but it's useful info in future vehicle purchasing decisions.