Metallurgy Nerd: Mr. Fixit

My father always used to say "I hate buying used cars" and I couldn't agree more. You never know what you're going to get and unlike any box of chocolates Forrest Gump ever considered, it's probably not going to be sweet and delicious, not even metaphorically. If a used car WAS like a chocolate, it would probably be one of those chocolate-dipped candied ginger slices favored by old ladies whose faltering palettes were so dulled by wartime rations that only ginger can provide the startling culinary jolt necessary to register on their tastebuds.

So when I bought my used Jeep Liberty a few years ago I didn't even bother with a mechanic's inspection. I figured I could tell if there were any major problems myself and anything more than that was a roll of the dice anyway. After purchasing it for $6000, I immediately drove it down to a dealership and dropped $2000 having everything fixed that they could find wrong and put in a new clutch just for the heck of it. I figure if it's worth owning, it's worth having everything in good repair.

Fast forward about a year and a half and I noticed that the air conditioning isn't very cold in the Jeep. Since the AC runs 7-9 months of the year here, system failures are common and regular. I got it diagnosed and was told that there was a leak in the cab, which meant two things: one, I've been breathing R134a refrigerant which the crusty old guy at the auto parts store swears will kill you, and two, my evaporator core is shot. The quote to replace the evaporator core is $1100. As usual, most of the cost is labor since the core itself is about $300 but it's buried in the dash and the mechanic said it takes about a day to change it out. But the leak seemed slow and financial concerns outweighed personal health concerns and I opted to buy a few cans of R134a and just charge the system up now and then. I quickly calculated that at $10 a can for R134a I could charge the system once a month for the next 20 years for the same price as replacing the evaporator core. It seemed like the logical choice so that's what I did all summer and much to the surprise of Old Mr. Autoparts I didn't die, not even once. The downside was that the AC was in a state of perpetual mediocrity except for about a day and a half after a fresh charge. I resolved to fix it before the next summer in 2011.

When I first bought the Jeep I had the good fortune to find online a PDF copy of the entire factory repair manual, all 2145 pages of it. I flipped through the appropriate sections of the manual describing replacement of the evaporator core and finding it particularly complex I decided I'd better just pay a mechanic to do the work. In the coming weeks I pondered on the repair job further and it dawned on me that although the job had a zillion steps and required me to dismantle half the interior of the Jeep, it was essentially a giant puzzle with well laid-out steps and didn't require any specialty tools. Having convinced myself that I could do the job at home I started ordering parts. And since I wouldn't be paying a mechanic for labor, I decided to open up the budget a little and replace the compressor and drier assembly while I was at it. The evaporator core was $35 on eBay (they're all made in China no matter where you buy them so why pay $300 at a dealer?), and a genuine OEM compressor and drier assembly kit was about $300. I also bought a digital AC manifold gage ($150) and several cans of R135a ($50) for recharging the system once it was all back together. I already owned a good vacuum pump for evacuating the system before recharging so I ordered a few brass fittings ($10) for connecting it up. For less than $600 I would basically have a whole new AC system and some tools I can use in the future. I figure that getting the work done at a dealership would have cost close to $2500.

With all the parts in hand and tools at the ready, I started the repair work early on a Friday morning just in case I totally screwed something up and needed Saturday to finish the job. It went better than I expected and took me 6 hours start to finish. I think I could do it in 3 or 4 now that I know a few tricks, but with any luck I'll never have the opportunity to improve on my time. After everything was back together and all the leaks identified and fixed I charged the system up with my fancy manifold gauge and that was that. I had one leak show up a few days later but it was just a connection that hadn't been tightened enough. 10 seconds with a wrench took care of it and it's been working flawlessly for several months now.

Pictures of the repair job:

Here you can see the dash has been mostly removed and pushed to one side so I can get at the HVAC assembly that contains the heater core, evaporator core, fan and blend door. There's a zillion wires and vacuum lines involved, but only 6 bolts to get the dash off. I also had to remove the center console, steering column and a few other things to get to this point.