It’s February and it’s ten degrees in Boston. And I’m writing about resurrecting the air-conditioning in an E30.
When I bought the 1987 E30 325is back in August 2014, among the things on the to-do list was addressing the fact that the air-conditioning didn’t work. I hooked up my nitrogen tank, pressurized the system, sprayed Big Blu leak-detecting soap solution at every a/c component and joint I could reach, and found a bad leak at the receiver-drier. I located a replacement drier, put it in the E30’s trunk (my strategy to prevent parts from getting swallowed by the anarchy of the basement and the garage), and then largely forgot about it because the car basically sat in storage for much of the next eighteen months.
I pulled the car out of storage just before winter and gave it a coveted space in the garage so I could do the prophylactic timing belt replacement. A few weeks ago, I mentioned that the E30’s compressor belt had to come off in order to replace the timing belt. I fully relaxed the tension on the compressor belt and still couldn’t get it off. I suppose I could’ve simply cut the belt, but since I would’ve been faced with the same issue getting a new belt on, I unbolted the compressor from its mount instead. I thought I’d take that opportunity to undo the compressor’s hoses so I could pull it completely out of the car; turning a compressor upside-down, draining it, and refilling it with oil is the only way to ensure that it has the correct amount of oil in it (compressors don’t have a dipstick).
Not only was the compressor completely dry of oil, its clutch was junk. Clearly I needed a new compressor.
I found one locally on Craigslist for $20, yanked out of a recently running E30 with working air. When I drained that one, nothing nasty came out of it. I didn’t know for sure whether the E30 had ever been retrofitted with R134a, but since the compressor didn’t have R134a adapters on it, I assumed that the car had never been converted. So I filled the compressor with mineral oil (what you’d use for R12), and installed it and its belt before buttoning up the E30’s alternator and power-steering belts. I thought I’d simply install the new drier, put fresh O-rings on all the disconnected hoses, connect the hoses to the compressor and the drier, leak test the system again, and then sit back and wait for warm weather to evacuate and recharge it.
HAHAHAHAHAHAHAHA—oh, God, that’s funny. (Or, to quote Kill Bill: “You didn’t think it was gonna be that easy, did you?” “You know, for a second there, yeah, I kinda did.”)
The longest chapter in my first book is about air-conditioning. In that chapter, I describe in detail the steps you need to go through to resurrect a long-dormant a/c system. Long story short, if a system has sat sealed up, and if it hasn’t suffered any catastrophic failure, and if you’re not changing from R12 to R134a, you might be able to get away with what I was hoping to do with the E30—simply replacing the leaky component, installing a new drier, leak-testing, evacuating, and recharging—but if the system has been opened up, or if some component barfed up its innards and spread them throughout the system, you need to flush out every component and hose.
Now, my E30’s a/c had not sat open, and other than the bad compressor clutch, I was not aware of any catastrophic failure. So it was almost as an afterthought that, as I was about to re-connect the compressor lines, I looked into the hose fittings with a flashlight, and saw, unfortunately, a whole bunch of visible crud.
The high-pressure discharge line coming out of the compressor connects to the condenser in front of the radiator. The output from the condenser goes to the receiver-drier, connected by a small hose. I removed the old drier, tied a paper towel in front of the end of the hose from the condenser, and blew compressed air from the compressor into the hose. When I looked at the paper towel, I saw that it had caught a spray of fine black particulate matter.
That’s not good, but it’s not fatal. On Fords from the 1990s, there was an a/c malady called “The Black Death,” in which the Teflon seals in the compressor would fail and combine with the refrigerant and oil to produce a nasty black sludge that no amount of flushing can reliably remove. The only reliable remediation of cars so affected is replacement of every component forward of the firewall—condenser, compressor, hoses, drier, everything. Fortunately, the fine particulate matter I was seeing wasn’t oily like the Black Death.
If the hoses were clean, flushing them would only be necessary if I were changing refrigerant. However, since these hoses had particulate matter in them, they needed to be flushed out regardless of whether I used R12 or R134a. As it happened, the other thing I noticed was that the original receiver-drier (left in the photo below) did in fact have an R134a adapter on it. Compare it to the new drier on the right, where the fitting is an R12 threaded-style fitting. This made it likely that the system had, in fact, been converted to R134a at some point.
Taking all this together, I would’ve been in an active state of denial if I did not disassemble the system and flush every line and component.
I decided to try the inexpensive measured approach: flushing the system out with mineral spirits followed by non-chlorinated brake cleaner, and re-using the evaporator core and condenser, but replacing the expansion valve.
You can spend several evenings reading up on the pros and cons of flushing a/c lines and components, but here’s an easy way to think about it. You know your car’s dirty brake calipers? You think you’re going to clean them just by blowing compressed air at them? Some sort of solvent is usually necessary and appropriate. Basically, flushing out a/c lines and components is no different than cleaning anything else, except you can’t reach the insides.
Professional shops have closed-loop machines that pump specialized solvent through a line or component over and over, but the DIY-er has, at best, a compressor and a flush canister that sprays a flush chemical (some sort of solvent) through a wand that’s inserted into one end of a hose, line, or component, and the solvent is collected as it comes out the other end. Then it’s a question of the choice of the solvent; you can buy specialized a/c flush chemicals, but they’re not cheap, so some folks use a variety of conventional cleaning solvents, trading off low cost against their toxicity and flammability.
I personally don’t ever want to spray acetone (toxicity) or lacquer thinner (flammability), so I use mineral spirits, leaving the garage door open and keeping a fire extinguisher handy, followed by garden-variety non-chlorinated brake cleaner, chased by compressed air. Part of the appeal of mineral spirits, supposedly, is that, if you’re running R12 refrigerant, you’re using mineral oil as the lubricant in the a/c system. Mineral spirits supposedly are chemically compatible with mineral oil, so trace residue of mineral spirits isn’t a contaminant in the same way it would be if you were running R134a and lubricating with PAG oil, but whether that’s really true or not I don’t know.
The problem is, you can only flush a line, hose, or component if you can access both the input and output ends, and if the component flows freely from input to output. You don’t flush through a compressor; you fill it with the proper oil and drain it and refill it—repeatedly. You don’t flush through a drier, you replace it. You can flush through the condenser and the hoses plumbing it, but you can’t flush through evaporator core because the expansion valve is in line. So if you suspect contamination, you have to disconnect the hoses from the evaporator assembly, pull the assembly out, and remove the expansion valve. Then you can lay the evaporator core on the ground and flush it. And with the hoses disconnected, you can flush the hoses.
Now, flushing with solvents is nasty, smelly business. With all the issues of toxicity, and flammability, and the possibility of the solvent damaging paint or interior surfaces, I don’t recommend that you do it. But what I do is pull on a Tyvek suit, add rubber gloves and full-seal goggles, and use a pressurized flush canister and a standard pistol-grip air gun with a rubber tip. If the inlet tube of the hose or component is larger than the air gun’s rubber tip, I hold the rubber tip tightly against the inlet tube so it seals as well as it can, then wrap a rag around the joint so that if the seal is incomplete, the spray doesn’t hit me in the face or shoot across the room. If the inlet is too small for the rubber tip to seal against, I take off the rubber tip and jury-rig a piece of rubber hose of the appropriate size (often a ¼" fuel line) and clamp it securely in place at both ends with hose clamps. I do the same thing (hose and clamps) at the other end to guide the waste liquid into a catch bottle for later recycling.
It’s one thing to flush out a condenser that’s mounted in the nose of the car, or an evaporator core that’s lying on the garage floor, but it’s a little hairy blowing out the lines leading from the passenger compartment into the engine compartment, because you really don’t want a bad seal or a loose hose to spray solvent all across your interior; it’s very likely to discolor anything dyed.
I run long hoses with hose clamps connecting the end of the air gun to the inlet of the line I’m blowing out. This lets me have the actual air gun and solvent canister sit on the floor of the garage instead of inside the car. Then I position a catch basin, like a paint tray, inside the car, underneath the hose’s connection to the line to catch any drips, and wrap the joint in a rag for good measure.
As I said, not for the faint of heart.
Getting the E30’s evaporator core out wasn’t trivial, but it was much easier than the older cars I’m used to. On a 2002 or a 3.0CS or a Bavaria, the evaporator assembly is a two-piece plastic tub with the top clipped. The entire tub has to come out of the car; then you have to pop off the clips holding top to bottom and disassemble it in order to pull out the expansion valve so you can flush through the core. Mercifully, on the E30, there is no “tub.” Instead, the evaporator core and the expansion valve slide out of a compartment. I followed instructions on a few E30 forums to expose and then remove the evaporator core. None of them listed having to remove the trim pieces around the base of the console. I managed to get the evaporator core out, but when I reinstall it, I’ll pull off the trim so I don’t damage anything.
Before the temperature plummeted, I donned the Tyvek suit, the gloves, and the goggles, opened up the garage door, and did the Big Flush. Now I’m waiting for the new expansion valve to arrive so that I can begin buttoning things up.
Because it’s February and it’s ten degrees in Boston. Because timing is everything in life. Unless this is just simple masochism.—Rob Siegel
Rob’s book Memoirs of a Hack Mechanic is available through Bentley Publishers, Amazon, and Bavarian Autosport—or you can get a personally inscribed copy through Rob’s website: www.robsiegel.com.
