Today's project was a big one. Removing the AC compressor and suction hose so that I can source replacement hoses and a new compressor.
Also removed the expansion valve, liquid line and rubber suction line. You veterans are not kidding--this is one of the most difficult things short of dropping the engine that I think one can do on an R107.
The day began with removing the steering wheel and instrument cluster to gain access to the expansion valve. I used the Factory pullers, this came out in about thirty seconds.
I thought I was going to have to remove the stalks, but there is a plastic piece at the bottom that comes out, allowing the panel to clear the cruise control stalk enough so you can disconnect the electrical connections and oil line.
There's a plastic cover for the cannon plug that covers the female pins, this came off! Fortunately none of the pins came out of their holes. . . I held the whole thing together while I figured out how to reattach the cover.
Once the panel is out it's pretty clear where the expansion valve is located. It's right there in front of you. . . covered not with butyl tape, but what appears to be a custom butyl conformal coating. . . the only way to expose the flats of the fittings was to scrape it off with a plastic scraper and dissolve it with brake cleaner.
Nasty, nasty stuff, made much more difficult by doing it in the inverted Yoga Position with your head just outboard of the brake pedal. ( I didn't remove the drivers seat for this operation.)
The above is a better shot of the expansion valve, showing the blue liquid line.
Finally after about an hour of scraping enough of the stuff was removed to allow a counterhold on the flare nuts so that the copper pipes of the evaporator are not bent. To separate the TXV from the evaporator required a 24mm flare wrench on the flare nut and a 17mm wrench on the body of the valve itself. . along with a pair of two foot cheater pipes to generate the torque necessary to separate these. I inserted the pipes through the gauge opening- the copper tube can move a little to allow you to line up the wrenches.
The suction line came off a bit easier, it uses a 27mm and a 23 (from memory). The Compensating pipe came off with a 17 with no counterhold (you could use a 12, thanks Roncallo!) The sensing end is a coil of tubing that is clipped to the outlet pipe of the evaporator- there is a half pipe shaped channel on the outlet pipe, the coil goes in there, then the clip holds it down.
You can see the filter screen that is in the inlet to the TXV.
With that out and the pipes cleaned of as much goo as I could tolerate, I tackled the compressor. I am grateful to user cwmoser and this thread:
http://www.benzworld.org/forums/r-c107-sl-slc-class/2357665-ac-compressor-replace-ac-delco-15-a.html which reminded me that I needed to buy a harbor freight long 6mm hex driver to get the forward allen screws out.
I don't have a lift so dropping the subframe wasn't really an option. . .I went the radiator removal route. The fan came out with four 10mm headed screws, they aren't M6, they are a lot bigger, must be unique. Once the fan was free I removed the shroud, a pair of 8mm self-tapping screws at the top and the bottom just held in by clips. One spring on each side holds the radiator in.
I drained the radiator of coolant, disconnected the two trans cooler hoses, the upper, lower and overflow tank hoses (large and small) and removed the piece of black plastic trim under the radiator so I could get a floor jack under there. Using about an 18" long 4x4 to distribute the load, I carefully jacked the radiator up and out of the car-- it was sticking pretty tight on the rubber blocks on either side- these had to be pried inward to allow it to move.
On my '78 there are five bolts holding the compressor bracket to the engine-- three M8 with 13mm head-- one obvious one with a spacer in-line at front bottom, and two holding the rear of the bracket to the engine that were only accessible by jacking (and properly supporting with jack stands) the car and using a 3/8" extension with a universal and a 13mm socket to remove them.
I had to rotate the engine with a 27mm socket to get the notch in the harmonic balancer to line up with the lower M8 allen (6mm internal wrenching feature) so I could get it out. I sprayed COPIOUS PB Blaster on these screws-- I hate the smell of that stuff but it really works wonders. I put as much axial load on the hex bit as I could to hold it in the screw head-- then used the cheater pipe to CRACK the screws loose. They were on there with some serious torque.
After a ten hour day of this, the compressor was out and on the floor. This thing is HUGE! I read somewhere that at 4000 rpm it will put out as much as 42,000 BTU. That is three and a half tons, enough to cool a three bedroom house in certain climates. Way overkill in true M-B tradition!
Tomorrow. . . putting the power steering pump, radiator and belts back, reinstalling gauge cluster and wheel so the car can be driven while I order the parts and plan out the reinstallation. . .