Well, the past couple weeks have been busy for me. A while back to replaced the guide rod subframe bushings, trying to eliminate an occasional shimmy. No luck there; I'm going to try tightening up the front wheel bearings, but I suspect it may just be the rims too far out of round. I also managed to fix an electrical problem. It'd been blowing fuse 15, and there'd been a parasitic power draw. In investigating, I found the power seat relay was continuously energized, the dome light was always on with key on if it was in the "on with door" setting, and the seat belt light would flash continuously. It turns out most of the problems went away once I figured out that the supply pump was what was blowing the fuse and disconnected that. I replaced the motor in the supply pump, and all works normally now; I'll probably create a thread on that when I get to it.
Anyway, the two most recent big jobs have been replacing all the hoses and a few other part going to the "fuel package" (the assembly in back with the fuel pumps and filter) and getting the AC going again. I'd noticed some fuel leaking a while back, and hadn't driven the car much because of it and the electrical issues. I had most of the hoses already, so I decided to take it all out and go through it. I replaced the fuel strainer, all the rubber lines (which included new crimped hose assemblies), the rubber mounts, most of the copper rings (you need the 12x16 rings for that). I mostly used Cohline hose, but the one piece from the elbow to the first pump was CRP. Only use Cohline hoses; the CRP hose appears to be cut-rate stuff, but fortunately it's not pressure bearing. Also note you'll have to cut a crimped clamp on the return line – just replace that with a fuel injection rated clamp. You could probably DIY the crimped fuel hoses by buying a couple feet of 14mm ID fuel hose and taking that and the metal pieces to a hydraulic shop. I can't say for sure on that, or if it's worth the cost, but I'll probably see if I can re-do the old pieces. Whatever the case, you're likely to encounter leaks back there at some point, so it's something to at least check along with the under-hood hoses. In the end it's good peace of mind to know it's all been done.
Moving on to the AC, this is probably more lessons learned than success story. The system was converted to R-134 back when, then R-290 when I got it, and after that leaked out, I replaced the drier and went back to 134, which had mostly leaked out over the last couple years. I decided to re-seal the compressor – the most likely source of leaks since I'd already replaced most of the o-rings. I ordered a kit from centuryautoair.com, which arrived quickly, and I believe was Denso parts. Now the first problem: the Gen II V8 cars use a Denso 10P17C compressor. I found a few references to the 10PA17C here, and there was a "17" cast into the case, so that's the kit I ordered. Do not repeat my mistake: if you've got a 420/560SE(L) or 560SEC, you need the kit for the 10P17C. The big o-rings were slightly smaller (I got them to fit) and the seal is a different type. Tearing down the compressor was relatively easy. First I made a plate to cover the suction/discharge ports, as you can see, so I could thoroughly clean it. I washed all the internals with brake cleaner and blew them dry with compressed air. I found signs of contamination, but no major signs of failure. Rather than ordering more parts for a dubious compressor, I jammed the incorrect seal in just to see if it'd hold. Surprisingly, it held pressure, and quickly pulled and held a vacuum when I put it back together. So I charged it yesterday, and here's where I've got problems. It works, but the compressor makes a growling, sort of high-frequency hammering sound when it engages that gets quieter but doesn't completely go away. It's noticeable enough to be disconcerting, but not loud enough that I'm afraid to use it for the time being. So, I'm taking chances, but the system probably needs major attention either way.
My advice on the fuel stuff is to do it soon if it's original and/or you see cracking or any signs of leaking (obviously tighten the clamps first to eliminate that). On the AC, my suggestion would be not to waste time with half-measures. On a high-mileage car that's got a mostly original system, and/or one that's spent some of its life in an unhealthy state, just bite the bullet and drop in a new compressor, drier, and o-rings at a minimum, along with a thorough system flush. If you've got lower miles and a system hasn't seen several recharges and such, that's where I'd consider pulling the front cover and replacing the front o-ring and shaft seal. I'm thinking unless the middle or back of the compressor show signs of leaking, it may be best to leave well enough along. In my case, if the noise doesn't get worse, I think I'll see if I can limp through the rest of this summer. I'm able to find R-12 for sale on Craigslist, so my plan is to accumulate enough of that, get a new compressor, and eventually deep clean and set the system back the way Mercedes intended it. If I'd done that in the beginning, I'd have saved a lot time, along with $200 or so I've nickeled and dimed on it so far.
