W126 Air Conditioning Woes - PeachParts Mercedes-Benz Forum

hbofinger · #1 08-27-2003, 05:20 PM

Hi all,

I have a leak in the AC on my 1989 560 SEL. I had a conversion done (we knew it had a leak before the conversion), and it held Freon for about 6 weeks before it ran out. Compressor is fine.

I got an estimate from one mechanic putting the damage at about $1,600, from another at bout $1,400 (believe it or not, the lower estimate is from a Benz specialist with a higher labor rate).

I am told the expansion valve is leaking behind the dash, and I also have a bad suction hose. However, the last mechanic who looked at the car (with the lower estimate) was quite blunt: There is hardly any pressure left, I could do the expansion valve and the hose myself without really draining the system since it's basically empty, and then have any shop refill the system. He was actually encouraging me to do this, giving me detailed instructions on how to do the job. The parts seem to be not so bad, but both mechanics basically told me that the job is simply a royal pain in terms of labor.

I see the suction hose in the front of the engine coming in at about $230, and the expansion valve at about $33. In spite of the cost of o-rings, oil, and refilling with R134, it seems I could be saving myself a heck of a bundle if I tackled this myself. And while I am at it, should there be anything else under the dash I should be doing?

Any ideas or advice??? Has anyone done this? The instructions on the CD seem to be a bit contradictory to what the mechanic told me. He said I should remove the lower dash on the driver's side, remove the protective bars, push out the instrument cluster, and then I'd be able to get to it. The CD is talking about removing the cover under the instrument panel as described in process 83-150, but as I look at this, it seems to me that they are approaching the problem from the center, and don't mention anything about the instrument cluster itself.

Thanks in advance!

stevebfl · #2 08-27-2003, 06:04 PM

Not sure why the bill for those parts plus labor would get where you quoted.

The expansion valve can bring tears to the most athletic of technicians but unless you damage the evaporator in the process it does not take a lot of time (a few hours).

If it were my car I might do the expensive hose and bring the expansion valve to a pro. I definitely am long past doing that intense of an under dash job myself.

hbofinger · #3 08-28-2003, 08:47 AM

Seems to me the bill is so high, and one of the mechanics so friendly in telling me how to do it, because these people really don't want to do it themselves!

Thanks for the response. I think I will expand my foul-word vocabulary one of these days and actually do it myself. I do have one additional question, though:

Obviously I am breaking open the system. Does this mean replacement of the dryer/dehydrator (it's two months old, because we did the R134a conversion)?

#4 08-28-2003, 09:51 AM

Henry
Like any job that looks formidable - take a deep breath and break down the repair to many simple jobs. Look at each step of the process as one job - it helps to give you confidence to go to the next step. When all the steps are done - instead of one big job that makes you pull your hair out - you have accomplished many small jobs that seem to make the going easier. That is how I attack jobs like the one you will attempt. I have always been told to replace the drier every time the system is cracked open. For the cost - it is peace of mind and eliminates the possibility of re-doing the job. Remember - when you put in R134 - only use 85% of the charge stated on the car for R12. Just remember to have lots of time for the job - just in case you run into snags. When you have to operate under the gun - frustration sets in and mistakes happen. With extra time available - you can do it leisurely and enjoyably at your own pace. As usual - I speak from experience.
Morris
PS - since my fuel line replacement - idle is still smooth. Had a terrible summer with mine - started with new tire having factory defect and blowing out 2"x3" of the inside sidewall of rear tire at 85mph coming home from funeral in Michigan. Followed immediately by the dreaded broken neck on rad syndrome - followed by defective viscous fan causing overheating (new 3 years ago), followed by defective fuel accumulator and then rear nitrogen cells. She purrs and runs great now. No complaints - maintenace is required on any older car. I still love her!!!
Cheers!!

hbofinger · #5 08-28-2003, 10:39 AM

moedip - Sorry to hear about your bad luck! I had a blowout a few weeks ago, but it was less dramatic, and on the TT, not the Benz. Was going about 8 mph approaching a stop sign, and BANG!!! HISSS!!!! The front left tire went. Living in Washington, D.C., I first thought it was a gunshot (I had the convertible top down). This happened 19,000 miles since new. And this was the SECOND bad tire!

Audi has agreed to pay for a whole new set - I had Bridgestone Potenzas, and all of the sidewalls were bad on the inside. I went with Sumitomos as the replacement.

Also did the timing chain on the Benz, as well as the rails on the passenger side. This was a nightmare. I was smart and removed all rockers, placed them in zip lock bags and labeled them correctly. I then went to work on the chain rails first - the passenger side behaved, but I broke a nut trying to pull one out of the driver's side, and could not undo the distributor bolt. So then I gave up on that side for right now, and rolled in the new chain. Since I had no rockers on either side, and plugs were removed, the rolling in went perfectly.

As I tried to reinstall the rockers, all hell broke loose. The valve spring compressor I used was a real pain, and often snapped out of place. At one point, on the number 1 cylinder, it snapped out of place so badly that the shim/washer/whatever you call it shot out and disappeared. As I began looking for it I realized I had removed the towel covering the timing case entry by the sprocket, and I realized that's were it must have fallen. Oh F*CK!!!! More experimentation and looking at the opening revealed that the odds of it having fallen anywhere else were slim - the was on opening right there on the head that looked like it was designed to make errand shims from No. 1 fall into timing cases.

What do you do? I began thinking - o.k., you just go on, install all of the other rockers, complete the engine as best you can, and then go make a decision - maybe have it towed to a shop to do the timing case, or whatever. So I kept on going.

You have 16 valves, i.e. 16 rockers. At three minutes a rocker, that should take you about 48 minutes to put them all in. At eight minutes per rocker, it takes you over 2 hours! I realized I had to pretty much position the cam carefully for each rocker I was putting in, lest the valve spring compressor would jump rather than giving me the clearance. And it happened again - ANOTHER washer jumped. By this time I had learned my lesson - all dangerous opening were stuffed with rags. I could hear the ringing sound as it fell, and found it right away.

Over time, about three additional washers jumped (I found them all right away in obvious spots), and then it dawned on me - the sound they made when they fell on the block somewhere was always the same. THE SAME SOUND I HEARD WHEN THE FIRST ONE JUMPED! So at 12:40 am, I started looking all over the block like crazy. And I found it - in a deep crevice in the front on the intake manifold. It had never gone into the case!

At this point I knew I would be driving the car out of my friends garage. I was also dead tired. So I went to sleep - on the back seat!

She drives great now, I still need to do the other rails though (I bought some Aero Kroil for the distributor nut, and will have to drill out the broken bolt in one of the pins). And now I need to do that stupid expansion valve! Argh!!!! But I love the car, so I'll do it all....

Thomaspin · #6 08-28-2003, 03:27 PM

I changed the expansion valve on my 300SD (1983) recently - easy to access once you remove the cover under the steering wheel, but the four hose fittings are hard to get at, especially the top left one. A selection of oddly shaped wrenches helps. Also, the valve is wrapped in foam for insulation and mine disintegrated, so I fashioned a new foam wrapper from pipe insulation available at the local hardware store.

I believe replacing the evaporator is much tougher - lots of things to remove.

Check the a/c piece on my site - while I did not illustrate the expansion valve job, some of the other parts may help.

jbaj007 · #7 08-28-2003, 09:08 PM

Look at some crow's foot wrenches before you start...makes the expansion valve removal quite doable.

hbofinger · #8 08-28-2003, 10:18 PM

Crows foot wrenches - bingo!!! That's exactly what I was told by the helpful guy in the shop. Getting a set this weekend. The Benz CD manual even tells you - 17 mm, 19mm, 22mm, and 24mm.

Thomaspin - your site was invaluable. I printed out all of your pictures on my color printer, placed them in plastic protective sleeves, and put the whole thing in a plastic three ring binder. When I did the timing chain, they were my color guide to the job, sitting right on top of the engine, being paged through during the process. Unfortunately my job did not go as well, because I could not pull the distributor bolt, and the pins on the driver's side seemed frozen. In the next two weeks I will revisit this, with plenty of Aero Kroil. Thanks a ton though! Great work!

Thomaspin · #9 08-29-2003, 12:41 PM

Thanks for the kind words. You need to rent a Border Terrier to avoid getting stuck. A source of infinite wisdom and wise counsel.

jay3000 · #10 08-29-2003, 01:32 PM

The one you will really need a crows foot wrench for is the largest one.. It's 22mm, and damn difficult to find.. You can find a 7/8 (same size) crows foot, and grind the sides off of it for more clearance..

Another option is to take a 12 pt. 7/8 box end, and cut the end out of it enough to fit over the metal line.. Might want to cut the other end off to make it shorter, for more turning radius..

It's really not that hard.. Go ahead, and remove all of the bolts holding the black metal brace, so you can move it around.. No need to actually take the metal brace out of the car though..

hbofinger · #11 08-29-2003, 02:44 PM

Jay3000 - Thanks. I actually did a find an entire crowfoot set on the web, going all the way to 24mm, for only about $30, by Astro. OK, so they're not Snap-On or Craftsman, but I will give them a try.

The set is at the bottom of this link

jbaj007 · #12 08-29-2003, 05:07 PM

That looks good. The flare nut style is the perfect type (can't tell from the picture if that is flare nut style), but the flare sets usually only go to 22mm. Here's both types of crow's foot sets (regular and flare) of dubious quality: http://www.jcwhitney.com/catsubpic.jhtml?CATID=4136&BQ=jcw2

1991300SEL · #13 08-30-2003, 07:44 PM

I have a 22mm crows foot purchased at Sears. Can't say that I've looked lately. Do they no longer carry that size?

hbofinger · #14 08-30-2003, 10:14 PM

Maybe they do, but not according to their catalog. Their set only went to 19mm.

It's a bizarre thing - I would gladly have paid $69.99 for a more complete set by them, rather than $30 some-odd for a no-known brand that you don't know if it will hold a decent tourque without bending or cracking.

I've never had a chance to own Snap-On. But I do know that the Sears stuff is unbelievable compared to the rest of the junk out there.

jay3000 · #15 08-31-2003, 08:53 PM

I'm stuck on Craftsman.. The "no questions" replacement policy is just hard to beat for their hand tools..

It might be hard to find the snap-on guy in an emergency..