Air Conditioning for my Diesel SL - PeachParts Mercedes-Benz Forum

mach4 · #1 04-05-2013, 07:16 PM

I decided to try to put A/C in my OM617 powered SL. I knew right from the start that the stock R4 setup wouldn't work, so I relegated A/C to a Phase II project. It was clear that the compressor would foul the subframe.

I watched with great interest the work that Rollguy did on his Sanden brackets for the 617 and 616 engines (http://www.peachparts.com/shopforum/diesel-discussion/320985-installing-sanden-compressor-617-looking-all-options.html) hoping against hope that the setup would work on my project.

I spent countless hours gazing at the space I had trying to figure out whether the compressor would even fit. Sometimes I felt that it would, other times I was convinced that there was no way.

Mostly I was convinced that it would not fit and therefore contemplated numerous alternative solutions. One was to eliminate the P/S pump and mount the A/C compressor where the P/S pump is and replacing it with an electric P/S pump. There are many European cars that use this system as well as the Toyota MR2 over here. I also considered using a hydraulic pump to drive a hydraulic A/C compressor (very common on heavy equipment that have hydraulic systems with lots of excess capacity). Then I considered mounting the P/S pump down low and the A/C compressor up top. There are many P/S pumps that are quite small that would fit in the lower position without any problem. This seemed like a lot of fabrication, so I decided to find out for sure.

To do so, I pulled the cooler lines and the P/S pump which gave me enough room to snake the compressor in the hole. Well surprise, it went in - not a lot of room to spare, but at least it would go.

Here's the first trial fit

It's impossible to show, but there were some clearance issues that would need to be resolved. The first one was an unused mounting tab on the 617 preventing getting the compressor mounted close to the engine. So I just cut it off.

In order to get a better look at where I was at, I fabricated a facsimile of Rollguys Sanden bracket out of 14ga sheet metal so I could evaluate things a little closer. I clearanced the bottom of the plate to miss the ribs on the upper oil pan and this allowed the bracket to move almost an inch tighter to the engine. I welded on some tabs for the compressor and did a trial fit.

Crap. I got totally blindsided. While I had enough (barely) clearance between the engine and the subframe and fender, the pulley was scraping on the sway bar.

So my first thought was that I would need to fab up a bracket to move the sway bar down about 1/2 inch or so. Not a difficult task, but one I hoped to avoid having to do.

After thinking this through a bit I jacked up the car to extend the A arms to their fully extended position. This would be the position of the sway bar under maximum upward deflection. I determined that all I needed was to move the compressor mounting tabs up about 1/2 inch. It's a little dicey since there is not a whole lot of metal on the rearward tab to weld to. It still made a bit of contact, but if I either change the angle of the backing plate, or add 3/8" to the bottom mounting tab, I get the clearance I need.

I will need to clearance the subframe just a bit as shown to gain a bit of extra clearance, but that should be rather easy.

I felt that I would be able to use the design of the GenII bracket that used the compressor swing to tighten the belt, but alas, I'll need to use the essential design of the Gen I version with the idler pulley, albeit with many modifications and changes. The GenII is close, but the extra width that the adjuster brackets take up will definitely hit the subframe. With the GenII setup, I can clearance the unused mounting ear and gain just a bit more room.

Also, if I use the Gen II style, I can add some upper support brackets to add some needed support.

More to come.

mach4 · #2 04-07-2013, 12:18 AM

Made progress on the A/C project today. I'm still working on a prototype bracket using lightweight sheet metal. The first step was to mock up the standoffs that provide the bulk of the rigidity of the bracket and remount the bracket in the car. I pulled the engine again today, got it pressure washed and the plate mounted and reinstalled it in the car. I was very close, having picked up clearance to the sway bar but still hit the subframe when the compressor was pulled into a tensioned position. I clearanced the subframe, but it turned out I didn't need to after all. The real solution was to cut the rear bottom outboard ear off the compressor which gave me exactly what I needed. The bad compressor I'm using for mockup purposes has the top hose connectors which were hitting the standoffs, so I just cut them off. I'll be using a rear exit back plate for the production compressor.

In the first post, I talked about considering tieing into the chain locking screw, but after reconsidering, I'm going to tie into the P/S pump lower inboard mounting bolt. I'm planning on using a shortened tie rod as a base and running between the P/S pump and a sleeve I'll fabricate and mount between the outboard two ears on the compressor. In fact, I shortened a tie rod today and cut off the joints leaving just a threaded end to weld to. I don't know if this strategy is possible on a 123, but because of my custom oil cooler hoses, I've got plenty of room.

The belt from the 107 A/C turns out to be the right length and allows final configuration testing.

A little more research and engineering and it will be time to fabricate the real bracket.

Here's the current setup.

mach4 · #3 04-08-2013, 01:13 AM

Today's efforts involved fine tuning and testing a final design. My goal all along was to try to use as much of Rollguys bracket as possible. Based on the most recent mock up, it appeared that I could move the compressor mounting tabs back down to their "regular" position. If so, then I could use the jig welded bracket as a foundation for my system. I also took the time to fab up a shortened tie rod for a top adjuster and support element.

Here's where things stand. I've got the clearance between the pulley and the sway bar and clearance between the rear of the compressor and the subframe.

In addition, the tensioning/support system gives nice triangulation in the plane of the belt.

Time to fabricate the real thing and start thinking about hoses as well as finding a good compressor.

mach4 · #4 04-10-2013, 10:27 PM

I abandoned the idea of using a shortened tie rod for my adjuster, mostly because the clamp ring hit the vacuum pump housing. So after much investigating of alternative solutions, I hit on the idea of using Heim joints instead.

This is what I came up with.

And here it is mocked up on the engine.

And ready to install

I'm thinking it looks a lot better and should be plenty strong.

charmalu · #5 04-11-2013, 12:57 PM

The Tie Rod looks kind of clunky and bulky. this new design using the Heim Joint
looks more like it belongs there.

I think the Hot Rod guys use these in their projects.

Charlie

Simpler=Better · #6 04-11-2013, 01:05 PM

Slick

I like the heim joint setup much more

mach4 · #7 04-11-2013, 01:14 PM

Quote:

Originally Posted by Simpler=Better

Slick

I like the heim joint setup much more

I call it my Gen II version, where Gen I never "shipped".

Sometimes it just takes awhile to figure out the right solution.

mach4 · #8 04-14-2013, 12:59 AM

Got Rollguy's Sanden bracket in - that's one fine piece of fabrication. You guys that have the room are lucky you can just "bolt and go".

I'm not so fortunate, so I've got some modifications to do before I can make mine work. The first mod was to cut off the sleeves. Next I needed to cut down the standoff's where the bracket mounts to the block to move it closer. Then, because it's closer I've got to clearance where the blue arrow is. Then finally weld the sleeves back onto the plate on standoffs.

I also picked up bolts and sleeves for the new adjuster mounting on the compressor, as well as a longer bolt for the Power Steering pump bolt where I mount the adjuster.

Once everything is welded up I can do a final test fit using my bad compressor and then order the rest of the components to get this project wrapped and the car back on the road.

t walgamuth · #9 04-14-2013, 07:12 AM

As usual your work is impressive.

I gotta say It though, whatcha need AC in a ragtop for?

Oh well, it will make the car more sellable probably and I know you are up for the challenge of it all.

Beautiful work as usual and excellent documentation for the rest of us.

mach4 · #10 04-15-2013, 05:22 PM

I'm almost there with getting things to fit with the compressor. I've got a little clearancing on the subframe yet to do, but the bracket is essentially done.

Here's the top view showing the standoffs for the main 1/2" support bolt.

Here's the back of the plate showing how the three mounting points have been shortened and the clearancing required for the block.

And here's my goofy test bracket that was used to test for clearance before ordering up the Rollguy bracket. Don't laugh - it fulfilled its purpose.

Got the compressor ordered as well as the hose and fittings. I elected to go with the SD5H14 with a K head, which is a SD508 replacement. I may have a hose clearance issue with the compressor mounted vertical, but if so I can rotate it 90 degrees and because of the tilt of the bracket, be well under the 90 degree limit for positioning.

I'll pop the engine out in the next couple of days to do the subframe work as well as pull the driveshaft to replace the spline boot, then it's back in with the compressor mounted and get it vacuumed and charged.

DeliveryValve · #11 04-15-2013, 06:25 PM

Nice work so far. Are you cutting and welding subframe for the clearance. If so you might want to beef up the lower control arm mounts with more gussets.

.

Squiggle Dog · #12 04-15-2013, 06:56 PM

I enjoy reading your posts on the diesel SL and that you are sticking with it. If I had an SL, it would have to be a diesel.

mach4 · #13 04-15-2013, 07:46 PM

Quote:

Originally Posted by DeliveryValve

Nice work so far. Are you cutting and welding subframe for the clearance. If so you might want to beef up the lower control arm mounts with more gussets.

I've already got the gussets welded in. The clearancing I need is like 1/4 inch or a bit more right where shown below. If the compressor were 1/2" shorter I'd be ok. In fact, if I were sure there would be no belt stretch, I'd probably be ok as is.

The current plan is to just make a slit with a cutoff saw, pound it in a bit and then weld it back up. As over-engineered as these things are (with the exception of the LCA mounts) I should be ok.

mach4 · #14 04-18-2013, 09:22 PM

Got the subframe clearanced today. I went ahead and made a single cut and then pounded the metal in to get what I needed. Before welding it up, I put the engine back in, mounted the compressor and verified that I had what I needed. Here's the clearance I have with full operating tension on the belt. Plenty, including some for anticipated belt stretch.

So I pulled the engine welded it up and painted it. I used a gloss black, and the shininess makes it impossible to see what it is. I retouched the image to make it representative.

Also got the oil cooler line support bracket fabricated.

The compressor, lines, fittings, refrigerant and dryer are all in, so after cleaning up the engine compartment, I'll put the engine back in for the last time and get all the lines mocked up so I can have them crimped.

mach4 · #15 04-25-2013, 04:21 PM

Well, I think I can close out this thread. The engine is back in and hooked up. Got the compressor set up, hoses installed and charged the system with Envirosafe refrigerant.

The charging process was a little challenging, but I'm blowing good cold air and everything seems ok.

I won't know for certain until we get some hot weather and log some hours on the setup, but for now, mission accomplished.