What was the problem with your R4? In Demothen's case, it was the installer's fault.
There's millions of R4's still running in GM cars. Are you saying they're all trash?

Here's a comparison of the left & right ends of the damaged evaporator (Part #123 830 14 58, I believe intended to fit a Seimens housing) vs the left & right ends of my old evaporator (Part number not known - can't find a stamping and the label is long gone, out of a Behr housing).

Note the 3 crimped tubes on the damaged evaporator. It looks like the evaporator is designed to be parallel in 5 circuits. Meaning that the refrigerant is split into 5 paths, then each path loops through the coil in 3 loops (so 6 passes total per loop, 3 in each direction) making for a total flow length of ~30x the length of the evaporator. Those 3 tubes are all on one circuit, so assuming that they are 100% blocked (not realistic) I would be losing 20% cooling capacity.

Sorry that the pictures aren't all taken from the same angles.

I didn't get a great picture of it, but on the old evaporator there are 2 spots that might be leaks where the 180 degree bends are brazed to the long loops. I didn't bother pressure testing or thoroughly cleaning the old one yet, since I'm hoping not to have to reuse it.

Edit: Looks like my new evaporator should get here tomorrow. Here's hoping it's not damaged. I will get some direct comparison photos and try to fit it once it arrives.

http://www.peachparts.com/shopforum/...evaporator.jpg

A quick data point. I installed Roll Guy's Sanden bracket in my 1985 300D a few years ago. This weekend, I found a big crack. The part of the bracket with the round tubes that envelops the axial hole in the block had broken off. I had wondered what the rattling sound I had been hearing just off idle for a month was, and finally noted it was louder with AC on. For now, I just removed the AC belt and will suffer the rest of the summer (higher priorities). Maybe do a weld repair next spring and beef up the bracket. I am using the smaller SD7H13 on this car, so maybe others will crack sooner, though metal fatigue failure is statistical.

Did you get the Siemens evaporator? Does it have a p/n stamped on it or other markers/ identifiers on it? Does it fit into the Behr housing? If not, what does it take to make it fit?

Sorry to hear that. What gauge steel is used on those tubes and brackets?

Demothen,

Can you take some measurements of the diameters of all evaporator copper tubing big and small? Does the diameter remain the same after it splits from the liquid line to 5 tubes?

New evaporator is in. As feared it doesnt quite fit the housing. I will need to make some templates and take some measurements, but it looks like I may be able to cut out a small area of the housing near where the TXV mounts and move it out by about a quarter inch to make it work. Will probably need more modification where the lines for the TXV pass through the housing as well.

I will get more detailed pictures and measurments when time allows. I have a non-car related project that needs my time for the next week or two, so it may be a bit before I can get back to this.

Will get meaurements at a later date, but if you look at some of the pictures you can see that the copper tubing gets much smaller once it splits to the individual loops.

Got bored sanding...
Input copper line: 12mm splits to 3.5mm
Output copper line 14mm splits to 7mm

Thanks. This explains why there was so much resistance to flow when I was pumping liquid flush and degreasing agents through the evaporator. The tubes are necked down 57% on the 12 mm input liquid line before going through the fin tubes and necked down again 20% as it exits the 14 mm output line. I assume this was done to increase turbulence and dwell time in the evaporator to increase cooling efficiency.

Fortunately, a forum member has offered me a Seimens housing, so I will hopefully be able to use that unmodified, rather than adapting the Behr housing to fit the evap I have.

I did take some comparison photos and did some preliminary test-fits of the new evap in the Behr housing, and came up with a rough plan that might work, should anyone need to make this modification. Here's a few comparisons of the two evap designs, as well as a preliminary idea of what would need to be modified.

The new Evaporator (Part 123-830-14-58) is very similar in dimensions to the old evaporator (Part number not known), except that the port location is slightly different, and it is roughly 1/2" thicker in one dimension. It seems to fit the Behr housing, except for one area near the ports where the fins are interfering with the housing, which would require a small area to be cut out and new plastic to be added to enclose the part. I've drawn a rough idea of the area that would need to be trimmed on the housing in gold marker. I suspect the parts (not shown) that capture the tubing to the input/output ports would need modification, although that was primarily sealed with some sort mastic or similar sealant.

My biggest concern with making these modifications is ensuring that there's adequate and even airflow around the evaporator. The new evaporator is slightly larger, which should help with cooling capability, but I'm not able to model the airflow to ensure that it flows evenly through all parts of the evaporator.

It is correct to worry about the air flow.... that is more important than the relative technical size of the two units...
Just as the bottle neck of any ac system is the flow across the condensor.. this is just the other end of that equation..

On that evaporator it is actually 1/2" longer that the air flow has to go through, which mean more cooling fin contact area. That evaporator is one of the largest I've seen comparing to other makes and models. Which are usually much smaller.


On another note, here are some pictures of the Siemens evaporator box in three pieces with my old evap with deteriorated fins.

http://www.peachparts.com/shopforum/...1&d=1471462437

http://www.peachparts.com/shopforum/...1&d=1471462437

http://www.peachparts.com/shopforum/...1&d=1471462437

http://www.peachparts.com/shopforum/...1&d=1471462437

http://www.peachparts.com/shopforum/...1&d=1471462437



.

Here is a picture of two Siemens Evaporators. They both have the 123 830 14 58 part number on them.

Interesting though, my original Siemens Evaporator is made of copper tubing, aluminum cooling fins and galvanized metal ends. I replaced it because of the fins had deteriorated from all the leaves and garbage sucked into the system plus condensation water mixed in.

The other evaporator I have is all aluminum, except for the input and output tubings. Between the two, there is a significant weight difference by feel.

I don't recall what version I installed in my car.

One end of the Evaporators.
http://www.peachparts.com/shopforum/...1&d=1471464073

Demothen's Evaporators.
http://www.peachparts.com/shopforum/...ld-evaps-3.jpg


.

The 2 evaporators in the pic are both Siemens? P/n of the unit on the right is legible but I can't make out the p/n of the unit on the left, can you? They both have the same p/n?

I believe an all aluminum evaporator of the same size and shape is more efficient than a copper/ aluminum one.