Refridge not cooling - possibly restricted line?

Hello all - new the group, but I do have a family member who is a retired technician from a major appliance retailer and repairer... and even he's stumped on this one.
I have a 1997 upright freezer and a 2002 top-bottom freezer/refrigerator with the same problem: Both have worked fine for several years, until earlier this summer. Both are now Not cooling AT ALL.
Compressors come on, run fine, get very hot, not noisy. Lo side refrig lines and evap coil inside are same as ambient temp. Compressor, hi side refrig lines, and condensor coils (in side wall) are very hot. Checked freon with charging cylinder and guages. Vaccum pumped out all the freon and recharged with amount listed on service tag.
No change.
Replaced drier. Recharged with proper amount of freon. No change. Replaced compressor. Recharged with proper amount of freon. No change. Added additional freon. No change, maybe even got worse.
When both lo and hi sides are equalized, the compressor wil pump up the high side to about 150 psi and pull down the lo to about -30 psi. After running like this for about 15 minutes it has produced nothing but a very minor amount (about 2 inches) of frost on only the cap tube inside the evap. coils. When unplugged from this state, the pressure takes about 4-5 hours to equalize on its own. We were manually bypassing the compressor through the gauges to get it to equalize faster.
Since this was happening with both the old and new drier and old and new compressor, do I have a restriction somewhere in the coils? Has there ever been any urban legends about people having any success removing restrictions? Any secret techniques?
Thanks! Samster2.0
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The clue is that the low side pumps down to -30. That's a good sign of a restriction in the line, some where. Most likely the capillary tube, which is the smallest diameter part of the system. For the ammount of work you have into the system at this point, you could have bought a used refrigerator which is known to run. I know of no unclogging secrets.
--

Christopher A. Young
You can\'t shout down a troll.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.