As compressors age they get louder as parts wear. Luckily as people age our hearing gets worse.

OT can make hissing or gurgling sounds, knocking is the compressor not the OT

It's not that a #12 hose wouldn't help, it would. It would make the system perform slightly better. But 5 psi pressure drop is great, if I saw that much drop in a current program I would think it's just fine. I can't recommend all the extra work and cost for you just to get maybe 2 psi better. I thi...

5 psi drop is not bad at all, especially with your very highly superheated suction gas. No need for #12 hose, isn't going to improve this situation, and I'm gathering changing it would be a pain. Suction hose size isn't really your bottleneck after all. TXV superheat setting as originally thought co...

That's an Egelhof valve, I used them back in early 2000s. I machined an adjusting tool with a plastic bushing that would mate with the round portion of the body and a single pin. Drilling would be dicey, the spring is inside a recessed bore in that brass piece, the brass is kept to a minimum thickne...

Front and rear TXV is OK, it's just a bit more difficult because of feedback problems. Both TXVs have control over not only their own superheat but also the suction pressure in the shared suction pipe, and they are both also influenced by suction pressure. Two TXVs tend to find conditions in which t...

there is an exposed bias screw on the bottom of the block (end opposite the head). Turn CW in small increments (increases bias spring compression), while running the system is best so you can take measurements and calculate a superheat. The screw is O-ring sealed, driven usually by a metric hex wren...

Now that I think about it, could also be pin leakage in your H-block TXV, does exactly the same thing, test it for internal leakage 1st. A very tiny leak is ok, but if it has a pin o-ring that is disintegrated you could get a short circuit there if the pin/bore fit is loose enough

Way too many unknowns for me to be able to guess.

Yes, and sorry to deliver the bad news. Evaps can have a manufacturing defect that allows an internal leak from the inlet side to the outlet side. Most people think the inlet of an evaporator is mostly liquid, a lot of textbooks call it a low pressure liquid, it's just not true, there is a tiny amou...

I had an 88 Dakota with a 3.9L, AC worked very well, but was a standard cab, tiny interior. My evap was running below or close to freezing I think because i would get a faint mist coming out of the vents when conditions were just right. I think the airflow was pretty low compared to current trucks. ...