Purchased this OMT RS-1.5 vacuum pump brand new 11 months ago. 3 months later, I used it for the first time. Had to rebuild the A/C compressor on my 1987 Toyota 4Runner and I was ready to evacuate the system after the repair.
I could not get vacuum stronger than 22 in.-Hg. Didn't know if it was my gauges leaking or possibly something on the 4Runner, but I let it run for a long time then went ahead with charging it up with R134a. The A/C still works great here 8 months later.
Yesterday, I tried using this vacuum pump for the 2nd time ever. This time, following replacement of the evaporator on my 1994 Toyota Pickup 4x4. This pump still will not pull more than 22 in.-Hg of vacuum on the gauges.
I tried removing the low-side hose from the manifold and replacing it with a metal cap, which isolates the vacuum to just the manifold, the low-side gauge on the manifold, and the hose between the manifold and the pump. I even put Nylog Blue sealant on all of the hose connections of the manifold gauges, and the hose that connects to the vacuum pump inlet. This is with the pump full of oil, the oil is still clear and not turbid/milky looking. Nevertheless, I STILL could not get better than 22 in.-Hg.
Everyone on the internet says I really need to be getting like 28~29 in.-Hg to evacuate the system properly, but unless OMT helps me out or I just shell out more money for another pump, it ain't happenin' for me. Hopefully it's not that big of a deal to only get 22 and/or OMT reaches out to correct this, cause the actual A/C repair job is enough work by itself, and adding repairing the tools to do the job is just ridiculous.