How good of a vacuum do you need?
Posted: Wed Jan 26, 2022 12:49 pm
Been working on restoring my '88 Mustang and adding AC back in using R12. All new NOS Ford lines, and rebuilt the compressor.
Initially I was having trouble pulling a deep vaccum and was having it stall out around 5000 microns. I abandoned the manifold guage and used an Apion VCRT, pulled the core and pulled a vac direct. This setup really works well as it holds both vacuum and pressure for days.
This seemed to help, but I wasn't I wasn't making significant progress, so i decided to introduce some nitrogen into the system. I used the opportunity to leak check as well (no leaks found, pressure would hold steady for days). Each time i filled with N2 and pulled a vacuum i was able to pull a deeper vacuum, quicker. I repeated a couple more times after that and each time was able to get deeper vacuum in a much quicker time.
I'm at the point where I am sub-200 microns, and it will pull down to this pretty quick. Stalls out around 170-180 microns. The issue that makes me think my vacuum is not quite where it needs to be is that when i close the ball valve to isolate the system it creeps up to around 1000-1200 microns and settles out there. it takes several hours to do this, so it will pass a 10 min decay easily.
Do i keep doing what I am doing with the N2 purge/vacuum, or is this good enough? I'd feel better if it stopped around 500 microns (or better) once i shut the vacuum off. I do have the luxury of time here considering it's Jan and the car is not going anywhere for a while
Initially I was having trouble pulling a deep vaccum and was having it stall out around 5000 microns. I abandoned the manifold guage and used an Apion VCRT, pulled the core and pulled a vac direct. This setup really works well as it holds both vacuum and pressure for days.
This seemed to help, but I wasn't I wasn't making significant progress, so i decided to introduce some nitrogen into the system. I used the opportunity to leak check as well (no leaks found, pressure would hold steady for days). Each time i filled with N2 and pulled a vacuum i was able to pull a deeper vacuum, quicker. I repeated a couple more times after that and each time was able to get deeper vacuum in a much quicker time.
I'm at the point where I am sub-200 microns, and it will pull down to this pretty quick. Stalls out around 170-180 microns. The issue that makes me think my vacuum is not quite where it needs to be is that when i close the ball valve to isolate the system it creeps up to around 1000-1200 microns and settles out there. it takes several hours to do this, so it will pass a 10 min decay easily.
Do i keep doing what I am doing with the N2 purge/vacuum, or is this good enough? I'd feel better if it stopped around 500 microns (or better) once i shut the vacuum off. I do have the luxury of time here considering it's Jan and the car is not going anywhere for a while
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