Yes, it is 20 degrees in Chicago this morning and yes I am working on the Air Conditioner of my 114 project. This has turned into a big case of "while I am at it...."

How long should an AC system hold vacuum? I have read 20 minutes, 30 minutes, and overnight.

I pulled mine down to 26 last night, and it was still at 26 4 hours later when I went to bed. This morning it is was about 21.

Good enough?

Depends.

Is the leak with your equipment or the system?

Any degradation of the vacuum indicates a faulty system. I'd be suspicious when the vacuum drops overnight.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

If you could only pull 26 inches and you have a good vac pump, then you have a small leak..

I have a vac pump that I attach a hose to the high side port and put the end into a glass of refrig oil..if you have a leak, the bubbles can be seen in the oil...there should be none if you have an evacuated system..if bubbles are evident every 5 min or so, you are sucking air into the system.

If you can get a good vac reading, then close off the vac system from the cars system overnight..[ this eliminates any leaks that may be in your service equipment] then, the next day pull a vac on just the line and pump to evaacuate that..then open the valve to the cars system..the vac reading should be the same as it was the day before...around 28" is Ok and what I look for..that will require a decent vac pump and some evacuation time.
Don't expect to pull a good evacuation in 5 min............

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A Dalton

Thanks for the answers. I am pretty sure I have a leak in the system. Does anyone know of a way to check for leaks with out filling the system?

My problem is that the engine is not in running shape, and won't be until after the paint is done. IT looks like the engine running is required for testing the system with a UV dye.

You can look at fitting and such for evidence of oil..thighten any up that do look like a possiblility..
I would then evac the system and put in 1 can w/dye and just let it sit.
The system will then have equal pressure on it without running the engine.
When you run the engine, the low side actually has less pressure than when the car is just sitting with a/c off.. then look for dye in a couple of days...if you do not see any, then add some more.

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A Dalton

Thanks for the suggestion. I will give that a try.

As Dalton said, you should be getting 28 inches or a little better for vacuum. When starting with an open system, it can take a while to bring the vacuum up.

Th vacuum will not rise to the highest level until the moisture has evaporated, this can take a couple of hours.

What are you using to evacuate? A pump or a venturi?

You can close off te equipment on the W114s by closing the valves on the York compressor. This will help isolate he sysem from the evac equip.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

I am using a 2cfm pump. I think my gauges are shot - they are only 40 years old so I guess somebody got their money's worth. I ordered a new set, shot in some dye, and I will see what shakes out.