Why Is My Vacuum Pump Not Successfully Pulling/ Pumping Down?

People tend to point fingers at or suspect the system vacuum pump when the system is not creating an adequate vacuum. Troubleshooting other parts of the machine is frequently what causes the vacuum pressure to drop. There is an old saying when dealing with any vacuum system, “When you change out or add something new to the system, that location is most likely to have now developed a leak(s).”

  • System Leaks

Vacuum leaks are, in general, one of the most common issues that arise in a pump or a vacuum system. Leaks in the system hinder the vacuum from maintaining its optimal pressure. It occurs most often when the airflow across the system exceeds the capacity of the pumps to remove. First, try pumping down the system close all of the valves, and watch for the loss of pressure over time. Either compare the leak-up rate to previous tests when no leaks existed. Additionally, a very simple calculation can also be performed. (Q= Delta P x V / Delta T)


Q = Air flow into the chamber under vacuum

Delta P = The change in vacuum pressure (Start / Stop)

V = The approximate free internal volume of the chamber

Delta T = The change of time (Start / Stop)

 An HLD helium leak detector or sometimes an RGA (residual gas analyzer) is very helpful for detecting and pinpointing small to medium-sized leaks.

  • Traps on the ForelineEdwards

When properly installed, foreline traps can prevent oil from recirculating back into the pump, facilitating clean oil. Soiled foreline traps may reduce the vacuum pump's pressure and efficiency, so keeping them clean is essential. There are many different types of inline traps, mostly to keep contaminants from getting into the vacuum pump.

  • Oil

Oil checks are an integral part of routine maintenance. Another good practice is to either place vacuum thermocouple on the pump inlet daily, or if the pump is part of a vacuum system, first verify that the roughing valve is closed, so you can get an accurate indication. Incorrect oil quantity, quality, type, or contamination might prevent the pump from achieving its total base-rated vacuum pressure. So, you should also periodically (daily is suggested!) check the oil to ensure it's clean and full and change the oil if you notice that the oil is changing color from its typical amber color. If the oil gets light brown to whitish, this is an indication of excessive water in the pump oil.  Contrary to this, if the oil becomes dark brown or black, immediately shut the pump down, and drain the oil. Then add a charge of fresh new oil, restart the pump, and watch for any continuing discoloration, you may need to drain and fill; the pump sometimes numerous times, until the oil remains its normal amber color- Additionally, if you can see particulates in the oil, also change the oil ASAP!

Changing the oil in the pump and ensuring it runs smoothly is essential, so check it often. This procedure is crucial if you discover that you have been operating your vacuum pump with the incorrect oil. Making sure you use the correct oil is essential. Here at A-Vac, we utilize Pro-Torr 19, a special type of oil recommended for all rotary vane pumps. 

  • Clogged Inlet

Some users install a protective screen at the vacuum pump's intake to keep unwanted debris out. As the screen becomes clogged with dirt and debris, the vacuum strength decreases. If you can’t physically clean the screen by hand, you will need to get a new replacement screen to repair this.

  • Open Gas Ballasts Valves

Opening the gas ballast valves helps eliminate water vapor. A measured amount of ambient air is allowed into the pump to purge the water vapor out of the pump exhaust. Only open the gas ballast valves as needed as a temporary “fix” when necessary. If you put a vacuum thermocouple gauge tube on the pump inlet, when you open the gas ballast, you will notice a loss of vacuum pressure, because you are purging the pump with ambient air. THIS IS NORMAL! And when you again close the gas ballast, you will see the vacuum pressure return closely to the vacuum pressure you observed, before opening the gas ballast. Don’t leave the gas ballast open longer than 5-10 minutes maximum, because the pump will start to get hot to the touch because it is having to work harder because of the temporary air purge it is trying to fight against.

Our Vacuum Pump Services Cover All Your Needs

A pump may not function to its maximum capacity for multiple other reasons. You should call an expert if you're having trouble figuring out what's causing the pumps' higher-than-normal vacuum levels. Our specialists will also advise you on trustworthy procedures and materials to guarantee that your vacuum pump functions at peak performance.

Our factory-trained technicians offer top-notch services to keep your vacuum pump in optimum condition. If you notice issues with your vacuum pump, don’t let the problem become a major issue. Contact Vacuum Pump Repair USA as soon as you notice your vacuum pump acting out of the ordinary. (1-800-938-1300, or our website is: www.avac.com)

Vacuum Pump Repair