Building a Vacuum Bleeder

A suspension vacuum bleeder uses alternating vacuum and pressure to bleed a damper. It's much easier than hand bleeding, does a better job, and is a less mess.

Bill of Material

A bleed adapter specific to the damper will be required to connect the vacuum bleeder to the damper. ANSO (https://anso-suspension.com) makes good bleed adapters at a reasonable price, and the list below reflects using ANSO adapters. If different bleed adapters are used, the "3/8" FNPT V-Style coupler" would need to changed to work with those adapters.

• 1/4" NPT 50 PSI pressure relief valve - $9 -  https://a.co/d/7lOzOpp
• 3/8" OD 1/4" ID polyurethane (PU) tubing - $9 - https://a.co/d/7cUTqff
• 1/2" NPT to 1/4" barb 90* fittings - $10 - https://a.co/d/fgpZFRI
• 3/8" spring hose clamp - $6 - https://a.co/d/gdm5f48
• 3/8" FNPT V-Style coupler - $9 - https://a.co/d/8DQBxJ5
• 1/4" NPT pressure gauge - $13 - https://a.co/d/f1TbRqJ
• 1/4HP 3.5 CFM vacuum pump - $55 - https://a.co/d/2L3zF0F
• Hydronix HF2-10CLWH12 filter housing - $23 - https://a.co/d/dYMTLSv
• 3/8" NPT 3/8" tubing push to connect fittings - $9 - https://a.co/d/auJHnwp
• 1/2" NPT mini ball valves - $13 - https://a.co/d/72oPZEk
• 1/4" FNPT air hose quick connect adapter - $4 - https://a.co/d/aGIQmXG
• 1/4'' NPT 1/4" barb fittings - $5 - https://a.co/d/cOngmrj

TOTAL - $165

Assembly

NOTE: Whenever installing a fitting the threads should be wrapped with at least three layers of Teflon tape. Be sure to orient the wrap so that tightening it doesn’t try to un-wrap it. 

Vacuum Pump

• Fill the vacuum pump’s sump with suspension fluid, roughly the same viscosity as you’ll be using.
• Remove the inlet fitting and replace it with a 1/4” NPT barbed fitting.

V-Style Coupling

• Install a 3/8” NPT push-to-connect fitting.

Quick Connect Coupling

• Install a 1/4” NPT barbed fitting.

1/2” Ball Valves

• Install the 1/2” NPT barb 90* fittings so they point away from the valve handle.

3/8” Push-to-Connect Fitting

• In one of the fitting, drill out the bottom of the fitting so a tube can extend all the way through the fitting.
• Meticulously clean any metal swarf out of the fitting.

Filter Housing

• Drill a 19/32” hole in the top of the lid and and thread in the drilled out 3/8” push-to-connect fitting. Teflon tape is not needed on the thread. The fitting will tap itself into the plastic of the lid. Keep threading it in until the bottom is just proud of the inside of the lid.
• Drill a 15/32” hole in the top of the lid, then thread in the pressure gauge. Teflon tape is not needed on the thread. The gauge will tap itself into the plastic of the lid. Keep threading it in until the bottom is just proud of the inside of the lid.
• Drill a 15/32” hole in the side of the lid and thread in the 1/4” NPT pressure relief valve.  Teflon tape is not needed on the thread. The valve will tap itself into the plastic of the lid. Keep threading it in until the bottom is just proud of the inside of the lid.
• Clean out any plastic shavings from the lid.
• Install the two two ball valves into the two threaded holes in the lid. The valve handle should face upward, and the barb fitting should face downward.

Putting it all Together

• Insert the polyurethane (PU) tubing through the push-to-connect fitting in the lid and feed it down until it sits about 1/4"-1/2” above the bottom of the reservoir. Install a zip-tie or clip to prevent the push-to-connect release collet from being depressed.
• Cut the PU tube to length. It needs to be long enough to go from the vacuum bleeder to the damper with some slack in the tube. However, the tube should be kept as short as practical to aid in bleeding.
• Connect the V-style coupling to the end of the PU tube. Install a zip-tie or clip to prevent the push-to-connect release collet from being depressed.
• Cut a length of PU tube to connect the reservoir to the vacuum pump. Put two spring clamps on the tube, warm up the two ends with a hair dryer or heat gun, connect them to the barb on the vacuum pump the barb on one of the ball valves on the reservoir; this is now the vacuum valve. Put the spring clamps in place.
• Cut a length of PU tube to connect the reservoir to the air compressor. Put two spring clamps on the tube, warm up the two ends with a hair dryer or heat gun, connect them to the barb on the quick connect coupling and the barb on the other ball valve; this is now the compressed air valve. Put the spring clamps in place.

Testing

• Test the reservoir to make sure it holds vacuum. Close the compressed air valve, open the vacuum valve, and run the vacuum pump until the pressure gauge registers 30 in. of Hg vacuum, then close the vacuum valve and turn off the pump (air can bleed through the vacuum pump when it’s not running so close the vacuum valve before turning off the pump). The reservoir should easily hold the vacuum for several minutes, if not hours. If it doesn’t, there’s a leak which needs to be found.
• Test the reservoir to make sure it holds pressure. Pressurize the reservoir to 45-50 PSI and close the compressed air valve. Set the air compressor’s regulator to 45-50 PSI, DO NOT pressurize the reservoir with higher pressure air and try to stop it at 45-50 PSI using the pressure gauge. Again observe the pressure gauge for any changes in pressure. If the pressure drops over the next several minutes, there’s a leak which needs to be found.

If the system passed both the vacuum and pressure tests, install it in its final position or install it in its stand/frame.