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Pelican Technical Article:

Vacuum Pump Testing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$500

Talent:

****

Tools:

Vacuum gauge, hoses

Applicable Models:

R56 MINI Cooper Hatchback (2007-13)
R56 MINI Cooper JCW Hatchback (2009-13)
R56 MINI Cooper S Hatchback (2007-13)

Parts Required:

Vacuum pump

Hot Tip:

Work with a cool engine

Performance Gain:

Restored engine vacuum and brake performance

Complementary Modification:

Replace engine oil

The turbocharged engines used in MINI R56 vehicles are equipped with a vacuum pump to assist in creating engine vacuum for the engine accessories and brake booster. The vacuum pump is mounted to the left side of the cylinder head and is camshaft driven. The vacuum pump delivers a consistent 25" hg to the brake booster and accessory solenoids.

During operation the vacuum pump will make a knocking or tapping sound, this is normal. When the new engines equipped with vacuum pumps were introduced, the noise emitted was thought to be a problem pump, this however is not the case. Signs of a faulty pump are; low brake booster vacuum, hard brake pedal, brake fade during application when stopped. The brake booster hose nipple on the pump can also show signs of a problem. Look for melted or overheated plastic.

In this article, I'll go over the steps involved with testing the vacuum pump on turbocharged MINI R56 engines. Be sure to work safely, performing tests with the engine warm and when idling. Stay clear of hot surfaces and moving parts.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

The vacuum pump is mounted to the left side of the cylinder head and is camshaft driven (red arrow).
Figure 1

The vacuum pump is mounted to the left side of the cylinder head and is camshaft driven (red arrow).

With the engine running, test vacuum output at the pump outlet to confirm the check-valve in the brake booster vacuum hose is not the issue.
Figure 2

With the engine running, test vacuum output at the pump outlet to confirm the check-valve in the brake booster vacuum hose is not the issue. Vacuum at the vacuum pump outlet should be about 25" hg. To check output vacuum, install a vacuum gauge T test adapter into the output line as shown. Red arrow to brake booster. Yellow arrow to vacuum pump. Blue arrow to test gauge.

Idle engine until it reaches operating temperature.
Figure 3

Idle engine until it reaches operating temperature. The vacuum pump should make a minimum of 25" hg (red arrow). If less than 25" the pump is considered faulty.

With the engine idling, press the brake pedal, vacuum on the gauge will drop about 5 hg (red arrow) each time the pedal is pressed.
Figure 4

With the engine idling, press the brake pedal, vacuum on the gauge will drop about 5" hg (red arrow) each time the pedal is pressed. If pump drops 10" hg or more when brake pedal is pressed once, the pump is faulty. A bouncing needle on the test gauge is normal, this happens as a result of the pump building vacuum.

To test the vacuum pump check valve: Remove the brake booster vacuum line from the vacuum pump, press the brake booster line release tab (red arrow) and pull the vacuum line straight off the pump (inset).
Figure 5

To test the vacuum pump check valve: Remove the brake booster vacuum line from the vacuum pump, press the brake booster line release tab (red arrow) and pull the vacuum line straight off the pump (inset). Attach a hand pump to the check valve. Pump up to 25" hg. Check valve should hold vacuum until hand pump vacuum pressure is removed. If the pump check valve seal fails, oil can travel up the brake booster vacuum line. If the oil then gets past the check valve in the vacuum line and contaminates the brake booster diaphragm, the brake pedal may begin to feel soft or spongy and may fade while waiting at a stop light. If brake booster symptoms appear, check the vacuum booster line for oil. The oil eventually ruins the rubber diaphragm of the brake booster.

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