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Maintaining a brake vacuum pump (brake booster)

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  • OVERALL DIFFICULTY INDEX: 3/10
  • IF YOU HAVE NO TOOLS YOU SPEND $ 30 TO GET THEM FOR THIS JOB
  • IF YOU HAVE NO EXPERIENCE YOU SPEND 3 HOURS TO CARRY OUT THIS JOB
  • RISK OF BURNS, SEE BELOW
BEFORE YOU START
  • Always work on a cold engine to avoid burns.
  • The below works are valid for attempting a repair against a loss of servo assistance when moving a vehicle slowly and shifting to neutral in particular. Do not consider this intervention for a permanent loss of the brake servo assistance or if the brake pedal becomes stiff when driving!
  • The vacuum pump in this case is mounted on the cylinder head and driven by the camshaft. Those works have been carried out on a Peugeot 5008 1.6 THP 156HP (EP6 engine) but remain similar for other non electric vacuum pumps.
DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.

Brake vacuum pump removal

Remove whatever air hoses hiding the pump.
Disconnect the servo brake vacuum hose from the pump.
Unscrew the pump holding bolts (left and middle) and take it out. You might need to use a large slotted screwdriver as a lever (right).
The pump is driven by the exhaust camshaft (left).
Remove the turbocharging regulation vacuum hose in case you did not do so before (right).

Brake vacuum pump dismantling and cleaning

Put the pump in a clean tray and remove the cover screws (left).
Remove the vacuum outlets (middle).
The pump is simple in construction and made of robust material and components. Its weak point however is explained further below. Note well how it is lubricated by the engine oil itself which with time becomes thick and sticky (right).
Now here comes the problem: both vacuum connections to the servo and turbo regulation circuit contain a basic check valve made of a rubber disc and a spring. The disc can stick in place or the opening can get obstructed by the thickened and aged oil.
The fix consists of freeing the check valves by cleaning them.
NOTE: the vacuum pump connector is available as a spare part from our partners' store, in case you'd like to replace it:
  • Put the connectors in a glass jar filled with a little clean engine oil and spray them well with a carb cleaner (left).
  • Leave them for not less than 30 minutes soaking into the mix of carb cleaner and oil. Do not immerse them in the carb cleaner alone.
  • Use compressed air to dry them up (middle).
  • You should be able to see now the color of each component.
  • Gently blow through them with your mouth in the same vacuum direction (outside to inside) and make sure air passes through.
Clean well all other parts to get the rid of the aged oil:

Refitting

  • Replace the connectors' seals with new ones. You will find these at a specialized industrial rubber material shop or hardware shops.
  • Use exclusively high temperature EPDM or Silicone O-ring seals for the connectors.
  • Replace the pump to cylinder head seal, available as a spare.
  • Pour some 50 ml of engine oil into the pump and one drop into each connector prior to closing the cover.
  • Use RTV silicone gasket maker applied directly on the pump cover seal if you don't find a match for this one.
  • This is the only place where the RTV gasket maker can be used.
Now clean well the servo vacuum hose connector with your carb cleaner and use some grease on the pump and servo connectors prior to reinstalling it.
Test the vehicle over a period of days.
Replace the vacuum pump with a new one if this fix doesn't eliminate the above described symptom.
Note: testing the pump with a vacuum gauge won't necessarily return a clear result since such symptom is of intermittent and unexpected nature.
You may buy your brake vacuum pump here, make sure of the compatibility with your vehicle:

See also our complete EP6 engine repair manual:

And more DIY tips for all types of cars: