I have to pump the brakes at times to stop my 81 300 TD. There are no leaks, vacuum is good, and maybe the cause is ?????? TIA

bill

Probably a bad master cylinder.

With the car off, apply very light pressure to the brake pedal and see if it slowly sinks to the floor. Try again with heavy pressure. Bad master cylinder will usually sink faster at low pressure (but not always).

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Gone to the dark side

- Jeff

yeah ive been down this road before, sounds like ur master cylinder as stated above, probly not ur vacum booster due to the fact that ur holding good vacum
however, try to test the vacum while getting some one to pump the brakes

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82' 300SD

Could just need to be bleed 'em. That'd be the first repair to make if you haven't noticed any leaks from any of the wheel cylinders or master.

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

Just finish doing your suggestion.....at low or high pressure the pedal does not go to the floor... there is pressure on the pedal and slowing the pedal moves slowly towards the floor and stops at low and high pressure ... therefore, there is a small leak in the MC.... thanks

bill

I have seen before where mc's fail and don't leak externally, as they failed in between the two internal pistons, or the check valves to the reservoir began leaking back.

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale

Good oportunity to install all new brake fuid at the same time. Makes a difference.

another way is like stopping at stop light, your foot shall move forward slowly then is a sign of MC leaking. reason with car in drive you need extra brake power to hold her still, should Mc leaking then pedal will bleed internally.
Should wheel cyl leaks, u can watch for oil stain when park over night on wheel. Plus brake fluid wont last very long, is no more than a little tea cup of brake juice anyways.

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