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77 620 brake booster


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The test for operation is to depress the brake pedal several times to empty any remaining vacuum. Then depress the brake and hold down. Now start the engine. What should happen is the pedal should drop slightly lower as the intake vacuum rises. If it does, it's working.

 

Check that the vacuum line to the booster is not cracked and the hoses are tight.

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1 minute ago, datzenmike said:

The test for operation is to depress the brake pedal several times to empty any remaining vacuum. Then depress the brake and hold down. Now start the engine. What should happen is the pedal should drop slightly lower as the intake vacuum rises. If it does, it's working.

 

Check that the vacuum line to the booster is not cracked and the hoses are tight.

Ok thanks , cause when I drive the past couple days I have to pump the brake three or 4 times to stop , the pedal will go all the way down at first then after it will give some pressure 

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That fast could be low brake fluid in the master cylinder or air in the lines. If this happened over weeks it would likely be the brake drums need adjusting for shoe wear.

 

I would inspect all lines and wheel cylinders for leaks that might cause the fluid level to drop.

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8 minutes ago, datzenmike said:

That fast could be low brake fluid in the master cylinder or air in the lines. If this happened over weeks it would likely be the brake drums need adjusting for shoe wear.

 

I would inspect all lines and wheel cylinders for leaks that might cause the fluid level to drop.

I check my fluids and it still stayed full , and I can another brake fluid change 

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Have you done any work on the brakes lately?????

 

 

 

If the brake system is working properly loss of the booster just increases the effort to get stopped. It feels like there's a brick under the pedal and extremely had to push down on.

 

If you have to pump the pedal several times then either there is air in the lines or the shoes need to be adjusted. When the shoes wear down (even slightly) they have to travel farther and farther to contact the drums. This will use up lots of pedal travel.

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6 minutes ago, datzenmike said:

Have you done any work on the brakes lately?????

 

 

 

If the brake system is working properly loss of the booster just increases the effort to get stopped. It feels like there's a brick under the pedal and extremely had to push down on.

 

If you have to pump the pedal several times then either there is air in the lines or the shoes need to be adjusted. When the shoes wear down (even slightly) they have to travel farther and farther to contact the drums. This will use up lots of pedal travel.

I did change the back brakes two months ago and everything was fine , this just started happening 

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  • 8 months later...

Jumping in here.  My ‘78 620 kc has similar problems.  The master cylinder is shot so I will be replacing that.  Although the booster may be fine, I want to catch that before the inevitable failure.  Problem is that I am finding it difficult to locate (without unspecified delays).

The part number is 53-5240.   Are there others that can be substituted?  
my rubber brake lines are also looking worse for wear, especially the fronts (disc). Best bets on good quality replacements.?

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