Hard brake pedal

[87F-250HD]

So my brakes on my ‘87 6.9 were fine until this morning; now suddenly the brake pedal is hard and riding high and it’s very difficult to stop the truck. Any idea what this could be or how to fix it?

 

[Kdo58]

Brake booster, you should probably replace brake master cylinder and booster together.

 

[Rdnck84_03]

Check to make sure the vacuum pump is working. If the pump is making vacuum and there are no leaks then I would look at the booster.

James

 

[87F-250HD]

Thank you! What’s the best way to check the vacuum?

 

[Greenie]

Vacuum gauges were pretty common in garages engines had carburetors they'll give you an exact reading. Napa sells them for about $30. Under 17" is bad, 19" or more is good.

 

[IDIBRONCO]

Thank you! What’s the best way to check the vacuum?

The easiest way is to pull off a vacuum line while the engine's running and then put a finger over the end that is still attached to the vacuum system. You'll feel a pull on your finger if the vacuum pump is working. It's also cheap and easy. A vacuum gauge is something that I also recommend in everyone's truck to keep an eye on the vacuum pump.

 

[Cant Write]

Brake booster, you should probably replace brake master cylinder and booster together.

Why should they be replaced together? I just never heard this, so just wondering the logic. Thanks!!

 

[Rdnck84_03]

Why should they be replaced together? I just never heard this, so just wondering the logic. Thanks!!

When I replaced the booster on my 83, I was told that I should replace the master at the same time because they wouldn't warranty the booster if the master cylinder seal leaked fluid into it.

James

 

[Greenie]

I replaced the master cylinder 3 years ago the booster was original (1993) and is still working OK

 

[Kdo58]

The brake booster normally go bad because the brake cylinder leaked into the booster.