brake problems

[brentleedragon]

Ok so in my 79 F-150 with power brakes, i will be driving along and when I come to a stop the brakes at first work fine and the truck begins to stop but the harder I press on the pedal (sometimes I dont even have to press that hard on the pedal) they will begin to fade until the pedal is more or less to the floor. The pedal however does come back after this and if I pump the pedal the brakes somewhat return.I found no leaks on any caliper/drum/ or anything like that, the MC is not leaking and is still maintaining proper fluid levels. Is this my brake booster? and if so what applications fit this? because I can get a working booster/mc out of a 79 f150 supercab, or a 78 f-250 reg cab ? Is any brake booster/mc going to work on the truck? or am I going to have to get the "exact" one for my truck? I no nothing about this :-D

 

[blacksnapon]

Ok so in my 79 F-150 with power brakes, i will be driving along and when I come to a stop the brakes at first work fine and the truck begins to stop but the harder I press on the pedal (sometimes I dont even have to press that hard on the pedal) they will begin to fade until the pedal is more or less to the floor. The pedal however does come back after this and if I pump the pedal the brakes somewhat return.I found no leaks on any caliper/drum/ or anything like that, the MC is not leaking and is still maintaining proper fluid levels. Is this my brake booster? and if so what applications fit this? because I can get a working booster/mc out of a 79 f150 supercab, or a 78 f-250 reg cab ? Is any brake booster/mc going to work on the truck? or am I going to have to get the "exact" one for my truck? I no nothing about this :-D

Thats usually a sign of air in the lines or a leak. Theres a possibility of the MC leaking into the booster as well.

 

[radialarm]

Sounds like a bad MC to me (leaking past the plunger). If the pedal goes to the floor. A bad booster wouldn't do that. The booster assists your brakeing.

 

[SuperCab]

Yeah, sounds like mc to me. But just for the record, any booster should work - that sc one would, iirc, be fine.

 

[Mil1ion]

Master cylinder needs replacing.

What happens is the fluid compresses then flows back into the reservoir causing the pedal to drop.

Get a replacement with a stainless steel bore.

 

[brentleedragon]

is there a way to see if the power booster is out? i mean what can I do to test this? becuase I dont want to take it apart if I dont have to

 

[Mil1ion]

 

[Mil1ion]

Note the difference in mounting

This booster is for a 1979 with build number DJ0001 and higher.

This booster is for 1977-1979 with Build number before DJ0000.

 

[Mil1ion]

Brent if you need eventually need the top one.... 1979 After DJ0001

The one shown is for sale and is working.

 

[brentleedragon]

Nothing is leaking anywhere, I checked it all, and it is all fine. I havent replaced the MC yet. But I dont have a vacuum gauge my last two got ran over by my sister on her ATV aha, but I will get a friend to help me out with the gauge and look at the build code I do not remember what it is lol.

 

[brentleedragon]

I probably do, but I need it asap like tomorrow as this is my daily driver ahah

 

[Skandocious]

Nothing is leaking anywhere, I checked it all, and it is all fine. I havent replaced the MC yet. But I dont have a vacuum gauge my last two got ran over by my sister on her ATV aha, but I will get a friend to help me out with the gauge and look at the build code I do not remember what it is lol.

Brent it doesn't necessarily need to show leaking anywhere. Your master cylinder could be leaking internally.

 

[brentleedragon]

yeah im figuring my master cylinder is bad. i meant all of the other connections not the mc

 

[Mil1ion]

Brent, I stated the BB is probably fine ,your problem is the piston seal in the Master Cylinder that has become faulty.. a common occurence.

 

[COUNTRYBOY77]

JUST FOR THE HECK OF IT BLEED THE BRAKES IT WONT HURT YOU KNOW

 

[Mil1ion]

After he changes the M/C.

People need to know that brake fluid absorbs water and eventually it needs evacuating from the system.

It's best having new from an MC replacement.

They can be gravity bled as well