Ok so my 88 Ford f250 started having brake problems the pedal goes to the floor while holding pressure on the pedal there are no leaks at the wheels or lines but the master cylinder is low could it be a bad master cylinder

 

Could be the master cylinder or the booster itself

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If there are no leaks then it is the mc, but it could be leaking into the booster, only way to find out is pull it

 

How much pressure are you applying? Doesn't the ABS system on these make your pedal fade if you push hard? Could it be that malfunctioning?

 

Your brake master cylinder is bypassing ... Replace it and start again with all new fluids ...

 

Thank u everyone

 

No problem ....

 

Ok kind of an update. with the truck shut off and no vacuum in the booster the pedal is hard and it stays hard without sinking to the floor. should I just replace both booster and master cylinder and be done with it?

 

I would, extra insurance and piece of mind

 

Ok thanks for the help

 

Yes , Relapce it ... even a worn out master will be hard to depress W/O assist ... when you need it its good to have ... and there cheep ... also every 2 years ... dump and flush your brake system .... keeps the moisture content low and the fresh fluid has a higher pressure holding ability ...
Just like Engine oil ... it needs to be fresh in order to attain the right protective layer and cushion against galling and such ..