When I get in and first start the truck the brake pedal goes all the way to the floor.  It still stops the truck and if you remember to pump the brakes the pedal is fine and the truck stops.  The system has been bled, master cylinder was changed about 6 months ago, dealer says it checks out fine


Everything works perfectly with the brakes except that first push


Any thoughts

Sounds like theres a leak somewhere letting air get in, have you checked the rear slave cylinders and front caliper seals?

I had Brake Masters check everything and they came up with nothing

They work perfectly so if there was a leak would it only be that first push of the pedal after it sits for 8 hours or more?

im wondering something here .
 when i did my swap from a 89 rear end to the 95  rear end . i found that up above the rear A fraim was  another  proportion type valve that apeared to be spring loaded . IE there was a spring that came down and attached to the A frame . the 95 did not have this .
  i assume that  this little vale is a safty type of break  that is activated by the spring , if the rear end over exstends .
 i wondering if you have this same system , if the spring was broke or missing if it would alow the  lever to  to move on start up ?
 just a thought

im wondering something here .
 when i did my swap from a 89 rear end to the 95  rear end . i found that up above the rear A fraim was  another  proportion type valve that apeared to be spring loaded . IE there was a spring that came down and attached to the A frame . the 95 did not have this .
  i assume that  this little vale is a safty type of break  that is activated by the spring , if the rear end over exstends .
 i wondering if you have this same system , if the spring was broke or missing if it would alow the  lever to  to move on start up ?
 just a thought

That spring loaded thing is a LSPV (load sensing proportioning valve).  It basically applies more or less rear brake pressure, depending on the load that is being carried.  I do not think that would have any affects on (or cause) the pedal going all the way to the floor after the vehicle has sat for several hours.

 good to know , thanks for the info . thought it just might be a place to look at .
 i do know there is a bleeder nipple on mine so ?

I made them bench bleed the system, master cylinder out of the vehicle and then do each line, and it seems to be okay at this point.  We figure there must have been a bubble of air in the line somewhere