Pedal goes to floor

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nothingbutdarts

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OK, vehicle is an 80 Crew Cab, a few years ago I put on a rebuilt master cylinder. Well the rear wheel cylinder are leaking so, I have replaced them, have not yet added any brake fluid to the smaller front section of the divided master cylinder (the side that feeds the rear wheel cylinders) without the fluid added the brake pedal goes all the way to the floor, even though there is no fluid in the smaller front section the bigger rear reservoir is almost full (it feeds the front calipers) question is, should the pedal not bee off the floor somewhat because the rear side (front disc. side) is still working?

Thank You!
 
If properly working, there should be some pedal pressure before the floor as you are thinking. One of 3 things comes to mind:
1) The MC is now faulty and there is a leak between the front a rear sections
2) The front caliper pistons are pushed back a bit for whatever reason and won't pump up properly now.
3) The MC has all sorts of air in it now. If you left the rear lines open for a long time, and then pushed the pedal then that is the most likely thing going on. The MC may need to be completely 'bench' bled again (which can be done on the car). You will only know if you hook up the rears and try to bleed them; if they don't bleed right, then bleed the MC.

I would never push on the pedal with part of the system open, BTW; that presents the possibility of getting air in the MC and needing the re-bleed the MC. I also plug the open lines, keep fluid in both MC reservoirs, and work fast for the same reason: keep air out of the MC.
 
nm9stheham said:
If properly working, there should be some pedal pressure before the floor as you are thinking. One of 3 things comes to mind:
1) The MC is now faulty and there is a leak between the front a rear sections
2) The front caliper pistons are pushed back a bit for whatever reason and won't pump up properly now.
3) The MC has all sorts of air in it now. If you left the rear lines open for a long time, and then pushed the pedal then that is the most likely thing going on. The MC may need to be completely 'bench' bled again (which can be done on the car). You will only know if you hook up the rears and try to bleed them; if they don't bleed right, then bleed the MC.

I would never push on the pedal with part of the system open, BTW; that presents the possibility of getting air in the MC and needing the re-bleed the MC. I also plug the open lines, keep fluid in both MC reservoirs, and work fast for the same reason: keep air out of the MC.
Click to expand...


The biggest reason I left the lines open was to try and totally drain out the old fluid from the lines because it's like 30some odd years old. The old wheel cylinders were real cruddy inside.

Thanks for the info. I'll check it out and rebleed the master if I have to. I'm not so sure the front calipers aren't frozen as it's has been sitting for so long. There are no rebuild kits available for the front calipers any more for the Dana 60 front axle, so I haven't pulled them apart.
 
why would you pump the brakes with no fluid in the mc?wow,starting all over now
 
nothingbutdarts said:
The biggest reason I left the lines open was to try and totally drain out the old fluid from the lines because it's like 30some odd years old. The old wheel cylinders were real cruddy inside.

Thanks for the info. I'll check it out and rebleed the master if I have to. I'm not so sure the front calipers aren't frozen as it's has been sitting for so long. There are no rebuild kits available for the front calipers any more for the Dana 60 front axle, so I haven't pulled them apart.
Click to expand...


if you have a 1980 dodge nobody bothers with backyard rebuilding anymore, there under $60 each for calipers and a normally stocked item

if you drained the master cylinder and pumped the pedal you will have fun now, the master will need to be "bench bled" (done on vehicle) then the proportioning valve will have to be checked to make sure its still centered
 
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