I am bleeding the breaks on my truck to try to eliminate a spongy pedal the and I also needed to replace the wheel cylinders in the rear, but my question is that when the break line is disconnected it drains all of the fluid from the system right down to emptying the master cylinder so I was wondering if maybe my master cylinder is bad and therefore causing my spongy pedal.
it could be the master cylinder. if you pump the pedal very fast do you get pedal for a second then lose it? what vehicle are you exactly bleeding./
A bit more info needed. Single or dual M/C? drums or disk drums? If M/C is above the end of the line it is possiable for them to drain by gravity.
A disconnected line will drain the master. Also you need to replace the rear wheel cylinders if their bad before the pedal will feel right
I am only replacing the rear cylinders because the bleeders are seized I don't think they are bad thou, but I was concerned about a bad master cylinder when I saw it draining like that it made me think that the seals might be bad in the master cylinder.
yup. pump the breaks a bunch. if you get a still pedal then it bleeds off to the floor............... bad master cyl!
Draining like that does not mean the M/c is bad. Get the rear W/C issue fixed and then if you still have a spongy pedal start looking at the M/C . Those damm dual cylinders tend to fail fairly often IMHO! In 9 years and 180K I've replaced 3 on my 94 Ranger.
HA! You need to come up here to the land of rust I couldn't get them lose even after letting them sit for a few days with penetrating oil and a pipe wrench or the vise grips that I used as a last resort so for the $13 it cost for a new wheel cylinder I just got them instead.
If you let all the fluid drain out, you may need to bench bleed the M/cyl again to get it back to snuff just like starting with a new dry one in the box. If air was able to enter the piston, you'll have to start over again. I never liked gravity bleeding for this reason. If there was fluid still in the reservoir then you are probably ok.
if you pushed the pedal all the way to the floor it is very likely that you floded the seals over.Your spongy pedal is probably form air trapped in the system. Go to autojoke and buy a pressure bleeder. You will save way more in brake fluid than you spend on that tool. Bleeding stuff sucks.
Well I just finished bleeding the brakes and installing the wheel cylinders but I still have a spongy pedal, I tried pumping up the breaks a bunch to test the master cylinder but it still doesn't have much pressure. I started up the truck to get some pressure in the booster but with the truck running the pedal slowly goes to the floor.
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