Master cylinder won’t bleed or build pressure

[Bubs]

Hello got a 1981 xs400. Trying to rebuild the front brake master cylinder. Got the kit took apart the master and the seals were destroyed all cracked and in pieces. So I don’t know where the new seals are suppose to go. Can someone tell me if this is the correct way everything is suppose to go in. When installed as shown it won’t bleed or build any pressure when depressing plunger with a screwdriver.

For reference It’s off the bike and I have the caliper hanging down off the table and the master on the table I’ve been filling the hose with fluid before I put the plunger in also.

 

[JPaganel]

That looks about right...

Maybe worth going back to basics.

Is the bore clean and smooth with no scratches? Are you sure you got the right seals? Did you make sure to clear out the small return hole?

 

[tstidham]

I had similar issues when I rebuilt mine last year. I bled mine while still mounted on the bike but I found tapping the body with a screwdriver handle caused bubbles to percolate out of the openings in the bottom of the reservoir. It took a while of slowly pumping and tapping to get fluid to start moving and reach the caliper.

 

[Bubs]

the kit came with the bike the plunger and spring is for sure correct. I didn’t have seals to base off of so unsure of those but they fit tight.

 

[Bubs]

That looks about right...

Maybe worth going back to basics.

Is the bore clean and smooth with no scratches? Are you sure you got the right seals? Did you make sure to clear out the small return hole?

The bore looks good return hole is clean it does bubble when pumping. Just doesn’t force fluid past. If I remove the plunger sling and seals I can run fluid through it.

 

[Bubs]

That looks about right...

Maybe worth going back to basics.

Is the bore clean and smooth with no scratches? Are you sure you got the right seals? Did you make sure to clear out the small return hole?

Wait by return you mean the hole under the small plastic flap ? I have not checked that one.

 

[drewpy]

good way is to back bleed using a syringe, pull the fluid down forcing it past the master seals. pump brake too to help move the fluid.
I've had mu callipers suspended above the master cylinder so bubbles rise to the bleed nipple overnight.

 

[kebabs]

Hello got a 1981 xs400. Trying to rebuild the front brake master cylinder. Got the kit took apart the master and the seals were destroyed all cracked and in pieces. So I don’t know where the new seals are suppose to go. Can someone tell me if this is the correct way everything is suppose to go in. When installed as shown it won’t bleed or build any pressure when depressing plunger with a screwdriver.

For reference It’s off the bike and I have the caliper hanging down off the table and the master on the table I’ve been filling the hose with fluid before I put the plunger in also.

if all seals are fine ,no leaks .keep bleeding took me 4 hours but got there.
I also use a piece of pipe with no return valve attached to the bleed nipple.