struggling w/bleeding brakes, o/s front caliper won't bleed

[xpress]

got a problem with bleeding the van please help it's driving me mad. the front bleed screws seem seized and feel like they're gonna round off even with a 7mm ring spanner on them tightly, also they seem to be in a stupid place they're right near the hoses, why not put them the other way around or further away from the hose?

so anyway i bled the backs only one release nipple, they all bled ok with flow got a good amount out of each, about 200ml in total,

then round to the front. got flow from the drain screw on the n/s front started until it started to splutter.

discovered the eezibleed wasn't filling up the filler properly, arg! shouldn't the eezibleed keep this topped up! (the tyre may have gone down in pressure to about 10 psi, so i remember topping it up to about 17psi and carrying on), also not sure to trust this eezibleed is it normal to see a little bit of air escaping from one of the little tubes going into the top of the eezibleed bottle? the flow through the pipe to the master cylinder seemed fine albeit a bit bubbly? i would have thought it should have been clear otherwise is that pushing air in or does it not matter?

anyway, took the m/s cap off and topped it up. went back to trying to bleed the o/s front caliper, opened the drain screw on the o/s front and could get nothing out. (same story, the bleed nipple seems like it's going to round off with a 7mm ring spanner on it, so tried to get fluid out of the drain nipple).

but no brake fluid. even with the cap back on the master cylinder and by pressing the pedal to the floor, opening the drain nipple, then closing it, then bringing the pedal up and repeating loads of times. van's been in a garage and bled before on the fronts via the drain screws not the bleed nipples, so i can't understand why i am not getting flow through the drain screw on the o/s front, you would think that the pedal pressure would be strong enough if there was any crud in the way.

i'm most concerned with not being able to get any fluid out of the front o/s drain screw even when pumping the pedal, the master cylinder filler is full. underneath, i can hear the brake fluid moving as the pedal goes up and down.

any advice? if you're local and you are into a challenge i would be very grateful if you want to take a look, i am supposed to move the van today

[Ian Hulley]

any advice?

Have it done by a professional or someone that knows what they are doing.

[xpress]

are you trying to say that i don't know what i am doing?

are trying to troll me? i've seen your caustic replies in other threads, can you do me a favour and do something else because I won't be listening.

thanks for your advice specifically not useful, and not designed to help "me", do something for myself.

[Ian Hulley]

You wanted advice, I gave it. Good, safe advice.

[AdrianC]

even with the cap back on the master cylinder and by pressing the pedal to the floor, opening the drain nipple, then closing it, then bringing the pedal up and repeating loads of times.

The usual manual bleed procedure is...

Pedal up.
Crack nipple open.
Slowly pedal down.
Nip nipple closed.
Pedal up.

Difference is that you're only opening the nipple with the pedal already down, whereas it's the travel in the master which forces the fluid (and air) out.

If the bleed nipple's seized and rounded, sort that properly first. If you're trying to bleed air out from a "drain nipple", presumably at the bottom of the caliper (I've never seen such a thing on any caliper, but I've not looked closely at the T25's yet), then it's not going to get air out anyway - air rises, remember?

[xpress]

what you're saying is right. i reverted to the manual procedure as you describe but was puzzled at not getting any fluid at all even when taking this drain screw right out, there's fluid from all the other drain screws on the other wheels, and the m/s cap is full. maybe i should leave it for a bit to let gravity do its job and then come back to it. i did this on another car came back the next day and it bled straight away. i know it's sometimes a bit hard to get all the air out. the local garage bled the fronts from the drain screws when the bleed screws were stuck and the pedal was fine. on the o/s front drain screw, i can see traces of brake fluid on the pointed end of it that goes into the caliper. might try and blow in it with a straw to see if there's a blockage.

[Oldiebut goodie]

Have you checked that that brake itself is working to start with? It could be totally seized up and not worth flogging a dead horse. Or require a total strip down and refurbish/replacement.

[xpress]

thanks for the suggestion. in answer, both front calipers have been off, cleaned up, resealed and booted and tested with air, both pistons come out and can be pushed in without too much effort. going to grab my laser sump suction pump thing and see if i can suck anything out of this drain hole and will try and blow through with a straw. will see if there's a blockage. there wasn't a blockage before i put the caliper on the vehicle. it might be that there's an airlock or something in the master cylinder? however fluid is coming out the front n/s caliper, so can't work out why not getting any fluid from the o/s front. will keep on with it and will keep checking in. cheers

[silverbullet]

Problems with the offside front may be that the hose has failed and as you pressurise with the pedal, the hose is collapsing internally, so it won't bleed. It does happen sometimes.
Either that or the bleed nipple is rusted up down the drilling, so can't pass fluid when cracked.
P.S. I have never heard of or seen "drain" nipples on brake calipers, ever.

[xpress]

cheers for that will take a look at the hose. also going to undo the union between the caliper pipe and the hose and see if fluid comes out, maybe an airlock in there.

drain nipple = drain screw. there are two screws on the fixed twin piston calipers, a bleed nipple and a drain screw. both appear to be 7mm.

just checking, if the master cylinder is not working right, the pedal would be on the floor wouldn't it? another symptom would be bubbles in the filler hole? at this stage if i open up the drain hole i should see a more pronounced squirt of fluid if i pump the pedal, the drain hole and bleed hole inside the calipers lead to each 7mm drain screw/bleed nipple on the outer casing.

[kevtherev]

pumping the pedal will draw air into the lines
if you bled the others then the master cyl is working
air lock is impossible in a hydraulic brake system
pedal always returns to the top as it's sprung
I think they are both bleed screws on the calliper

when you removed the nipple was it in tact with a pointed end?

[xpress]

Hi rev, thanks for stopping by. Yes, the offending drain screw is pointed and fluid was on the end of it. I have a sump sucker will try and suck the hole with a straw and will try and pump about six times and then open that part of the circuit again.

I have some more bleed nipples on order, will clip the hoses with some clothes pegs and fit those, will probably need some heat if I don't want them to snap and a visit to the machine shop.

What size unions go into the hose? I need to order some, I have some 3/16 pipe roll of kunifer when I did the pipes on another car. If I replace the hose I will need to replace the pipe, does the front o/s pipe go to the master cylinder?

I have some rubber grommets and grease for when this is all done

.

[xpress]

Ps; anyone with a link or a jpeg of the moprod sizes for the complete brake lines? Might end up doing the lot.