Replaced callipers

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Rorie

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641
Just replaced all 4 callipers on my 90. Bled the brakes and no air coming out them now. Used the 'two person method' where i cracked the nipple on the downstroke and shut before the upstroke.

Several passes with no air bubbles - job done. Or so i thought.

Took the car up the road and need to pump the brakes to get them to work. I assume there must be some air in the system. Perhaps in the callipers themselves?

Any suggestions on how to solve this if i am not getting any air out the nipple?
 
The nipple bleeds the caliper. As said, correct order and keep pumping. Top reservoir up regularly! Don't let master cylinder suck air in.
 
Yep still air in the system somewhere. You
Can narrow it down by clamping each flexi pipe in turn and see if the pedal improves.

I find using a pressure bleeder the easiest way
 
Rorie said:
Just replaced all 4 callipers on my 90. Bled the brakes and no air coming out them now. Used the 'two person method' where i cracked the nipple on the downstroke and shut before the upstroke.

Several passes with no air bubbles - job done. Or so i thought.

Took the car up the road and need to pump the brakes to get them to work. I assume there must be some air in the system. Perhaps in the callipers themselves?

Any suggestions on how to solve this if i am not getting any air out the nipple?
Click to expand...
thats the best way of bleeding, you might need a few pedal strokes to clear a line,does reservoir bubble when pedal is pumped, some new calipers retract after pedals pressed meaning pads are slack requiring 2 pumps to take up the slack, it can often be remedied by lengthening servo push rod
 
Ok, so i went and purchased a pressure bleeder. Its the kind you screw into the reservoir and pump up to pressure. I then bled the brakes again. Started front nearside (furthest from reservoir), then front offside. Rear nearside (furthest from manifold on rear axle), then offside.

I put through 1.5L of brake fluid and not one bubble came through.

Went to pump the brakes and still the same. Even stationary, pump the brakes until they get hard. Release and then have to do the same again as its soft as anything.

I then went and got my help to pump the brakes, then press really hard until the pedal wouldnt go any further. Then start again. While this was taking place, i looked at every union and nipple in turn. No sign of bubbling, oozing, nothing. The only thing i could see happening was the front flexi pipes move a little as they come under pressure.

So any other suggestions? Still likely to be air? Jamesmartin - does your comment still stand with the above info? I'll look up how to lengthen the servo push rod....
 
Any suggestions would be much appreciated. I've missed the last couple opportunities for off-roading, so keen to get out on this months one, which is tomorrow!

I have the afternoon off work, so really keen on getting this resolved or i'll miss this months too ...
 
I take it that the engine is running whilst you're bleeding?
If not, they don't, and when you put your foot on the brakes, is the engine running?
You need the servo to work otherwise you get next to no braking!
Simple things often get overlooked! ;);)
 
Rorie said:
Ok, so i went and purchased a pressure bleeder. Its the kind you screw into the reservoir and pump up to pressure. I then bled the brakes again. Started front nearside (furthest from reservoir), then front offside. Rear nearside (furthest from manifold on rear axle), then offside.

I put through 1.5L of brake fluid and not one bubble came through.

Went to pump the brakes and still the same. Even stationary, pump the brakes until they get hard. Release and then have to do the same again as its soft as anything.

I then went and got my help to pump the brakes, then press really hard until the pedal wouldnt go any further. Then start again. While this was taking place, i looked at every union and nipple in turn. No sign of bubbling, oozing, nothing. The only thing i could see happening was the front flexi pipes move a little as they come under pressure.

So any other suggestions? Still likely to be air? Jamesmartin - does your comment still stand with the above info? I'll look up how to lengthen the servo push rod....
Click to expand...
it does, some new calipers have pistons that retract meaning 2 pedal presses are needed to get a hard pedal
adjusting the servo rod increases effective pedal stroke , if done too far brakes will apply themselves as you drive along as servo is activated
do you have bubbles in the reservoir when pedals pumped this shows poor master cylinder seals,which might not be evident during pressure bleeding
 
Engine hasn't been on when bleeding. I assume that's right? Typo on your post should say 'then dont'?

I took it for a drive up our road and found the issues, so engine was running then.

For bubbles in reservoir, I assume cap should be on reservoir? Engine off, push brake pedals and look for bubbles? I'll do that tonight.

Any guidance for adjusting servo rod? Not found anything of use online or in workshop manual
 
The engine should be running when you bleed the brakes, as the servo needs to be active.
If the engine isn't running you don't get the servo helping!
 
Rorie said:
Engine hasn't been on when bleeding. I assume that's right? Typo on your post should say 'then dont'?

I took it for a drive up our road and found the issues, so engine was running then.

For bubbles in reservoir, I assume cap should be on reservoir? Engine off, push brake pedals and look for bubbles? I'll do that tonight.

Any guidance for adjusting servo rod? Not found anything of use online or in workshop manual
Click to expand...
easier to see with cap off,
undo the 2 x m/c to servo nuts pull m/c away just enough to gain access to servo rod ,get some one to hold pedal fully down or wedge it hold rod with some pliers etc (as it isnt very securely clipped in)wind adjusdter n the end 8mm iirc anti clock wise ioe out a couple of turns, refit m/c and try it usually takes a few goes to get right ie not too short or long,
 
jamesmartin said:
it does, some new calipers have pistons that retract meaning 2 pedal presses are needed to get a hard pedal
adjusting the servo rod increases effective pedal stroke , if done too far brakes will apply themselves as you drive along as servo is activated
do you have bubbles in the reservoir when pedals pumped this shows poor master cylinder seals,which might not be evident during pressure bleeding
Click to expand...

THis is spot for on - my new calipers kept retracting due to the new rubber boot and seals (all I could think of) giving me a rubbish pedal. To get round it I took out the pads and put a piece of wood in there then pushed the pedal to push the calipers out more than they would with the pad in, i then put the pads back in, easing the piston back 'just enough' that the pads were a tight fit - bingo, good pedal.
 
Ok, so perhaps a school boy error in not having the engine running! I'll try again this afternoon with the engine going and hopefully that will solve it.

If not, then i'll look at the servo rod.

In regards to the cap of the reservoir - I thought I had to keep this on to get pressure while pressing the brakes? So when bleeding, i'll need to have the cap on?
 
I've always found bleeding works best if you start at the furthest point - usually rear nearside. I've never needed the engine on though, and I've bled LWB and SWB successfully. The pressure bleeder is a good call.
 
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