bleeding brakes

93 240. Just installed new rotors and calipers all the way around(this will be my sons car (17) so believe me,it will need good brakes) Master cylinder functioning fine before swap out. Bled the brakes per Haynes repair manual instructions. Plenty of brake fluid in master cylinder when done. Im pretty sure I got all the air out of the lines. Start car. Very minimal brake pedal resistance when pressed. Will go right to the floor. If I pump the pedal-resistance gets no better but engine idles roughly/drags. What did I do wrong?

[Erling]

My knowledge is limited to non-ABS cars, but two things spring to mind:

(1) When installing the front calipers, are you sure you got them right left/right? If not, air will be trapped inside when bleeding. (NB: ABS calipers may be different.)
(2) If you pedal-bled, did you push the pedal all the way to the floor? On older cars like ours, this may destroy the seals between piston and MC. (There may be rust on the cylinder walls outside of the normal operating area.)

[Peter D]

I use a spare master cylinder cap that I have inserted a tyre valve into and use 5 psi of commressed air to presuurise the full tank then blled one wheel at a time, furthest first. You will need 1 1/2 to 2 litres of fluid to do the whole job and do not blow the header tank off the master cylinder.

With an assistant the best way is put your spanner on the bleed niple and then the pipe into a jar, now nip the screw up and get the assistant ho press on the brakes you crack the nipple open and let it flow out until your assisant calles Down you nip it up ( only one quarter required ) and you call Up, repeat this until you can no longer hear the little bubbles spitting through the just cracked up bleed valves. Repeadetly check fluid level or arrange an auto top device. A sealed container with a short piece of 1/4 inch pipe into the header will allow air up the pipe when the end of the pipe is exposed i.e. 1/4 empty and fluid down to fill the header.

Do this to both circuits all wheels then repeat until no more air is heard. Regards Peter

[Clifford Pope]

Volvo forums the world over are littered with threads like this - "my brakes were OK until I overhauled and bled them, now they don't work despite repeated bleeding".
Ehrling is probably right - the master cylinder is very prone to this kind of localised internal corrosion, and as he says, pressing the piston over unused sections of bore very frequently damages the internal seals so it stops working.
With hindsight, never press a Volvo brake pedal beyond its normal range of travel, but pressure bleed as Peter advises.
You may well need a new MC now.

Other sometimes difficult features are the "octopus" pressure warning valve, and the two limiting devices in the run to the rear brakes. Both can be stubborn places for air locks if the fluid has been drained totally.
Another Volvo tip - never dismantle more than one bit at a time. Plug the pipe, replace the caliper etc, bleed that caliper, then move on round. Change the fluid by displacement, not by draining.
There are threads on bench-bleeding MCs, although there is some dispute over this issue.

All, I repeated bleeding the brakes. Absolutely minimal brake pedal resistance when I finished. I will now replace mastercylinder.
My question is?- should I purchase a MC rebuild kit($45.00) or a new (rebuilt) MC ($160.00) and just swap it out. How difficult is rebuilding the MC myself with the kit? Thanks for any advice. Brian

Hi
this may be a stupid question but did you bleed the brakes in the right order?
Mechanical with pressure bleed:
Start on RF open all bleed nipples, 5 pumps, repeat at LF then LR then RR if fluid totaly lost from master cylinder onlt pump 3 times.
If no Pressure bleed: then as above with 5 pumps on each pedal.
(direct from Volvo technical training liturature)

Hello, I did not bleed brakes in that order but started furthest from MC and worked toward it. In doing this procedure, the reservoir lost almost no fluid, maybe an ounce. The brake fluid really comes out of the nipples weakly, not with any force. I really think I'm not getting any compression from MC. Does this seem like a reasonable guess as to whats going on?

You need to start at the nearest the MC as you will be compressing the air in the rest of the system give it a try before you replace the MC as another bottle of fluid is cheaper than the MC and you will still have to bleed the system again anyway. how would you feel if you replaced the MC and it was just the bleeding system?( excuse the punn)

I give up. Have bled the sytem mutiple times with assistant. Still no brake pedal resistance. Replaced the MC, re-bled. Still no resistance. Don't believe the system was ever completely dry as I put plastic wrap under MC reservoir cap while doing work and lost minimal fluid. Anything additionally that I can do before I hook her to a tow for a ride to the shop? Some weird airlock as you mentioned? I don't see any leaks of fluid anywhere. Thoughts? Thanks

[Clifford Pope]

Silly thought, but I do remember a similar post from somewhere once, and the answer was that two of the new calipers were interchanged left/right. Apparently they fit, but the bleed nipples then aren't at the top so they are impossible to bleed properly.

I've never drained out a system so I don't know if this is true, but I have read of troublesome airlocks by the pressure limiting valves on the brake lines to the rear. The lines do a kink near this point, and the nature of the pressure limiter tends to let air lodge there rather be expelled. I have read advice to raise the rear of the car as high as possible.

I have also read someone's suggestion in similar circumstances to block off parts of the circuits to identify the location of the air lock.I'm not quite sure how this would be achieved.

I have found when fitting a new MC that it was quite difficult to "wet" all internal surfaces - air tended to stick in places, and by tilting, pumping and shaking I kept getting a bit more air out. Hence bench bleeding. But then again, others have disputed that doing this has any value.

Final thought - with all this bleeding, is it new fluid, or the old (but still new) fluid re-circulated? Fluid needs to stand for quite a while to let it de-airate.