I'm gradually getting the car back on the road and have recently rebuilt a rear caliper. Whilst bleeding this caliper, progress was being made however the pedal now goes to the floor each time and a slight gurgling sound can be heard when I open the bleed screw but hardly any fluid comes out. This has been going on for quite a while with no change. The front brakes do work but neither of the back brakes. Should I continue or do I need to do something else?

lots of air in the system...and not enough fluid ..but you knew that already right? keep resivor full and try a power bleed system or the old two man method of pump and hold ,release valve and repeat.. and start at the right rear wheel, then left, then right front,then left front ....then do it all again until your happy with the pedal ,,dont push the pedal to the floor it can mess something up in the MC I think i heard something like that ..The brake pros will chime in soon and will be able to explain it better....it can be a real chore getting the pedal back . Have plenty of fluid on hand..a clear bleeder hose on the valve so you can see the fluid and bubbles coming through and a jar to let it dump into...dont get it on any painted parts it eats paint...good luck..hope that helps


MikeC

The pedal has gone to the floor, lots of times now. There is no pressure. Have i broken the master cylinder?

Check this site for McMarks long tube method.

Im not sure ...silly ? but you did keep the resivor full ,sounds like ya run outta fluid....... really thought someone that knows more then me would have chimed in to help ya out ...
MikeC

Clogged master cyl on the rear ports due to " pushing pedal all the way to the floor" rust and other debris . Happened to me last month' has to replace it , and all worked well ,

Good luck

If thats the case ya got some work to do ...Mr shea please pick up the white courtesy phone ....is his MC shot
MikeC

If you have been bleeding the system properly and this keeps happening and there is no other clear culprit- IE leaking hose somewhere, then I would take a look at the MC to make sure that all the connections are in and tight. if this is an old MC, I would take it out, and look at the seals, if in question replace it!

No pressure at pedal = blown MC seal, per: PPetion



True, except "balance valve" on the the line, located underneath engine at firewall that regulates pressure to rear calipers. Diagram shows MC and valve below:
Click to view attachment

Here's something else:


Pelican Tech Article: "Bleeding Brakes"

Yeah, your MC is probably dead. I usually just replace the whole system on older, unknown-history cars. It's the safest route.

I bet if you look under your pedals there is some brake fluid that's leaked out the front of the MC.

IIRC, Jonathan at GPR has a good price on stock master cylinders. When you do replace it, make sure to bench bleed it for awhile first, or install it in the car, but plug the output lines instead of hooking up the calipers at first. Pumping the master cylinder without letting the pressure out to the wheels will force all the bubbles out of the MC first. If you don't do that you have a LONG bleeding process ahead of you.

Thanks for all the replies.

Thats just great, I needed another job to do on this car to stop me getting it back on the road!!!

I will be happier though knowing that it's done properly. I already have a new 19mm in a box. I'll replace the flexible hoses as well as the Master cylinder and get some new fluid too. Thanks for the tip to bleed the m/c first I assume it's all fairly straight forward.

You may search for instructions for bench bleed first then make sure you don't press the pedal to the floor again.

Am I correct in thinking becase it's new and not full of crud I can floor the pedal? I obviously don't want to trash a new m/c so want to be clear on this. If not, how far can I press the pedal safely?

I have never heard of the "dont press the pedal to the floor" thing before.

I did that on my last bleed and have no problems.

I am guessing it is really "Dont press the pedal to the floor with all of your strength".
Even then I dont see how you could damage it.

I have done that with every car I have owned and never seen a MC failure.

Stu

Old MC have a wear line, or crud line, whichever, from use. Pressing an old piston seal past that line can ruin it. I've done it. Others too.

New MC doesn't have that issue.

with Stuart. It's mostly a problem with older MCs.