Bleeding Issue

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72CS

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Hi all,

I decided to finally change out my brake fluid but I am having the following problem. I can't get the brake fluid to flow (bleed) from any of the calipers. I have tried a pressure system on the reservoir as well as a vaccuum system at the bleed nipples, all I got was about a thimble full of fluid. I even tried the old fashioned way with a friend at the brake pedal. The pedal itself is fully retracted. I have a hard time believing all the lines are clogged, anyways the lines are not that old.

Prior to this the brakes were working quite normally.

Any ideas?

Thanks all.
 
Brake lines?

Do you have the old original rubber brake lines? If so I would suspect them and replace with stainless steel.
 
The previous owner had installed stainless lines (although not sure when). The rest of the system looks to be in good shape as well. I'm pretty sure all the hard lines were replaced, not sure about the master cylinder but from the outside it looks like it was at the very least cleaned up.
 
Did you have brakes and a good pedal prior to bleeding? If you did have brakes, do you have calipers hanging up?

If you had calipers hanging up, fluid is going in but can't get back out, indicating swelled hoses. It would be odd if they had all swelled shut at the same time, but stranger things have happened.
 
Stainless steel lines

The SS lines are still rubber inside the SS; therefore susceptible to deterioration. Just saying; don't discount the possibility because they are SS. FWIW
 
Non bleeding calipers

Likely M/C, if all 4 corners are not bleeding ( return spring, dirt, etc.). Collapsed flex lines usually show up on a corner (dragging brake), not all 4 at once.
 
Regular problem at my shop- have you removed each bleeder screw and run a big sewing needle into bleeder screw hole?
 
RogerB said:
The SS lines are still rubber inside the SS; therefore susceptible to deterioration. Just saying; don't discount the possibility because they are SS. FWIW
Click to expand...

Beg to respectfully differ with you. In my limited experience, stainless clad flex lines are extruded plastic - sheathed in metal. Not saying rubber couldn't be involved. Only that I haven't encountered it. Just like original stock rubber reinforced lines, they are not impervious to defects, wear or damage. They can be kinked, the metal can fray and expose the plastic to further damage and the plastic can be damaged if it is repeatedly stressed by allowing the calipers to hang supported only by the lines.
SpeedFlex_cut.jpg


http://www.mpsracing.com/products/Earls/Speed-Flex.asp

The easiest thing to do is remove the bleeder screws as suggested by SFDon and look carefully at the side orifice/s at the insertion end of the screw. They may all be deformed/compressed due to over tightening. Over tighten one - over tighten all?

On the other hand, if you want to eliminate the calipers as an issue you could see if there is any flow -upstream of the caliper - by loosening or removing a flex hose at the caliper.

Just a thought.
 
Thanks all for the suggestions. I did remove at least one of the bleeder nipples to confirm that it wasn't clogged. I havn't checked the bleeder screw holes, so I will look for a sewing needle tonight (or similar). If this doesn't work I guess I have to start removing hoses to see where there is, and is not, any flow.

Is there anything obvious in the MC that would cause this effect?

Cheers,
 
You could use a coat hanger...

If you had a functioning brake system and MC prior to your fluid change then odds are MC is OK.
re: the MC does it depress and return or is it frozen/locked in fully depressed mode?? The MC would have the seals dried/degraded and stuck in place so as no motion which wold cause no fluid flow??? Open a line at the MC and push/pull the brake pedal/bar; any flow?
Jon
 
Thanks everybody for the suggestions. the problem is resolved for now.

The MC piston (s) was frozen all the way down cylinder cutting off the flow from the fluid reservoir. This seems to have happened when attempting a bleed using the brake pedal. I was able to release the shaft by pulling the MC about a 3/4" from the booster and then just manually pulling out the shaft. (sounds like this isn't the first time this has happened)

After resolving the MC issue I noticed that when bleeding the brakes the the top nipples on the front calipers did not flow fluid very well compare to all the other nipples. Is this normal?

Also, I should probably think about rebuilding the MC: Where can I get a MC rebuild kit, and how do I know what to ask for (I don't know if the MC I have is origianl or not, it doesn't seem to look like the one n the manual)

Thanks again
 
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