Installed a new M/C, doesn't work at all, what am I missing??

[luvbowties]

Originally Posted by buckroseau

Ok messed around with this a bit tonight. As I said before, I can vacuum bleed the rear cylinders and get fluid to come out. But, nothing will come out the front.

I opened the line again up front where the soft line meets the hardline, right by the swing arm. I held the vacuum bleeder up against the hardline, and I could easily get fluid to pull though the vacuum bleeder. I then took my air hose and blew through the soft line while the bleeder screw was open on the wheel cylinder, air came out. So, at this point I'm thinking there is now way it can't work. Put everything back together and tried again...nothing.

Thought I would try something a little unconventional. I took the old cover off the MC and drilled a small hole in it. I then welded an air fitting to the top and hook up the air hose. I opened the air valve and pressurized the MC with the hope or thinking it would force brake fluid out the front bleeder screw. Once again, nothing. Air leaked out around the reservoir cap but nothing came out the bleeder.

As far as pumping the pedal, I tried that. It just won't build pressure so nothing I can really do with that idea.

Matt

Matt, several thoughts just at random. Does the style & specs of the m/c offer enough volume to operate ALL the braking capacity your brake system, as a whole, now has? [Seems I recall you swapped in a newer rear end, like a 3/4-ton, which likely used discs on front. It also may require a much-increased volume of fluid. This should be studied carefully: "We can't very well farm 100 acres with a Shetland pony".] Did you try pumping, via mc, to see if it would pump fluid thru hard line while you had them--hard & soft lines--apart? I think this is a must at this point, just gotta be tested. Can you 'block off' rears & try bleeding just fronts? This may narrow down variables & convincingly show which end is the trouble-maker. We all tend to be blaming front for all the pain, when rears could be the source. Another test: break apart soft-&-hard line. Put a tube from soft end into jar of fluid. See if your vacuum pump will vac. fluid from jar thru soft hose & thru bleeder: I'm betting some amount it won't do it. You said and I agree only partly, subject to enclosed, suggested, further tests, "So, at this point I'm thinking there is now way it can't work," But it defies that 'fact'. Another mentioned replacing soft hoses. I agree. That's gotta be done, imo. All other lines are static--do not move/flex/bulge when fluid flows under pressure. Soft lines are dynamic/changing, as they do all 3 things hard ones don't. They do crazy things, like even rotting inside & allowing a 'peeling piece' to act as a 1-way valve & lock up one front wheel cylinder.

Your tests so far do NOT push fluid thru soft lines, just air. Tests also do not vacuum fluid thru soft lines--either all way from master OR from where you took apart one where soft meets hard.

Sorry if my thoughts seem to wander, but your problem has become mine. And I wish to cover all possibilities. At this point, my bet is on either (1)a m/c that is pumping barely sufficient volume to push fluid thru a least-resistance path which is the rear bleeders. (Blocking off front lines would verify if m/c can not only flow fluid thru rear bleeders but also operate the rear brakes with good pedal--and determine if m/c is good or bad or 'insufficient'.).......Else (2) front flex hoses are defective.

I'm following thread and looking for a soon-discovered solution.
Sam

[luvbowties]

Originally Posted by luvbowties

Matt, several thoughts just at random. Does the style & specs of the m/c offer enough volume to operate ALL the braking capacity your brake system, as a whole, now has? [Seems I recall you swapped in a newer rear end, like a 3/4-ton, which likely used discs on front. It also may require a much-increased volume of fluid. This should be studied carefully: "We can't very well farm 100 acres with a Shetland pony".] Did you try pumping, via mc, to see if it would pump fluid thru hard line while you had them--hard & soft lines--apart? I think this is a must at this point, just gotta be tested. Can you 'block off' rears & try bleeding just fronts? This may narrow down variables & convincingly show which end is the trouble-maker. We all tend to be blaming front for all the pain, when rears could be the source. Another test: break apart soft-&-hard line. Put a tube from soft end into jar of fluid. See if your vacuum pump will vac. fluid from jar thru soft hose & thru bleeder: I'm betting some amount it won't do it. You said and I agree only partly, subject to enclosed, suggested, further tests, "So, at this point I'm thinking there is now way it can't work," But it defies that 'fact'. Another mentioned replacing soft hoses. I agree. That's gotta be done, imo. All other lines are static--do not move/flex/bulge when fluid flows under pressure. Soft lines are dynamic/changing, as they do all 3 things hard ones don't. They do crazy things, like even rotting inside & allowing a 'peeling piece' to act as a 1-way valve & lock up one front wheel cylinder.

Your tests so far do NOT push fluid thru soft lines, just air. Tests also do not vacuum fluid thru soft lines--either all way from master OR from where you took apart one where soft meets hard.

Sorry if my thoughts seem to wander, but your problem has become mine. And I wish to cover all possibilities. At this point, my bet is on either (1)a m/c that is pumping barely sufficient volume to push fluid thru a least-resistance path which is the rear bleeders. (Blocking off front lines would verify if m/c can not only flow fluid thru rear bleeders but also operate the rear brakes with good pedal--and determine if m/c is good or bad or 'insufficient'.).......Else (2) front flex hoses are defective.

I'm following thread and looking for a soon-discovered solution.
Sam

Matt, just for curiosity I checked m/c's for your pickup and for '97. Seems '97 uses a 1.25"(1 1/4) bore vs. yours a 1.125"(1 1/8) bore. Comparing equal length pumps of each m/c means the '97 pumps 1.23 times as much volume of fluid as yours.

The '97's use of discs on front would dictate it pump considerably more volume. Add the use of longer strokes enabled by power brakes. [When we add boosters to our older trucks, we drill a 1.5" lower hole in brake pedal where m/c push rod attaches, giving a harder push PLUS a longer stroke to m/c for same distance pedal is depressed.] Just perhaps the '97 also uses such a longer stroke--just guessing/theorizing, as I have no clue--if it incorporates a 50% longer stroke, then the additional volume would be 1.23 X 1.50% = 1.845 times as much. Almost double the volume. Dunno if extra volume is all taken up by discs or discs PLUS '97 rears.

ALL THIS PURE THEORY, ADDED TO EVEN MORE SPECULATION, giving more............. food for thought.
Sam

[buckroseau]

Ok, this is where I'm at. Yesterday I ordered up new soft lines for the front end. Had to work today, but on the way home this evening I picked them up. After some family time, got everyone to bed I was able to sneak an hour in on this thing tonight.

I pulled the old lines out first. After I got them off I attempted to blow through them with my mouth vs the air compressor: I could not. I was able to blow through the new ones easily. At this point I'm thinking this is going to be easy. Installed the new ones, cracked the front left bleeder and hooked up the vacuum bleeder and away I went. ............nothing.

Frustrated at this point I hooked up my custom M/C cover so I could pressurize it. After turning the air on I cracked the driver side bleeder, air came out for a while then solid fluid. I closed that bleeder and then cracked the right front bleeder....nothing. I increased the air pressure a couple times and finally was able to get fluid to come out that one as well. Air for a few seconds then solid fluid. At this time I'm thinking I should be able to get some pedal pressure.....even a little. Stepped on pedal, right to floor, no resistance. I pumped it for quite a while, nothing ever changed.

I thought I would hook up the vacuum bleeder up front now just for fun, see if it will pull fluid through. Drivers side it pulled fluid through just fine. The passenger side would not pull any fluid through the vacuum bleeder.

I also wanted to try bleeding the rear again. That pulled fluid through the vacuum bleeder just fine days before, just thought I should try it again for some reason. Hooked up the bleeder...nothing. So, now I'm scratching my head wondering what's going on. I hooked up my custom pressure cover and pressurized the M/C again, fluid came out the rear solid. I closed the bleeder and gave the pedal another pump....absolutely no resistance. Pumped for a while, but still nothing.

I realize at this point I still may have some air in the lines, but I just can't believe I can't get a wheel cylinder to even move?? Or even a bit of resistance at the pedal??? The clutch is in the same reservoir and I was able to bleed that out fairly easily a week ago.

At this point I'm not sure what to try. The only thing I can think of changing out is the M/C itself.

Matt

[65 C20]

This might be a long shot.
When you are doing the vacuum bleeding or the air pressure thru the master do you have the brake pedal depressed ?
I am wondering if one of the seals or 0-rings have partially come off of the piston inside the master.
If you are taking the master off to replace, take it apart before you order another one and see if everything looks like it should.
Just a thought, you have done just about everything else.

[luvbowties]

>>You said, "Frustrated at this point I hooked up my custom M/C cover so I could pressurize it. After turning the air on I cracked the driver side bleeder, air came out for a while then solid fluid. I closed that bleeder and then cracked the right front bleeder....nothing. I increased the air pressure a couple times and finally was able to get fluid to come out that one as well. Air for a few seconds then solid fluid. At this time I'm thinking I should be able to get some pedal pressure.....even a little. Stepped on pedal, right to floor, no resistance. I pumped it for quite a while, nothing ever changed.".......This bold sentence points to possible obstruction between mc and rf wheel cylinder. System also acts as if trash is floating around inside lines, affecting both fronts and rears.<<

Why not replace the mc to hopefully correct all? Quickest test at this point.

If no joy, now, why not replace the mainline to the tee, the tee itself, and the front solid lines. Not toooo much work, but could be old front soft lines have left deteriorated remnants in the system. Would be good test to use just an elbow in place of tee, temporarily. This would allow testing mc on a "smaller system"; these lines, 50 years younger, cannot hurt. While broken apart, blow thru all lines serving front to clean out any possible debris still remaining.

Now, the new mc on the smaller system has gotta work. When verified, only you can decide whether to replace lines going to rears.
Hope some of this helps.
Sam