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

[buckroseau]

Finally getting back to this. I just finished a rear axle swap out of a 97 c3500. Also all new brake hardware and wheel cylinders all the way around. So, I essentially had every brake line in the system opened up.

Bought an pneumatic bleeder yesterday and still getting my ass kicked on this now. I got fluid to start pumping out the rear cylinders with the bleeder, but I can not get anything out the front. I installed a new slave cylinder on the clutch as well and was able to get that bled out and working. But, just can not get fluid to come out the front. This isn't rocket science, at least I didn't think it was?

Matt

[luvbowties]

Originally Posted by buckroseau

Finally getting back to this. I just finished a rear axle swap out of a 97 c3500. Also all new brake hardware and wheel cylinders all the way around. So, I essentially had every brake line in the system opened up.

Bought an pneumatic bleeder yesterday and still getting my ass kicked on this now. I got fluid to start pumping out the rear cylinders with the bleeder, but I can not get anything out the front. I installed a new slave cylinder on the clutch as well and was able to get that bled out and working. But, just can not get fluid to come out the front. This isn't rocket science, at least I didn't think it was?

Matt

Matt, what happens when you attach your pressure bleeder to one opened bleeder screw at a front caliper and try to pump fluid backwards & up into the master cylinder?
Sam

[luvbowties]

I've gotta share this: about 2 months back I had a highly-modified 1960's C10 coming in to install a new master cylinder. Owner had tried, but couldn't get any pedal. He'd told me it had disc brakes from what he thought was either a 71 or a 72 C10 & had worked fine for 2 years or so. So I bought a pair of these, but Dorman brand, in advance from O'Reilly's.

>> http://www.jegs.com/p/Russell/Russel...44478/10002/-1 <<

Wanted to buy 2 for the rear also, but they had no listing for rears. Anyhow, these front ones worked like a charm, costing about $10-$12 for a pair; Dorman shows a quantity of 1, but meaning 1 pair in a blister pack.

Was quite nice to crack fronts[one at the time--didn't want to really force my luck trying both at once] a tad, go around & pump pedal twice, back under & tighten screw back up. Had the customer pump pedal while I did the rears, in usual manner. Naturally, customer did not mind the extra $10-$12, as he "kept" them, installed, when he left.

BTW/follow-up: I measured the bleeder threads on rear wheel-cylinders & ordered a pair for the rears of "our trucks", on Ebay. Will one day install these on either mine or another's truck & verify they do as well as fronts, & report back. In the meantime, I think they are also sold by Advance A/P, Jeg's, Summit's and other online sites I have not done business with. All ap's seem to hover around the 10-12$ per pair range. **Be careful, as some sites sell what looks to be identical, but for around twice the price.
Sam

[65 C20]

Have the rubber flex hoses been replaced in the last 20 - 50 years.
Even if they are not cracked on the outside they can be deteriorated on the inside and plug up. You could crack them on the down side and see if you get fluid through them while pumping.
Just a thought.
.

[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

[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