Need Brake Bleeding Help

[N233TX]

'75 Midget 1500 Fluid mysteriously lost from system (none on floor or apparent mess on wheels.) Proceeded to bleed as per manual. Cannot get fluid to either flow into bleeder jar or suck back out when pumping pedal. Tried my EZBleed and could neither push fluid in or suck any out. Can't get a helper right now to pump the brakes. Don't see any broken lines.

Right now the master is topped off and the bleeder tube is submerged in the bleeder jar and nothing moves when brake pedal is repeatedly depressed and released. I've successfully bled the brakes on this car before...no problem.

I'm thinking the master is shot somehow but it has less than 1,000 miles (and 10 years) on it. Brakes were fine when last driven 2 weeks ago.

Could someone who really understands the system offer some trouble-shooting advice here?

TIA Jim

 

[Trevor Jessie]

No fluid on the carpet/floor mat?

 

[Deleted member 8987]

FIRST thing I would do is ensure there is no air lock in the master.
Pop the line on the mater outlet, hold you finger over it while an assistant slowly presses the pedal, allowing any air to escape by releasing finger, place finger firmly on opening while pedal is released. Do it several times. If you get flow, re-attach line, crack it and press pedal, tighten, do it again until air stops popping out around the line.
Same as bench bleeding a master, which you have to do new.
Dual master, I'd do the port closest to the pedal first.
1975.....do you have a booster?
Pull the master. Look down inside, see of you have a booster full of brake fluid.
If so, remove it, drain, it, flush it with some spray brakekleen, re-install, then NEW master.
At least that's what I have done for many years...successfully.
Dave

 

[N233TX]

Floor is dry. Will proceed with suggested fix. Never heard of an air lock. Would that create the symptoms noted? e.g. inability to either extract or inject fluid?

 

[Deleted member 8987]

Running fully out of fluid as you stated initially will do it.
"Prime the Pump" is another term.

When you buy a new domestic master cylinder, there are instructions for bench bleeding. You MUST do that or you'll by stroking that pedal for days with no results.

Not saying that's it....but one thing you'll know immediately is whether the master works or not, and proceed from there.

 

[JPSmit]

May i also suggest you pull the switch assembly and clean it. ( that brass piece that dircts flow to the brake lines.) i was stunned how much crud there was in it. IIRC i also put a nipple on it and bled the brake to there before going on to the hubs.

 

[N233TX]

OK, weather delays and back to the problem... Took poster advice to inspect and rebuild the switch assembly. It was very clean but cleaned as per and installed new o-rings. Figured it would be a good idea to rebuild the master while I was at it. This rather challenging procedure revealed a clean bore and I carefully installed the myriad pieces, constructing fixtures to do so, double-checked the assembly and successfully bench-bled the master using clear tubing to remove all air bubbles. Cussed my way through master re-install, spilling the requisite amount of fluid on the rag under the brake pedal.

Current situation: starting at right rear bleeder valve, no-go on traditional bleeding or EZ Bleed vacuum or pressure...no fluid at all. Ditto left rear. Can't get fluid to push up the line (my favored way to bleed). Pumping brake pedal moves some fluid out of both front bleeder valves and fluid level goes down in reservoir.

The rear brakes on the '75 incorporate hard tubing directly to the wheel cylinders so there are no rubber hoses to replace. Should I try disconnecting these and seeing if I can get fluid down the line? I can't imagine a scenario where *both* rear brakes will not bleed properly. Of course I can't figure out how the system originally bled down on its own without leaving a puddle on the shop floor...

I need some troubleshooting ideas before I start tearing things apart. TIA Jim

 

[dklawson]

... rebuild the switch assembly. It was very clean but cleaned as per and installed new o-rings.

I cannot comment on why the brakes are not bleeding except that I suspect a problem in the master cylinder. Based on the symptoms I am surprised you did not find fluid in the driver's footwell.

My real reason for posting is your comment that you installed new o-rings. I am not familiar with a switch assembly on the brakes apart from the PDWA. If the o-rings you installed are in contact with brake fluid you may have introduced a new problem. Regular o-rings are Buna-N (Nitrile). Buna is compatible with DOT-5 fluid but not DOT-3 or -4. If you are using DOT-3 or DOT-4 you need to use seals made of EPDM.

 

[SaxMan]

Maybe the bleeder valves themselves are clogged? It wouldn't take much to jam them up. If the clog was in the line actual line, I imagine you wouldn't have any rear brakes at all.

 

[bthompson]

...which begs the question, do you have rear brakes at all? If the flexible hose over the axle to the rear hard lines is deteriorated and gummed up internally, you could have no rear brakes and never realize it; the fronts do a good job on their own. (Go ahead, ask me how I know)

If the rears work, then the problem, like Sax says, most likely with the bleeder passage or the valves.

 

[N233TX]

Thanks y'all. O-rings that went into the compensating valve were in the rebuild kit from Moss so they should be brake fluid compatible. Bleeder valves were inspected and found OK. Gonna check that flexible line over the axle. Can't find that part listed in either Moss or Vic. Can somebody give me a part number? What associated parts do I want to get? This hose is almost 40 years old and it sure looks like a likely culprit given that both rear lines seem clogged...

 

[Rut]

Heres a set from Moss.
Rut
https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=115451

 

[Bigomudders!]

Hello having similar problem, but I clamp rear hose and pedal is at the very top great pedal. no leaks in rear system at all. Bleed system thinking I have a air out and pedal will go to floor a couple of pumps and its back at the top and holds DOES NOT SINK. Wait 10 seconds and pedal goes back to the floor. HELP

 

[BobHaskell]

Hello having similar problem, but I clamp rear hose and pedal is at the very top great pedal. no leaks in rear system at all. Bleed system thinking I have a air out and pedal will go to floor a couple of pumps and its back at the top and holds DOES NOT SINK. Wait 10 seconds and pedal goes back to the floor. HELP

Are the rear shoes adjusted to the drums? If you set the parking brake does the pedal still go to the floor after 10 seconds?

 

[Bigomudders!]

Are the rear shoes adjusted to the drums? If you set the parking brake does the pedal still go to the floor after 10 seconds?

yes

 

[Bayless]

Not sure I understand "clamp rear hose" and how that relates. But, If you have pedal and it slowly sinks to floor then the fluid is going somewhere. About all that can happen is a leak somewhere in the system and you should find brake fluid. Otherwise it is leaking internally inside the master cylinder, a common problem as they wear. Having to pump the pedal still sounds like rear brakes badly out of adjustment.

 

[BobHaskell]

Not sure I understand "clamp rear hose" and how that relates. But, If you have pedal and it slowly sinks to floor then the fluid is going somewhere. About all that can happen is a leak somewhere in the system and you should find brake fluid. Otherwise it is leaking internally inside the master cylinder, a common problem as they wear. Having to pump the pedal still sounds like rear brakes badly out of adjustment.

One can close off the rear brakes by clamping the rubber hose that feeds the hard lines on the rear axle. If he has good pedal with the rubber hose pinched close, then the problem ought to be somewhere with the rear brakes. Either too much motion (shoes out of adjustment) or a leak.

 

[BobHaskell]

yes

Have you checked the rear wheel cylinders to make sure that neither one is frozen? That the pistons move freely (in and out).

 

[JPSmit]

what year car do you have? I ask because I wonder if it is still air and specifically related to the splitter for the dual system. I find that when people rebuild these puppies they almost never clean it (including me) and it was disgusting! I would still be inclined to be looking for air in the system.

 

[Bigomudders!]

Have you checked the rear wheel cylinders to make sure that neither one is frozen? That the pistons move freely (in and out).

yes new wheel cylinders, new shoes and hardware but OE drums. I'm really starting to believe the drums are way out of spec causing the need to pump pedal.