Still no pedal after bleeding 93 Nissan 240SX

This relatively simple job has turned into a several MONTH long nightmare plagued along the way by one thing after the other from flat tires, dead batteries to suddenly failing jacks, etc. If my frustration seems BIG, that's why. I'm at "wits end", I've tried all I know, I'm out of ideas, there's now snow on the ground and I still don't have a car! I can really use some help!!

Heres the story:
Brakes were fine - not "ideal" but OK. Brake fluid level would drop over a week or two and turn on the idiot light.
I found a corroded, ruptured brakeline (to rear about at middle of car). I wanted to replace the entire line from Master Cylinder to the "splitter" (terminology?) in the back but fittings too corroded. Not easily accessible and I couldn't remove. Didn't want to replace all the way to calipers so decided to patch instead.

Bought factory flared (20") section and flared the mates myself.
This MAY be significant: This was my first attempt at double flares and I honestly don't know if I know what I'm doing. I practiced some on scrap brakeline. Some turned out crap, some OK. They didn't look like the diagram - all doubled over - but looked OK. Similar to the factory's. I guess I don't know exactly what the perfect double flare is supposed to look like. The replacement section looks pretty good. Have not found any brake fluid on lines at unions.

After repairs done, proceeded to bleed lines.

Tried usual pump and hold.
Didn't seem to be working well.
Badly vice-grip chewed-up Bleeder screws at a wheel or two made this difficult (especially with tube attached).
Hard to tell if fully opening/closing properly. (Eventually replaced all four bleeder screws.)

(A bit of advice. If you don't have a flare nut wrench, buy one! Don't even try to use a regular wrench, pliers or anything else. And if you already did and you've begun to round the edges, replace those bleeder screws right away! They're only a little over a buck each and it's still a simple job at this point!

For those that might come across this in the future searching for the right size bleeder screws, all 4 are:
M10 x 1 x 33 (30mm-35mm). )

I noticed that, while pumping, there'd sometimes be a bubble in the master cylinder.
I figured I introduced air into system by pumping with bad (not completely closed bleeder screws) I disconnected and "bench bled" master cylinder (while left mounted in car.) Bench bleeding seemed to be successful.

After master cylinder reconnected, "gravity bled" system.
First with calipers mounted, then unmounted hung by wire. Tapped with a hammer to dislodge bubbles.
Seemed to be working. Got a decent flow but at only 3 wheels (perhaps due to car not being level?)

Bought MityVac and tried vacuum bleeding.
Seemed to work. Gauge showed vacuum. Lot of bubbles then more fluid than bubbles. Kept master cylinder level up throughout.

We then did the pump and hold again with not much improvement.

Replaced all four bleeder screws. At this time it was more-or-less being "gravity bled" yet again and with a good flow at, I believe, all four wheels.

Vacuum bled again with better results-- though it never got to the point I expected; sucking 100% pure fluid with 0 bubbles.
I read this could be due to seal at connectors or bleeder screw threads (I did not wrap with teflon tape as some recommend.)


Regarding bleeding sequence:
At first, (with pump and hold) I did farthest to closest (RR RL FR FL). Vacuum bleeding recommends closest to farthest (FL FR RL RR). Tried both ways and in various combinations multiple times.

After vacuum bleeding, performed pump and hold again.
Some bubbles at first, then eventually only fluid! Looked very good!
Nice clean fluid coming out, master cylinder fluid level regularly dropping down and being filled up.
Everything appeared to be happening just as it is supposed to. I thought all was (finally) well!!

...but Still no pedal!! The resistance is not increasing at all. In fact, it may even be worse. I've got (almost) no brakes!

Why? Whats wrong?
What did I do wrong?
What did I not do that I should have?
Could it be that I didn't bleed them enough? or that I just don't know how to properly bleed brakes, afterall?

If bad flares on my patch are causing this problem wouldn't I find brake fluid leaking at the unions? I don't.

If my patch to the rear line is bad but the fronts and everything else is OK, shouldn't I still have at least some decent resistance in the pedal?


In case this matters, I did remove the rear calipers one of the times I did gravity bleeding but did not mess with pistons. I did disconnect line from caliper once for extra clearance when changing bleeder screw.
No instrument panel lights on.

I have researched this before posting and I was very surprised to find at the Nissan forum alone, (searching Suspension & Brakes using brake bleeding) about a dozen or so posts describe a situation very similar to almost identical to mine; coincidentally(?) more than a few were also 240's. In most cases, it seems the answer suggested is to bleed the brakes, which I've already done several times every way available to me or it's the master cylinder. I don't believe I had any master cylinder problem before so if there is now it's new, perhaps created by us during the bleed? I read that pushing too far down on the pedal during pump and hold bleeding can damage the master cylinder seals. Theres a chance my pumping helper may have done this. If that happened, would the symptoms (of damaged master cylinder seals) match my situation? If so, how do I confirm?

As I said, I'm out of ideas. I don't know what else to do but, whatever it is, I need to do it NOW!
What else can I try? Your help is very much appreciated and any advice or suggestions welcomed.

Otherwise, the next step must be to take it in to a mechanic; something I'm sure many of you understand my reluctance to do -- not only because of the expense but, especially now, because of all the thought, time and work invested! Not to mention the further destruction it will do to my self-confidence! (I'll find some other forum to post about my depression, feelings of failure, emasculization, damage to my self-confidence, self-esteem, ego, etc..)

Thanks a lot in advance for any help. Believe me, I will sincerely appreciate it!

 

Hang in there:

A brake system is pretty fundamental until you get into ABS stuff.

You have to have a closed hydraulic system. Closed to air, that is. Entry points to air are also exit points to fluid - which is how you typically find either leak. Brake lines, caliper seals/wheel cylinder seals, and bleeders are where air can get in and fluid can get out. Those all need to be wiped clean and dry and checked for leakage.

First, with the master in place and the bleeders closed, fill the master and systematically go from wheel to wheel to check for leakage as well as the lines.

If, it's hard to tell if you're getting seepage, wipe it clean, spray it with carb cleaner or starting fluid (which evaporates quickly) and powder it with baby powder or something similar.

Usually problems that surface are connected with what has been worked on so pay particular attention to the patch you put in and the bleeder screws for leakage. Considering what you have had disconnected and replaced, you would be starting out with a fair amount of air to bleed.

Once you have made the rounds, bleed the system - RR,LR,RF,LF - left side referring to driver side. If your system is fully closed, you will have pedal pressure if your master cylinder is good. If no pressure, think about replacing the master.

Hope this helps,

Bob

 

How about then, to expedite matters, that he get plugs for the master cylinder brake line threaded holes into the side of the master cylinder, and then see if the pedal goes to the floor if he steps on the brake pedal?

 

That sounds like a good idea. I'd never used that before, but it'd a good way to test the master. In doing so you would want to make sure your plugs fit the seats in the master cylinder ports.

 

very good point. Does the car have ABS? Not familiar with them furrin cars much and this seems to be old enough where it is not probable but....

also, I know that on a lot of GM cars, it was very possible to damage the master cylinder seals by pushing the pedal too far so special (unique) procedures were designated for those cylinders involved. Don;t know if those furrin cars had any similar problems but.....

Oh, and to the flare wrenched for a bleeder screw? Not a chance. I use a bleeder wrench, which is a full box wrench, 6 point, typically quite long (although I have had short ones as well)

 

Once upon a time I could not bleed my brakes
Turned out that I had put the front calipers on backwards.
This resulted in the bleeders not being on the top.
The fix was to put the calipers on the right way and then bleed.
It sounds like you did not replace anything so this should not be your case. If you did just get the car, it would be something to check.
On stubborn bleeds I have found another method that works.
Dont pump
Do everything slow mo
Have assistant slooowly step on brake pedel, and slowly open bleeder then close the bleeder.
Assistant then slowwwwly lets up on the brake pedal.
This is repeated until good flow comes out.
Everything is done slowwwww and eassssy and absolutely no pumping.

Gotta be something that can be done.
Hang in there and dont burst
Get back to us

 

Thanks a lot for your (prompt) responses. I do appreciate it. This is a pretty good, active forum!

"Hangin' in there" would be much easier if it were a different time of year or if I were nearer the equator! The weather's already lousy here (in Ohio, US) and I can't count on it improving much for a few monthes. Yes, there's a garage but no room in it for anything as big as a car!

(Nap, You're right; I misspoke.I guess I meant if not a proper bleeder wrench, at least a line wrench but definitely not pliers or vice grips, etc. -- except as a last resort to replace the bleeders.

As to whether or not I have ABS; yes, they just aren't as well defined as they once were.. especially now, around Thanksgiving!)


Anyway, I think my problem, in general, must be one of the three:

1. Master Cylinder problem
2. A leak in the hydraulic system
3. I simply haven't bled the system thoroughly enough or (I'm bleeding it incorrectly)

Do you guys concur? Have I left out another possibility?

1. If the master Cylinder is the problem I must have caused it because it's only a year or two old and it was fine before I started. I read that an easy way to check the MC is to "turn off the car and pump the pedal. If you get pressure, then it just needs bleeding. If you don't, its your master cylinder." If this is true, mine just needs bleeding as I can pump a dozen or so times still get nothing but, with the car off, get resistance at second press. On the other hand, someone else (a professional mechanic) told me this is not an accurate test.
   
   When I had the MC disconnected for bench bleeding, it seemed to be working; especially at first: bubbles went out, bubbles went in, bubbles out, bubbles in, fewer bubbles out, a few bubbles in...until there were no more bubbles. Does this not confirm the MC's OK or must it be under pressure?
   
   Regarding plugging the master cylinder ports, I tried once before. I couldn't locate threaded plugs and the little, generic, black rubber push-in type were a poor fit and would blow out with each press on the brake pedal.
   
   Besides, I'd really rather not disconnect the lines from the MC again both because the connectors already aren't in the best shape and because it'll set me back to square one with the bleeding. Is there a way to test it while still mounted/connected?
   
   
2. A leak in the system. I hope this isn't the case but it is a strong possibility — especially since I'm not totally confident with my double flaring skills. I did visually check for leakage wherever I had (and a few places I hadn't) worked cleaning off with brake parts cleaner, etc. Hadn't tried baby powder as suggested by Marbobj (Good idea; thanks.) Right now everything's wet from snow/rain so that won't work. The Brake fluid level has not dropped. Any other suggestions as to how to confirm if there is or is no leak?
   
   
3. So, I'm leaning toward thinking maybe I simply haven't bled the system thoroughly enough —which, I guess, is good news. I could just bleed them again and keep bleeding them 'til the cows come home (or til I've run through a few gallons of brake fluid, whichever comes first) but, I think, only after I've positively confirmed that the system is closed, no?
   
   If I'm bleeding them incorrectly, how do most of you determine when to stop bleeding each wheel? when you're seeing no more bubbles in the tube, once you've accumulated a certain amount of fluid in the catcher bottle or only once you begin to get resistance pedal?
   
   I've been using different methods that recommend a different order. Can the bleeding sequence have significant impact on the success of the bleed?

(By the way, no anti-lock brakes.)

 

just to be sure:

you did have a good pedal prior to starting all of this, right?

 

I had the same problem with an old '74 Mustang II after replacing the front pads, then calipers and re-bled, re-bled and re-bled until I wanted to finaly push it off a cliff if I was near one.
I finaly discovered my front brake hoses to the calipers were bad but not leaking fluid only sucking air preventing me from getting any pedal.

After I replaced the hoses and........VIOLA!
I suddenly had pedal and was able to purge all the air out.
But it never leaked fluid so I couldn't track were it was bad.
I just deduced it was the hoses and got lucky.
At that time the car was only 12 years old but had been sitting under a pine tree for 5 years.

Good luck!

 

I once had a master cylinder problem that caused brake fluid to leak back inside the car at the break pedal. Feel around in the hole where the pedal shaft goes to the master cylinder to see if there is any brake fluid.

When your helper is letting up on the brake pedal you have the bleeder valve screwed closed, right.

Good luck.

 

Did you say "flaring"?,as in using a flaring tool flaring? If so, the absolute key to a good flare is to go easy on the tubing cutter, and that the cutting wheel is good. Go round and round and round with little turn-in each time, so you get a cut where you don't squish the tubing inward. Then you have to ream the inside of the tubing so that where the cut is is no thicker material than what the tubing is. Fat material at the cut only causes a flare to not flare good and have fissures.

 

Yes, even at the beginning when it was all together but with a ruptured line it had a good pedal.

Mackey, you're messing with my entire understanding of Fluid Dynamics and the basics of hydraulic systems! If it's sucking air in, how could it not also be squirting/leaking/oozing fluid out when pressurized? (Maybe just the first time then, after that, air both ways?)

Weather's not bad today and I'd like to be out there wrapping this up.. but I don't know exactly what I can do. Seems to me the pivotal issue is: is the system closed? I'm going to try the clean and powder approach first if I can.

Any other suggestions as to how to confirm if there is or is no leak?

 

yea, I know, it boggled my mind and it didn't make any sense but the fact was that one of the hoses was sucking air but not leaking fluid.........go figure.

I thought I knew it all till then.

 

The biggest problem is that you have no pressure at all. You worked only only on the back brakes and never touched the front brake system? If this is the case you shouldn't have lost the front brake pressure. The two systems, front and back are separate for safety reasons. You lose one, you still have the other, but this is simple logic.

If you have lost all pressure, front and rear and the reservoir for the front brakes was never left empty in the process of bleeding the brakes, then the master cylinder or its linkage would have to be suspect.

But why it would suddenly go bad, when it is relatively new and not having a history of recent problems would be odd.

Bleeding the brakes shouldn't require a great amount of fluid. You should be able to do it easily with ten ounces or less.

Keep us posted

 

Yessir, That's true, except bleeder screws and bleeding
That's what I thought but I wasn't certain. I can't say when it happened since, of course, I stopped driving the car after the rear line burst. However, I do have to admit that, whether it's due to a part failure, something I'm doing or my pumping assistant, the more bleeding we did, the worse it's gotten.

Is this true?
Even though it's usually recommended you bleed the rears first, if I go out tomorrow and bleed the fronts again using only the MityVac, if the master cylinder is OK, I should see some improvement in pedal resistance. (This should factor out two variables: a questionable patch and pumping assistant.) Is this true?

 

Yes, it's what you would call baseline true. If you have a problem in the front system - either air or assistant- and getting no pressure, you would make an improvement and restore some braking performance = pedal resistance.

The reason you do rear brakes first is to remove the most air down the longest travel of brake line first. The brake system of the front isn't restored to full braking performance until both systems are bled. Although they are isolated from each other as far as fluid reservoir they interact with each other through a pressure equalization valve.

In later model cars and ABS applications the function of that valve may be performed by another device or redesigned altogether.

I think you'll find the fix for the problem is fairly simple. However, looking into something more unique and complex, there was a case where the inner lining of a rubber brake line has become separated and, exercising theory, created a pocket of air that allowed the separation to act like an air bladder. In other words, you could not get the air out of that system with bleeding. It showed up when a caliper was being replaced, the fluid was out of the line and the air entered the separation. Once again it was theory, but fixing it involved changing the rubber line.

Hope this helps,

Bob

 

Here's the latest: Progress was made!

Something significant happened. What, exactly, and why, I'm not sure. Perhaps one of you can offer an explanation.

I bled the fronts again using the MityVac. I kept on repeatedly bleeding each side 'til I filled the bottle with fluid 1—1.5 times (about 16, or so, ounces).

Put it all back together, tested it and noticed a marked improvement! It went from virtually no pedal at all to some resistance; not great—I wouldn't want to drive around like that— but there was a definite improvement.

So while the weather was holding out, I had the tools out and my dirty clothes on and I was feeling inspired, I figured I'd do the rears again, as well. I put up the back end and bled the rear brakes exactly as I did the fronts (with MityVac repeatedly 'til I filled the bottle with fluid 1—1.5 times)...twice: LR, RR, LR, RR. I thought "with the recent improvement after bleeding the fronts, this has to make it even better!" So I put it all back together and tested it to find I once again had NO brakes! What the heck happened?

At that point I figured "That's it! I've got to take it to a real mechanic!" Hoping to drive it in, I put the front up again, repeated everything as before and once again got some brakes; perhaps even a bit better than before — almost acceptable.

I understand why the brakes improve after bleeding the front; that's what's supposed to happen but what's causing me to lose them again after bleeding the rear? Can anyone explain this?

 

Some of these things are hard to work on from a distance. However, the only place the two systems come together is at the master cylinder and the equalization valve (or proportioning valve). In the master cylinder you could conceivably transfer air from one to the other, but I've never seen that - if it did happen.

In the proportioning valve you have a distribution of pressure between the two systems (front and rear) and I can't see anything moving from one system to the other, unless something had completely come apart in the valve. Since you have an equalization of pressure, when you completely remove resistance from one system i.e. introducing air, you would lose some resistance from the other system to the extent of the travel of the valve. Then it would stop. You shouldn't lose everything.

 

O.k. I've been following this thread for a few days and nobody has mentioned the possibility of a "dual diagonal" system. meaning that one port in the master cylinder controls the left front and the right rear and the second port controls the right front and left rear. It's a possibility anyway so the next time you bleed them try this sequence
rr,lf,lr,rf. If that still doesn't do it you probably have a bad master cylinder.

 

That would help explain some of the odd things he's seeing. But I don't believe those systems came in until the late nineties or after the turn of the century.

 

stuck proportioning valve??

or at least sticking.

When he bled the front, he may have gotten the valve to reset, if not completely, at least to cause a change.

I can remember fighting a few vehicles with bad prop. valves that had me banging my head on a wall.

 

If I remember correctly; I've had to use that pattern on some of the mid or late 80's chryslers.

 

You're right on the Chrysler products. They are showing a diagonal configuration for the brakes. I've got a stack of manuals, but nothing for Action Claw's particular car.

I think the answer to the problem is something simple, but I not sure what it is.

 

In case this helps others with a similar problem in the future, what finally solved this was a new master cylinder. I wouldn't have thought this because

1. the master cylinder was OK before this started
2. master cylinder was already replaced only a year or so before

Our guess is that maybe we applied too much pressure and damaged it while bleeding.