Brakeline question

[Patcon]

Been there; done that! 😞

[AK260]

"OBVIOUS'ly CAPTAIN, I surely will  try not to forget it...It would be detrimental to the success of the project...Wasted time, effort, and material.
Thanks for the reminder.  It would suck to forget that part of it..

The clue is in his name! ;)

And yes we’ve all done something like that and kicked ourselves hard!!

[Captain Obvious]

3 hours ago, AK260 said:

we’ve all done something like that and kicked ourselves hard!!

Wait... Are you asking if I've done something just like that?

https://www.youtube.com/watch?v=VomBuudIDsM

[240z70]

Activities:  Front to back Brake Line replacement, Rear Handbrake cable replaced, Clutch Line replaced due to visible wear and tear, MC pressure retention valve, remove & replace speedometer cable.

MC Pressure retention valves were seen in both MC orifices.  The one servicing the disk brakes was removed.

Clutch Line Replacement: No problem, Adequately bled it afterwards.  Clutch functions well.

Rear Handbrake Cable: One heck of a job.  Because of dual exhaust, and drive shaft were in place, this is one *itch of task.  No room to maneuver.  However it got done.  May still need additional adjustment but for now it stops the car from rolling.  Also, the cable is longer on one side than the other.  Didn't know that.. Issues, one of the tabs securing the line to its holder in the tunnel broke, had to make one.  Will need to buy replacement ones but they are narrower than the brake holding tabs and not sure where to get these new.

Remove/Replace Speedometer Cable: R&R Speedometer cable.  You have to be a circus contortionist to work upside down under the dash....Got done.  When tested it was a bit jumpy/ delayed, but it did work.  Could be because of years of non-operation and that fault may be inside the gauge itself...The old cable was rusty and had broke in half.  The plastic/rubber outer casing was damaged and missing in some spots.

Front to Back line replacement:  Well, I actually did "OBVIOUSLY" forget, BUT the line was only flared on one side (back), since i cut it longer than needed because I want to place it first and then see how and where i would cut it....hah hah, before I attached it to the car.  So the fitting was fed on the hood side and I tied a rope behind it, then pulled on the rope while underneath the car and the fitting made its way all the way to the back...Pretty easily, actually.

Cut back the old line to the tunnel area so it would not be left in the engine compartment and leaving the securing tabs there free for the new line.Then I isolated the line, by getting two long pieces of fuel hose 5/16 or 3/8 and cutting it long ways in a spiral cut that would wrap around the line the entire length of the under-body.  Then I zip tied the hose every 6 inches around the line.  Did not cut the line on the back side, just bent it out of the way.

The next thing was to now secure the line/hose along its way and out of the way of any pinch points and/or moving parts.   Then the final touch was to bend and secure the line along the underside.  Looked good.

Now that left me free to bend and secure the new line into the brackets in the engine compartment that had held the old line.  Now came the time to put on the front fitting and bend the line accordingly to the MC.  Then I knew where to cut it and flared (once again ensuring that the fitting was on the line and facing the right way.  Then I flared it and could now connect it to the MC.

Bled all four wheels, and tested brakes:  The brakes do stop the car BUT take 3 times the distance.  The brake pedal does go all the way down and is soft, (feels almost like power ABS Brakes) not that traditional had mid way resistance.  Will have to analyze and address again.  I guess another way to put it is to compare it to the steering on a 240z compared to the powered steering on a new car.. 

Known:  The MC is a 15/16 which provides additional stopping power (~20%+) versus the stock 7/8 MC, and the Booster is a 7" double diaphragm which also provides additional stopping power (~27%).  Together, the added stopping power should make the car brake and curl on a dime.  It does not.

Suspected: The Booster reaction disk is missing, and the booster push rod is not correctly adjusted for length.  This would create a long brake push.  It does not have an airy mushy push like when a brake system has when it has air in the system, HOWEVER I did not bench bleed the MC and the fluid receptacle was empty.

Path forward:  Remove the MC, Remove the Booster, check for existence of reaction disk (if not there, buy/make one - 6mm thick I believe), Adjust booster push rod correctly, reinstall booster/MC, bleed MC.  May also re-bleed the 4-wheels.

Assistance:  Any and all would be appreciated in the form of diagnosis, suggestions, and information on perhaps where to get a reaction disc and what the soft brake causes could be. 

[grannyknot]

I've never had to fool around with the reaction disc but you can bleed the MC by routing some clear hose from the bleed screws on the MC and bring that hose up and immerse into the brake fluid reservoir then just pump the brake pedal until all the air bubbles are gone, without bleeding the air from the MC first you'll never get it out of the rest of the system.

[Tweeds]

I'm not an expert so take what I say with a grain of salt. That being said, I'd rebleed the brakes real careful like, as grannyknot said. Also, if you completely drained the master cyclinders before fitting the new lines, you may need to do a bench bleed. I don't really know what that entails as I've never done it, but I've read before that it's good form to do a bench bleed if you completely drain the cylinders, but it's especially applicable for new master cylinders. I completely drained my cylinders last time without a bench bleed and I turned out alright, though. If you're booster is failing, it should make the brake pedal stiffer, not softer (again, I'm no expert). Either way, you could block off the brake booster to isolate the problem to the brakes themselves - vice grip the brake booster's vacuum hose if you're not worried about potentially damaging it.

In short; if I had to guess, there's just air somewhere in the brake system. When you hear hoofbeats, think horses, not zebras. Fingers crossed you don't have to rebuild the booster! (PS: How'd the flaring tool treat you?)

[AK260]

I agree with grannyknot, when I read your post my first reaction was air in the system.

When I replaced all but one of my brake lines last year, I had this exact problem. It kept coming back too as there was the tiniest weep in two of the connections that simply needed tightening up a fraction more.

Use white kitchen towel / tissue to check the lowest point of each pipe to ensure you don’t have a tiny leak somewhere.

Lastly, I stopped using the pumping the fluid back into the reservoir method as I found it was introducing very small air bubbles back into the reservoir. These days I just pump it into another container.

Ps. I just discovered this tool at the weekend. If I did it again, I would buy one of these.

[Patcon]

I didn't see a source for one in the states

[240z70]

13 hours ago, Tweeds said:

(PS: How'd the flaring tool treat you?)

Tweeds,  hey what can I say? You were right on the money with that tool.  Simple to use, no issues.  Did not eve try the other type that I have since I did not want to waste time and definitely not waste line once I had it in place, isolated and secured....Thank you for the advice.

Also, thanks to all who have provided input which I will follow.  I will try to bleed the MC first, then I may just redo the wheels, and try again.  I will also check for leaks.

If I cant fix it, I will remove the booster and either make my own reaction disk if it is missing, redo the booster push rod adjustments or just plain replace the booster with a new one.  If I go with the adjustments, and it still does not work, that will be an automatic decision to buy and replace the booster.  If I don't feel like messing with the adjustments, then that will also be a decision to just replace the booster. 

Don't know yet how I will feel.  Getting tired of bleeding brakes to no avail....

https://www.jegs.com/i/JEGS/555/631011/10002/-1

 

Edited June 3, 2021 by 240z70
Typo

[240z70]

5 hours ago, Patcon said:

I didn't see a source for one in the states

Pat, could one just make one?  I mean, if you have a metal lathe you could turn a big chunk of aluminum (very expensive..) or just a block of hard wood such a oak, etc. and make it.

It should not be a problem if the wood is hard and can fend off damage from the pressure and it would be very cheap to make.  almost any size bend you want.  Add a bottom base and screw it onto your work bench when you need it.

The other idea I had was just buy (fleamarket/craigslist) some cheap V-Groove Belt pulley/wheels that have the same shaft hole size, grab a small steel plate, weld a shaft on it vertically, and put all your different sized V-Groove pulleys on the shaft.

Just make sure that the pulleys have the same center hole diameter size.  Or make multiple shafts, one say for larger pulleys and others for smaller tubing sizes.  That will let you do anything from small tube size up to whatever size you need.

There is not many sizes that one would need.  Anyway, just an idea of how to possibly do it on the cheap and easily accessible.  As my dad use to say " Be frugal, when you need something, make use of what you have first, then look for the easiest solution to adaptation to fulfill the need'.

[AK260]

Pat, could one just make one?  I mean, if you have a metal lathe you could turn a big chunk of aluminum (very expensive..) or just a block of hard wood such a oak, etc. and make it.
It should not be a problem if the wood is hard and can fend off damage from the pressure and it would be very cheap to make.  almost any size bend you want.  Add a bottom base and screw it onto your work bench when you need it.
The other idea I had was just buy (fleamarket/craigslist) some cheap V-Groove Belt pulley/wheels that have the same shaft hole size, grab a small steel plate, weld a shaft on it vertically, and put all your different sized V-Groove pulleys on the shaft.
Just make sure that the pulleys have the same center hole diameter size.  Or make multiple shafts, one say for larger pulleys and others for smaller tubing sizes.  That will let you do anything from small tube size up to whatever size you need.
There is not many sizes that one would need.  Anyway, just an idea of how to possibly do it on the cheap and easily accessible.  As my dad use to say " Be frugal, when you need something, make use of what you have first, then look for the easiest solution to adaptation to fulfill the need'.

I like the wood turning idea!!!

For mine I ended up using a selection of sockets, paint pots and pulleys. Not ideal as you could easily flatten the pipe on the bend not to mention hard work to make these shapes ...





@240z70 - good luck chap! Keep us posted!

[Tweeds]

Glad the tool worked for you! Consider yourself saved from a lot frustration, far too many cuss words, and several feet of wasted brake line! Makes it worth the extra $20-30 if you ask me.

Again, here's to hoping you don't have to rebuild/replace your old booster - brake fluid's way cheaper.