Later model brake bleeding

[WALTER]

Today was a great day. I drove my Spite for the first time after owning it for 5 years. I bought it in pieces missing many parts. Very exiting! I really appreciate all the great advice I've received from you all over the years. Thank you.
My current problem is the brakes. I upgraded to the split system. It leaked at the brake failure plug so I ordered a new one. The one I received was the wrong shape so I replaced it with a bolt temporarily. Could that be why it is so difficult to bleed? If the piston is designed to block off the side that has failed could it be sliding back and forth without the switch in it. And doesn't bleeding simulate a blown out cylinder?

Thanks,
Walter

 

[jhorton3]

Walter-congrats on getting the car back on the road! I know how you feel getting it back together from pieces. How are you going about bleeding the system? Are you getting fluid out where you're bleeding? I usually start with the most far away wheel from the master cylinder in terms of brake line distance.

 

[jlaird]

Yes, longest to shortest.

Like right rear, left rear, left front, right front.

 

[WALTER]

Standard longest to shortest. But I wonder if not having the switch in place may be allowing the piston in the 5-way splitter to slid around causing trouble.

Walter

 

[JPSmit]

shouldn't - as long as it isn't threaded deeper than the switch. when I bled mine, after a long time, it took longer than I thought and was harder than I thought. (in part I suspect because the only part I didn't clean out thorougly was the splitter.

That being said, one thing that me hugely was bleeding the brake to the splitter first. In other words, we disconnected the lines at the splitter (one at a time) - pushed till the fluid came through then reconnected that line and pushed the fluid the rest of the way through.

BTW I used DOT 5 so it wasn't as much a worry if it dripped. The paint is still intact.

 

[WALTER]

To quarts and still no good. It's making me crazier! I guess I should have bench bled the master. Didn't realize it was that important. I've tried both ways of bleeding. There is a bubble hiding somewhere. Arg.

w

 

[JPSmit]

what are you using at the end of the bleeding nipple? Lots here use speedbleeders etc. My friend made me a jar with tubing that fit over the nipple so that when the fluid came out -if anything got sucked back in it was fluid not air. then (2 person job) push - hold/ push-hold. Also, make sure your emergency brake is off - don't ask me how I know.

if you have pushed 2 quarts through, you either have a leak or you are letting air back in somehow. If you had a blockage it wouldn't let you use that much fluid. The system takes more fluid than you would think but I don't think 2 quarts

 

[WALTER]

The e-brake may have been on. I have standard nipples(well my brakes do). I did wrap the threads with teflon tape the last go around. Is it possible with too much pumping on the Mityvac it could suck air through the rear cylinders? If there was a leak it should leak fluid when under pressure.

w

 

[JPSmit]

are you using a Mityvac? - if so, I hope others will wade in as I haven't used one.

but I could imagine you sucking air in because the system is not that complicated.

forgive me assuming but when we did mine,

we filled the reservoir and pushed till fluid came out of each end of the splitter (one at a time because it seemed too slow there)

with the lines hooked up, my friend went to each wheel in turn with a box end wrench and his hose apparatus. He put the box end on the nut (on the nipple) and then the hose from the end of the nipple to the bottle.

I pushed the brake pedal as he opened the nipple and as I held the brake down he closed the nipple so that when I let go it drew fluid into the system. we just repeated till the brakes got hard.

I can't imagine what else it could be than air because you are right it would leak under pressure or if it were a blockage it wouldn't flow at all

keep us posted

 

[WALTER]

"I pushed the brake pedal as he opened the nipple and as I held the brake down he closed the nipple so that when I let go it drew fluid into the system. we just repeated till the brakes got hard"

That's how I expected it to go. Giving it another shot today. Using the above method and mityvac method.

Thanks
Walter

 

[Billm]

My opinion (you know how that goes...) is that you are causing the shuttle to move as you are bleeding, and this might be messing you up. The shuttle moves from the high pressure side to the low pressure side and whichever side you are bleeding is the low pressure side so the shuttle could be shutting you off as you try to bleed and it doesn't "spring-return" at all if I recall correctly.
The only option is to verify that the shuttle is centered and then either bleed it VERY slowly with extremely low peddle pressure OR use something like a "mini-vac" bleeder (very low pressure differential) and do it that way.
Good luck
Bill

 

[WALTER]

Bill, I think your opinion is a good one. I read in one of my manuals that the shuttle can be centered by having someone monitor the brake failure light while bleeding. Working it back and forth slowly till the light stays off. I have to get the proper switch before I can do that. I've gotten to the point of not being able to push the peddle to the floor. I think I was pulling air through the rear cylinders. If I am pulling brake fluid with a strong vacuum through a nipple it would cause the shuttle to close down causing more restriction making it easer to pull air through a seal. Even the one on the other side of the car. That could be a draw back of the Mityvac (no pun intended) on this situation. I think there may be light at the end of the tunnel.

Walter

 

[JPSmit]

how's it going?

 

[WALTER]

I suppose it's going nowhere till I get the switch that will help hold the shuttle in place and center it. Thanks for the help. I'll keep you posted.

Walter

 

[SilentUnicorn]

I suppose it's going nowhere till I get the switch that will help hold the shuttle in place and center it. Thanks for the help. I'll keep you posted.

Walter

Walter,
the switch will not hold the shuttle in place in the PWDA (pressure warning differential assembly)..or something like that. The springs inside the assembly will do that. the switch is a normally closed type and when installed will be held open by the shuttle. If something happens to the front or rear system the shuttle will move to the low pressure side, when the pedal is depressed and the switch will drop into a groove turned into the shuttle and activate the warning light.

Definitely bench bleed the master. At this point you most likely have fluid in the system and should not have to worry about the PWDA. If you like take the bolt out and use a mirror to look in the hole and be sure it looks symmetrical. You should be able to see the shuttle. there are o-rings on the shuttle that prevent leakage from one side to the other or into the switch cavity. If you have fluid in the switch cavity it is time to replace the o-rings.

the mity-vac should work, but all the connections must be tight or you will just draw a mix of air and fluid, and get no where. Once you have drawn fluid thru the system, i like to usually go to the old pump and open the bleeder routine.

i hope i havent been to redundant in my description. good Luck

mark

 

[WALTER]

Hi Mark,
So what I hear you saying is that I need new O-rings instead of a new switch. Now for the big question. Do you know what size O-rings, so I can minimize the brake fluid dribbling in my freshly painted engine compartment? And, How does one remove the shuffle. I'm hoping you don't say hydraulic pleasure.

Thanks,
Walter

 

[SilentUnicorn]

If you have brake fluid in the switch cavity then the o-rings are leaking. the PWDA is easily rebuilt. there is a cap on the forward end that unscrews. place the assembly in a soft jawed vice and get a wrench on the endcap. you should be able to easily get the shuttle out. take care not to damage the bore. Is your brass or steel? Steel ones can corrode, brass ones are probaly better, but either way you don't want to have to buy a new one. basically there is the shuttle, and a spring on either end. the shuttle has 4 o-rings IIRC.

when i did mine i bought a bag of the o-rings, 50 i think, i will happily send you some if you pm me your addy.


mark

 

[WALTER]

Thanks Mark. I'm surprised you got o-rings to work. I actually found a diagram in the Haynes manual. It shows special seals on each end and says the copper washer should be renewed. Moss does have a repair kit for the Sprite failure switch (181-995).I think I'll just order it. My switch is brass so I'm thinking the cylinder should be good.

Walter