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Spongy Brakes

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K

Klepper

Senior Member
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So after I installed my water pump, I jumped in my Healey to go for a spin around the block. I pushed on the brake peddle and it went all the way to the floor /ubbthreads/images/graemlins/frown.gif. If I pump the peddle a few times, it goes nice and solid again and stays solid until I let off, so I know I have air.

I have bled the brakes a number of times on my Healey, and it has always been tough. I did a search on this forum on bleeding brakes, and it sounds like a common problem. I did see someone mention "gravity bleeding". Does anyone know what this means? Any other advice on bleeding? Which wheel do people start with?
 
Left rear, Right Rear, Right Front, Left Front. Do the longest lines first. I assume you dont have any leaks and that all rubber hoses are fresh. The pumping does suggest air in the hard lines. /ubbthreads/images/graemlins/confused.gif
 
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I did see someone mention "gravity bleeding". Does anyone know what this means?

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It means to open all of the bleeder screws & let fluid run out by gravity only. It usually takes a couple of hours & you have to constantly check the supply reservoir during the process.
D
 
Re: Gravity bleeding ... you can attach a long clear flexible tube to each bleeder screw and fix the open end of the tubes to something above the reservoir height (and away from the paint of the car). Then open the bleed screws and let gravity work the air bubbles out. As Dave says you watch the reservoir to make sure it stays topped up but once the tubes are filled you can leave this setup overnight (as long as it's not leaking around the bleed screws). I prefer to power bleed with an EZbleed or the like ... no patience for the overnight stuff!

Cheers,
John
 
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(as long as it's not leaking around the bleed screws).
John

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This seems to be a major problem when gravity bleeding or when "suction bleeding" through the bleed screws. The screw threads were never intended to be a seal. I find that taking the time to put a wrap of teflon tape around the screw threads pretty well solves the problem. Also prevents "frozen" screws.
D
 
[ QUOTE ]
[ QUOTE ]
(as long as it's not leaking around the bleed screws).
John

[/ QUOTE ]
This seems to be a major problem when gravity bleeding or when "suction bleeding" through the bleed screws. The screw threads were never intended to be a seal. I find that taking the time to put a wrap of teflon tape around the screw threads pretty well solves the problem. Also prevents "frozen" screws.
D

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Dave knows,

teflon tape and a mity vac. only way to go. makes even a spridget clutch slave a piece of cake

mark
 
I found thise method to be very effective, shown to me by a mechanic. With help from an assistant, tell him to give the pedal 2 quick punches and one long one on which he will hold. This pushes the air bubbles to the end. As he does the long one, open the bleed screw. when he gets to the end of this stroke, close it. do this about 3 - 5 times for each wheel and make sure the master remains filled. It takes me less than an hour and the pedals are nice and firm.
 
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With help from an assistant, tell him to give the pedal 2 quick punches and one long one on which he will hold. This pushes the air bubbles to the end. As he does the long one, open the bleed screw.

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I can't imagine how this would push the air bubbles anywhere with the bleed screw CLOSED. It would only compress the air in it's present location. You are right about the general procedure which works well in many cases. Just questioning the "pushing the air bubbles to the end"
D
 
I agree - something needs to make the air bubble move along through the pipes. Although I had the same question with the "gravity bleed" method. Why wouldn't the air bubbles stay trapped in some high spots (top of the loop of the flex hoses, for instance)?
 
Don't know, there certainly isn't fast enough flow to carry air out of the high spots. Also not sure if it would work on the more viscous silicone fluids. I've never had the patience to carry gravity bleeding to completion. The whole purpose of pump up & release is to create high enough velocity to sweep the air out of "high places". We must be missing something?
D
 
As explained to me, doing this accumulates the small bubbles into larger ones so they will be easier to get out from the system. You have a good point but when I had problems bleeding, he showed me this technique and it worked well.
 
[ QUOTE ]
With help from an assistant, tell him to give the pedal 2 quick punches and one long one on which he will hold. This pushes the air bubbles to the end. As he does the long one, open the bleed screw.

[/ QUOTE ]

I've heard and seen this used (on a MGB last month).
It goes against the grain of all the British repair manuals, which usually suggest to push down, open screw, close screw, release pedal, wait 10-20 seconds, etc
I have used the British method with varying results--on the Sprite slave, it never seems to work and I give up. By the next day, because of air bubbles or something, everything works fine.

I have been using the mity-vac, which is priced well at auto-zone.

When I have used a clear plastic tube into the 'jelly jar' it seems that the air bubble gets pushed along as the fluid is being pumped--the fluid doesn't seem to pass it by.
 
If brakes are still spongey after much bleeding, you may wish to:

Check brake drum adjustment.
Be sure that you are using the proper brake fluid (and do not mix silicon with regular fluid).
Bleed at a "high point". Have an assistant pump up pedal and hold. *Just* loosen line(s) going into master cylinder until some fluid (and hopefully some air) escape. This is messy and may ruin paint, so place rags under the master cylinder. Make sure that assistant does not release pedal until line is re-tightend.
 
Back in 1964 I had the same problem with my BN2--pedal to the floor( and sphincter in a knot) and furious pumping until it 'catches' and is fine(not spongy)--until the next time it goes to the floor. The total failure was not predictable and I found myself constantly checking the brakes while driving and actually slowing down a bit to ensure I would have enough time to pump if I needed to. Bleeding did not fix this problem at all. What worked was a master cylinder rebuilding. The pedal to the floor thing is OK only if you are an adrenalin junkie.
 
Thanks for all the responses! I decided that before I start bleeding, I would replace all three flex hoses. I "think" they are only about 4 years old, but that probably means they are 6 years old! The new ones are in the mail (along with 4 new bleed screws), and I will start bleeding when they arrive. Thanks agian!
 
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