Brake bleed - neverending?

redeye

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Hi All,
I just got done with my rear axle/rear end restoration on my 96 LC. In the process I replaced every brake line from the LSPV back, and replaced the LSPV itself. Rear calipers were not replaced, but cleaned up and reinstalled with new bleeders and dust covers.

I followed a few "brake bleeding" threads, and bled the brakes no less than 5 times in this sequence: PS rear, DS rear, PS front, DS front, LSPV last. No matter what we do, air bubbles are still coming out of the front bleeder valves. Not just a little, but a lot. Looks like beer foam. I wish it was beer. The day might've ended better.

Anyway, all the fluid comes out of each bleeder valve nice and clean now. But the brakes are SUPER spongy. I limped it home from my friend's garage (1.5 miles away) so I wouldn't overstay my welcome any more than I already had - it was in their shop for a month.

The sponginess won't get any better, although after the 5 time bleeding it did seem somewhat better, but still not above what I would call "too dangerous to drive". Did I not follow the correct bleeding sequence? I just read in another thread that I should've done PS rear, DS rear, LSPV, then move onto the fronts.
 
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Do you have any oily/brake Field under the dash above the brake peddle?

How are you bleeding? Pump until you get a solid peddle and hold while the other person opens and closes the bleeder before you move the brake peddle again? PS rear-DS rear-LSPV-PS front-DS front?
Always start at the farthest from the master cylinder to the closest when bleeding.

I'm sure you double checked all your new hoses and connections for any signs of oil around the connections?
Are your front calipers pulling any air at the seals?
 

redeye

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No fluid showing under brake pedal inside vehicle.

We opened the bleeder, pumped pedal till air bubbles were gone and fluid was clean, then shut bleeder. But for the fronts, we never saw air bubbles stop coming out, so at some point we just quit. The last couple times we bled, we placed a bucket with fluid underneath and kept the tube submerged in the fluid.

We weren't following the sequence you mentioned above. But I'll gladly do this again with the correct sequence above.

I double and triple checked all the connections. There are no leaks.

I'm not sure what you mean by "pulling air at the seals" for the front calipers.......
 

Kernal

 
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Last year I also had a heck of a time getting the air out of my system, then realized that my rear Speed Bleeder screws were not seating fully, just enough to let air in and a very small drip out. Swapped them out with new OEM bleed screws. Point is you might want to also double check that the tip of your bleed screws are clean, not rusted or damaged and seating properly; the conical tip will have a ring near the end where it seats into the caliper. If they aren't seating the ring or circle will not be complete. I also followed the sequence above; start with PS -> DS rear, then LSPV, and PS -> DS front last.
 
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Did you make your lines yourself? Did you double flare the ends? Sounds like you have a connection on your new segments that are letting air in. If you used any non-OEM lines or connectors, make sure they are double flare and inverted cone type connectors. The 40 sections has some pretty good writeups on brake line replacement.

Bryan
 

redeye

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I'm hoping it's just the sequence that messed me up. My bleeders all seem to be OK. The two on the rear calipers are brand new, so I know those are good. I didn't touch the front calipers at all while working on my rear axle project.

In any case, maybe I should clarify how to bleed properly. Here's how I did it, please correct me if this is incorrect: Person inside the truck did not press on pedal until I unscrewed bleeder and connected tubing. Then I asked them to press the pedal down several times until I saw clean non-bubbly fluid come out. Then I asked them to press it one more time to the floor and I closed the bleeder.

After re-reading the FSM it appears this might be wrong. Maybe I needed to:
1) first have the person inside the truck press the pedal a few times (to build pressure presumably),
2) then unscrew bleeder after they've pressed and held the pedal down,
3) wait for some fluid to start coming out,
4) at this point tighten bleeder,
5) unscrew again, wait for no bubbles, then
6) tighten bleeder.

Do I also need to bleed master cylinder? FWIW, I notice a clicking sound when depressing the brake pedal. I don't remember hearing that ever before.
 

Pin_Head

 
 
 
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You may be bleeding them ineffectively or the master cylinder is bad and sucking air on the back stroke. Here is the proper bleeding procedure:

Use the 2 person method:
Open the bleeder valve a half turn and yell "down".
Your friend/wife stomps hard on the pedal, yells "down" and holds it down.

The fluid should squirt 3 feet or more. If not, he is not stomping hard enough or you didn't open it wide enough. The turbulence from stomping on it gets out even the stickiest bubbles.
You close the bleeder and yell "up".
He lets the pedal up and yells up.
Repeat until you get a strong stream with no bubbles.

After about 8 pumps, you may need to refill the reservoir.
 

redeye

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Worded that way it makes sense. I'm going to try this again tomorrow and report back. This is the last part of the project - I can hardly wait to officially get it back on the road.
 

CycloSteve

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Stuck between a rock and a hard place
My two-person bleed method:

1. Person in rig pumps the pedal several times then holds the pedal down as hard as they can.
2. Person under rig THEN opens the bleeder and fluid goes into the capture bottle (use a small CLEAR hose so you can see the bubbles).
3. When no more fluid comes out (or slowly dripping), THEN close bleeder.
4. Repeat #1-3 until no more bubbles, move on to the next caliper.

Tips:

1. Always be sure that the master cylinder reservoir is full before the next bleed
2. 80 order is PS Rear, DS Rear, PS Front, DS Front, LSPV.
3. Do not use speed-bleeder valves as they do not fit the 80's well at all (based on several other posts)
4. The cheap one-man bleeders work just fine ($5-10 at your local parts house).
5. Sometimes tapping lightly with a hammer on the caliper can help to free any stuck bubbles.
6. You may have to repeat the bleed after a test drive, or a week later if any bubbles migrate through the system.

:cheers:

Steve
 

redeye

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Wow....I'm going nuts doing this. I've just done it again, but did LSPV before moving onto fronts. I'll do the above sequence since the last session proved ineffective. Pedal still drops all the way to floor while running back and forth in driveway.

Can someone confirm the vehicle is NOT running during this procedure? I've not done it while running. It seemed unsafe to do so.
 

Kernal

 
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I'm not the expert on this but IIRC some people have opened one of the lines on the top of the ABS unit to bleed any air that might be stuck in there. Also from reading multiple threads some say do not press the pedal all the way to the floor as you may damage a seal in the master cylinder?? Did mine with the engine off, don't recall anyone mentioning doing it while the engine is running.
 
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Wow....I'm going nuts doing this. I've just done it again, but did LSPV before moving onto fronts. I'll do the above sequence since the last session proved ineffective. Pedal still drops all the way to floor while running back and forth in driveway.

Can someone confirm the vehicle is NOT running during this procedure? I've not done it while running. It seemed unsafe to do so.
It sounds like your bleeding method is flawed. From what I understand you are pumping the pedal several times while the bleeder valve is open. This will result in air being sucked into the system on the backstroke of the pedal going up.

There was a post above that had great instructions (down, up communication). Try that method and report back.
 

redeye

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Kernal: I see a couple lines running into the ABS unit. Just undo one?

clandr1: You're correct. The first time we were doing this (yesterday) we were pumping while the bleeder was open and it was just sucking bubbles back into the calipers. Today we are pumping, holding pedal, open bleeder, wait for bubbles and fluid to stop coming out, close bleeder, let up on pedal and repeat.

Do I need to bleed master cylinder? From FSM it looks like I'd need to undo the two brake lines and hold my fingers over the holes and have an assistant press down pedal.
 

Pin_Head

 
 
 
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I would just bleed the calipers properly first and see if you get a firm pedal. Shut the bleeder screw when fluid is still coming out to be sure that no air gets sucked back in. If not, then you can worry if a bubble is hiding in the ABS or a bad master cylinder. Brake fluid is cheap.
 

Kernal

 
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I'd wait for confirmation about the ABS; I never cracked the lines going into my ABS unit, just recall reading where someone had done so in the past. When I bled my system last year it took many tries until I got the one man bleeder bottle, that made quick work of it. The advantage to the one man/one way bottle is that once it is hooked up to the bleed screw you can pump the brake pedal a few times with the bleed screw open as the bottle will not allow air to get sucked back into the system. Also, as best as I can remember the sequence I used that got the last bit of air out was as I listed above; the rear PS then rear DS, then the LSPV (I may have repeated this rear sequence twice), then the front PS and the DS front caliper last. When I did the front DS caliper last I got bubbles and a firm pedal. Worked for me.
 

redeye

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I just don't know. Went thru it again, doing LSPV last. We went until no more bubbles were coming out, but the pedal still drops right to the floor when I start the truck and move it back and forth in the driveway. No improvement.

I'm going to follow the FSM and bleed the master cylinder. There's a chance the reservoir was empty before we started bleeding yesterday.

If this doesn't work I'll just drink myself into a stupor and cry myself to sleep. ;)
 
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Do you have a source of compressed air?

A vacuum bleeder will save a lot of frustration. This is what we use around the shop.

Note that we never allow a system to fully run dry, this can create havoc in the ABS system, etc. If the system was run dry you should bleed at the brake master first. Follow the 2-man procedure below, of course, omit the tubing & bottle. Instead, use several rags to catch the fluid because it will damage paint.



When we do the 2-person bleed, we do the following:

WEAR SAFETY GOGGLES. BRAKE FLUID IN THE EYE REALLY HURTS.
1. helper pumps the brakes 3-5x quickly then HOLD the pedal down HARD
2. tech opens the bleeder valve (with clear hose into bottle) until fluid flows, then close
3. repeat until no bubbles.

If you are having air in one end of the truck (in your case: fronts only) then you can bleed the fronts only until you have some pedal feel.

If you suspect air in the ABS system, you can bleed the lines at the ABS pump as well. Also, you could actuate the ABS (put 2 tires on a gravel shoulder and hit the brakes hard) to cycle any air out of the system after you've got your brakes working properly. Repeat with the other side. Obviously don't do this on a road with traffic (!)
 
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Two person brake bleeding steps.

Start with a full master cylinder.

One person pumps until you get a solid pedal and holds the brake pedal down.
The other person opens the PS rear bleeder :wrench: (as they do the brake pedal will drop to the floor DON'T MOVE THE BRAKE PEDAL) then close the bleeder. The person in the car than pumps until they get a a hard pedal again. Repeat until you have no air and only fluid coming out.

Next check your master cylinder for fluid than bleed the rest as follows DS rear---LSPV---PS front---DS front. Always check the master cylinder for fluid after each bleeder valve before the next.

If you move the brake pedal while bleeding you are pulling air back in the system.
 
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