Brake Bleeding (still have to pump brakes)
Created by: Morninglightmountain
Orig. Posting Date | User Name | Edit Date |
Jul 16, 2020 12:49PM | tsumini | |
Jul 16, 2020 07:26AM | Rosebud | |
Jul 16, 2020 12:46AM | Alex | |
Jul 15, 2020 05:52PM | h_lankford | |
Jul 15, 2020 10:40AM | MisterCinders | |
Jul 14, 2020 05:38AM | onetim | Edited: Jul 14, 2020 08:06AM |
Jul 14, 2020 05:28AM | CooperTune | |
Jul 13, 2020 08:48PM | tsumini | |
Jul 13, 2020 06:33PM | Rosebud | |
Jul 13, 2020 05:34PM | 6464 | Edited: Jul 16, 2020 03:46AM |
Jul 13, 2020 08:48AM | Rosebud | |
Jul 13, 2020 05:21AM | Dan Moffet | |
Jul 12, 2020 06:23PM | Morninglightmountain | |
Jul 12, 2020 05:43PM | malsal | |
Jul 12, 2020 04:27PM | dklawson | |
Jul 12, 2020 01:01PM | onetim | |
Jul 12, 2020 12:53PM | Morninglightmountain | |
Jul 12, 2020 12:12PM | jedduh01 | Edited: Jul 12, 2020 12:13PM |
Jul 12, 2020 10:13AM | Morninglightmountain | Edited: Jul 12, 2020 10:23AM |
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If you have to double pump the wheel cylinder are not adjusted correctly. I adjusted mine to a slight drag. First time out they dragged enough to get really hot. Cooled off and released but didn't back them off. Both front and rear did this.never backed them off. After cooling never had the dragging problem and still had a hard pedal. These are single LE drums and always a hard pedal. i would redo the brakes if I needed to pump them. I have 1 and 1/2 inches of pedal travel before hard pedal that takes up any lost motion of the pin wear and wheel cylinder movement before engagement.
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Quote:
Originally Posted by Alex
When I spoke the engineers at AP Caparro while chasing down the braking issue on Gertie, they were amazed that Mini brakes bled at all the way the outlet come up so far.
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Wheel cylinder diameter - what do you have fitted ?
The .700" brake MC doesn't really move enough fluid for .750" rear wheel cylinders and S discs up front. It'll work, and work fine, but you can end up with a funny feeling brake pedal that the slow-fill valve in the MC will allow to go away with a double pump.
If you've replaced the line coming out of the MC at the front at any point, make sure the u-bend is as low as possible to the outlet. When I spoke the engineers at AP Caparro while chasing down the braking issue on Gertie, they were amazed that Mini brakes bled at all the way the outlet come up so far.
The .700" brake MC doesn't really move enough fluid for .750" rear wheel cylinders and S discs up front. It'll work, and work fine, but you can end up with a funny feeling brake pedal that the slow-fill valve in the MC will allow to go away with a double pump.
If you've replaced the line coming out of the MC at the front at any point, make sure the u-bend is as low as possible to the outlet. When I spoke the engineers at AP Caparro while chasing down the braking issue on Gertie, they were amazed that Mini brakes bled at all the way the outlet come up so far.
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I never understood how gravity bleeding could work.
Engineering tells us that you need a velocity of 10 ft/sec to clear bubbles out of a water-density fluid in a pipe. This does not mean just opening the brake bleeder valve a bit. It means opening it wide with plenty of pressure behind it to shoot a good volume of fluid out like a jackrabbit. And not just for a split second. Think about the length of the brake lines and hoses and brake cylinders that need to be purged.
Do it, um, hard and long.
Engineering tells us that you need a velocity of 10 ft/sec to clear bubbles out of a water-density fluid in a pipe. This does not mean just opening the brake bleeder valve a bit. It means opening it wide with plenty of pressure behind it to shoot a good volume of fluid out like a jackrabbit. And not just for a split second. Think about the length of the brake lines and hoses and brake cylinders that need to be purged.
Do it, um, hard and long.
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Another way to gain brake pressure is to take the top off the MC and use something to keep the brake pedal pressed (like a spreader or short piece of lumber), then leave it for a few hours or overnight. This keeps the lines under pressure and allows the tiny air bubbles to make their way back up to the master. When you remove the brace from the pedal, you may find some addei e pressure.
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Quote:
Originally Posted by Rosebud
Quote:
Originally Posted by 6464
…a hose should be connected the the bleed nipple and go into a jar and the reservoir cap should be off or just placed on the reservoir.
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I do a lot of complete brake jobs and upgrades. I like to replace as much hard pipe as possible. Also all flex
hose, master cyl., wheel cyls., shoes, springs, adjusters, drums, disc and calipers or pistons and kits.
Working by myself brake bleeding can be a problem. I always start with gravity (and I do attach PVC hose
to my bleed nipples ) as well as a little brake grease to each bleed nipple thread. I have a vacuum pump but
but find in not that helpful. I also have a power bleeder which can make the biggest mess in no time. It seem
old school three pumps and hold works best for me. I find it best to pump slowly and firmly. My thoughts
are quick shape pumps tend to close the bias valve at the rear sub. Seems every time I have that needs a
pump to get a real pedal the rear gives up a small bubble half an inch long.
I may have set a worlds record for brake bleeding. We spent 30 hours and 5 qts of brake fluid. bypassed
a new remote brake booster and had full pedal in five pumps. Steve (CTR)
hose, master cyl., wheel cyls., shoes, springs, adjusters, drums, disc and calipers or pistons and kits.
Working by myself brake bleeding can be a problem. I always start with gravity (and I do attach PVC hose
to my bleed nipples ) as well as a little brake grease to each bleed nipple thread. I have a vacuum pump but
but find in not that helpful. I also have a power bleeder which can make the biggest mess in no time. It seem
old school three pumps and hold works best for me. I find it best to pump slowly and firmly. My thoughts
are quick shape pumps tend to close the bias valve at the rear sub. Seems every time I have that needs a
pump to get a real pedal the rear gives up a small bubble half an inch long.
I may have set a worlds record for brake bleeding. We spent 30 hours and 5 qts of brake fluid. bypassed
a new remote brake booster and had full pedal in five pumps. Steve (CTR)
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I too believe that there is probably an air bubble in the line. When I did mine I observed that the arch above the MC is a very good place to lose a bubble of air. I had spent countless times helping my son bleed his race car brakes. No softness allowed there. He had a tee in every line that was at the apex (highest elevation of each line). Usually it was a AN fitting so that simply pressurizing the line could be bled by loosening the fitting. I wouldn't suggest installing a fitting at the top of arch but it would make elimination of a bubble much easier if there was one there.
So i suggest the following method of driving the bubble out the front wheel bleed.
I guesstimated the volume of brake fluid between the MC and nearest front brake bleed screw and guesstimated the volume of a stroke of the MC. I guesstimated almost two stokes equivalent volume.
Then I fitted a hose to the bleed and immersed it in a container and (since I was alone) opened the bleed. Then using firm and rapid strokes(not furious) apply not less than three strokes without closing the bleed (keep reservoir full). When done close the bleed and check brakes.
Normal bleeding open/close/open/close..... allows the bubble to travel back up to the arch. You can bleed this way all day long and not move a bubble. It does use quite a bit of brake fluid.
If all else fails try this.
So i suggest the following method of driving the bubble out the front wheel bleed.
I guesstimated the volume of brake fluid between the MC and nearest front brake bleed screw and guesstimated the volume of a stroke of the MC. I guesstimated almost two stokes equivalent volume.
Then I fitted a hose to the bleed and immersed it in a container and (since I was alone) opened the bleed. Then using firm and rapid strokes(not furious) apply not less than three strokes without closing the bleed (keep reservoir full). When done close the bleed and check brakes.
Normal bleeding open/close/open/close..... allows the bubble to travel back up to the arch. You can bleed this way all day long and not move a bubble. It does use quite a bit of brake fluid.
If all else fails try this.
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Quote:
Originally Posted by 6464
…a hose should be connected the the bleed nipple and go into a jar and the reservoir cap should be off or just placed on the reservoir.
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Gravity bleeding. This method works well. Rosebud, A few details you left out. A hose should be connected from the bleed nipple and go into a jar and the reservoir cap should be off or just placed on the reservoir. If you use this method and still need a single pump, you probably need a master cylinder or a rebuild.
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As others have mentioned and based on the symptoms you describe, I'd say you have some trapped air lurking in the system somewhere. Besides the 2-man and EZ-bleed (vacuum) methods, there is a 3rd method that you might try. It's sometimes called the "restoration or gravity method."
Starting with the wheel cylinder furthest from the master cylinder, place a container under the bleeder valve and open the valve allowing fluid to drip into the container by gravity only and without any pumping of the brake. Obviously, the fluid isn't going to gush from the valve, it's simply going to slowly drip. This method may take an entire day for each wheel. As with all methods, take care not to allow the master cylinder reservoir to run dry and suck air. I usually check the rate of flow before I walk away so I have an idea of how frequently I need to top off the reservoir. It's usually not more than once per day.
Restoration shops often use this method when the master cylinder is questionable and they don't want to cycle the master past its normal operating range, as is the case when you push the brake pedal to the floor. I've occasionally had success with this method when all else failed.
Good luck and let us know when and how you resolved the problem.
Starting with the wheel cylinder furthest from the master cylinder, place a container under the bleeder valve and open the valve allowing fluid to drip into the container by gravity only and without any pumping of the brake. Obviously, the fluid isn't going to gush from the valve, it's simply going to slowly drip. This method may take an entire day for each wheel. As with all methods, take care not to allow the master cylinder reservoir to run dry and suck air. I usually check the rate of flow before I walk away so I have an idea of how frequently I need to top off the reservoir. It's usually not more than once per day.
Restoration shops often use this method when the master cylinder is questionable and they don't want to cycle the master past its normal operating range, as is the case when you push the brake pedal to the floor. I've occasionally had success with this method when all else failed.
Good luck and let us know when and how you resolved the problem.
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Once you get the bleeding and adjustment optimized, have a look at the amount of free-play in the brake pedal. The pivot and the clevis pin to the master cylinder shaft may be worn.
.
"Hang on a minute lads....I've got a great idea."
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The brakes worked slightly better after the cylinder change. Then worked a bit better after the rear shoe adjustments. The pedal still goes a bit farther than i'd like (not as far as before) and feels great after the first pump. I will tighten the shoes a little more to get a touch of drag. And re-bleed the brakes on the slanted part of my driveway. Busy week but hope to get it done by the weekend and I'll report back.
Thanks again guys!
Thanks again guys!
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Quote:
Originally Posted by Morninglightmountain
Good info, thanKs!
I'll try another bleed.
I'll try another bleed.
It also helps the bleeding if you can get the rear as high as possible.
If in doubt, flat out. Colin Mc Rae MBE 1968-2007.
Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.
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Quote:
Originally Posted by Morninglightmountain
I replace one rear brake cylinder I thought might be seized.
I adjusted both rear drums to where they'd barely drag then I backed them off half a turn.
I adjusted both rear drums to where they'd barely drag then I backed them off half a turn.
Did the need to pump the pedal get worse after you replaced the wheel cylinder?
Leave the brakes adjusted where they have a bit of drag. The wheels should not "free wheel" when an elevated wheel is turned by hand. They should make a bit of dragging noise and stop spinning within about 1 revolution.
Doug L.
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There are masters for use with disc brakes, and ones for drums around, also different size rear wheel cylinders for disc . It’s possible you have a mis matched set of components. Old flex lines can cause problems too. A good and proper bleeding is critical.
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Good info, thanKs!
I'll try another bleed.
I'll try another bleed.
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I always get the best bleeds with 2 people... One pedal one wrench opening closing.
I can get 1 person bleeds but like you find a bit of a double pump and the brakes feel better when using.
I recently had a drum brake car with the same symptoms... Did a double person bleed 1000% better
Slightly dragging adjusters Just fine. No Parking brake applied.
______________________________
You can read of many variations of to start closest to the Master or Farthest from the master.. I have done all ways.. Front first then rear etc... Rear far side vs rear near side etc.
Have your assistant apply pedal pressure , Crack the bleeder, let the pedal to to the floor. Close bleeder.
Do that 3x on each wheel - Just a procedure suggestion if you havn't already.
Goodluck.
I can get 1 person bleeds but like you find a bit of a double pump and the brakes feel better when using.
I recently had a drum brake car with the same symptoms... Did a double person bleed 1000% better
Slightly dragging adjusters Just fine. No Parking brake applied.
______________________________
You can read of many variations of to start closest to the Master or Farthest from the master.. I have done all ways.. Front first then rear etc... Rear far side vs rear near side etc.
Have your assistant apply pedal pressure , Crack the bleeder, let the pedal to to the floor. Close bleeder.
Do that 3x on each wheel - Just a procedure suggestion if you havn't already.
Goodluck.
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Hi Fellas,
1965 mini cooper
Front discs
Read drums
Since I've owned the car I've always had to give the brake a little pump before the brakes stiffen up and stop well.
Today I replace one rear brake cylinder I thought might be seized. I went around the car and bled all four corners. After that didn't improve my one pump situation I adjusted both rear drums to where they'd barely drag then I backed them off half a turn. It did improve a bit, but the brakes always stop much better after a pre-pump. Any thoughts?
Thanks,
S
also, I replaced the master cylinder a few years ago, but I suppose it could be faulty.
1965 mini cooper
Front discs
Read drums
Since I've owned the car I've always had to give the brake a little pump before the brakes stiffen up and stop well.
Today I replace one rear brake cylinder I thought might be seized. I went around the car and bled all four corners. After that didn't improve my one pump situation I adjusted both rear drums to where they'd barely drag then I backed them off half a turn. It did improve a bit, but the brakes always stop much better after a pre-pump. Any thoughts?
Thanks,
S
also, I replaced the master cylinder a few years ago, but I suppose it could be faulty.