Easiest way to remove air from clutch cylinders and line
Background
We have been trying to bleed the clutch of my brother's Toyota Hiace 1999 for a week now (on our free times during the week). There was dripping. I removed the rubber cap but the inside of the cylinder was not wet, the drip was not from the piston rubber, it was from the outside. I removed the slave from the bolts and found the pipe loose. I realized the drip was not from the cylinder / piston but from the screw / link of the connecting pipe. It was not tight because my brother mis-screwed it in, so it was re-creating its own thread. Since it was already halfway in, I just force-screwed it in with a pipe wrench (because the hex screw had destroyed the bolt). Until it stopped dripping. This took the longest because of lack of space.
So my dad and I were trying to bleed the clutch after the drip was gone. We've done this to many of our older vehicles, but this one just didn't work out.
So I went and read in the internet, trying to visualize where the air pockets might be hiding. Also considering other ways of bleeding: reverse bleeding, vacuuming, quick filling, but these needed more equipment.
Problems & Solutions
The first problem was that the master was oriented in such a way that the end of the cylinder was higher than the feedpoint. That means that air would naturally stay there when the fluid dries out, and even when it comes in. Additionally, the piping went over the master cylinder, meaning more prone to air pockets. Then it went down to under the vehicle. Another possible problem was that the slave had the bleed downward. I was thinking, if you want to take out the air from the slave, the bleed bolt must be the highest hole in the slave cylinder.
So I discussed with my brother what I thought was happening. And thought that maybe if I fully extrude and fully intrude the slave, the air pockets might exit from the top. Reasoning that air is nearer from the top than from the bottom. Also, maybe the reason why normal bleeding needs hundreds of pumps was that they are trying to make the air from the top exit from the bottom. But this case had too much air because even fully pumping the pedal didn't even make the slave move a little, when it was mounted against the clutch "seesaw".
So I removed the slave from the bell bolts and told my brother to pump. The slave cylinder slowly began to come out. When it was almost out, I told him to stop. I then pushed the cylinder while opening the bleed nozzle, and positioning the slave so that the bleed nozzle was higher than the rest of the cylinder, to try to get rid of the air in the slave. Did this about twice. When totally intruding the piston it was coming back out a little because of the spring. So I made sure the second time I did it, that the bleed nozzle was closed before letting the piston move out caused by the spring. Then I tried to ask him to pump again, and I tried to contradict his pumping. I felt the air was cushoning the effort. So I let the piston almost come out of the slave and then asked my brother to release the pedal (tank open position), meaning if I push in the slave piston all the displaced fluid would go back to the tank. And that's what happened. Additionally, I also tried to ask him to pump again to fill the slave, then asked him to keep the pedal on the floor, and I tried to push, initially it pushed, but on later tries, it didn't! Meaning that the master's rubber was actually blocking the fluid from going back into the master on that position. Good, it means the master is ok, it really is just the air. After several tries, having some confidence that the pumping would be slow enough for me to react before the piston totally comes out, I asked my brother to continue pumping, then when the piston was almost out, I tried to push it in w/o telling my brother to pump. With this, I found that sometimes, depending on the position of the master, I could make the fluid go back into the pump, but sometimes it wouldn't (on position down). I tried to play this about three times and noticed that the fight became solid. My brother also said that there was now some resistance. Obviously from my fighting the slave back. It seemed that this fullout-fullin-fullout-fullin action was pumping the air out into the tank above. We did it a few more times until it seemed as though there was no more improvement. My brother said that there was resistance on the bottom half but the top half was still airy. But I was too tired to continue pushing back the slave against the spring, against the master, and against the gravity.
Summary
In addition the known ways of bleeding: pumping 100-200 times, vacuuming, speed-filling, reverse bleeding; I would like to submit another method which might work more economically, less laboriously, and more intelligently. I just don't know how to call it. But the principle is to use the full excursion of the slave (w/c is about 5 times of the master) to pump the air to the tank (because it probably is nearer there).
We have been trying to bleed the clutch of my brother's Toyota Hiace 1999 for a week now (on our free times during the week). There was dripping. I removed the rubber cap but the inside of the cylinder was not wet, the drip was not from the piston rubber, it was from the outside. I removed the slave from the bolts and found the pipe loose. I realized the drip was not from the cylinder / piston but from the screw / link of the connecting pipe. It was not tight because my brother mis-screwed it in, so it was re-creating its own thread. Since it was already halfway in, I just force-screwed it in with a pipe wrench (because the hex screw had destroyed the bolt). Until it stopped dripping. This took the longest because of lack of space.
So my dad and I were trying to bleed the clutch after the drip was gone. We've done this to many of our older vehicles, but this one just didn't work out.
So I went and read in the internet, trying to visualize where the air pockets might be hiding. Also considering other ways of bleeding: reverse bleeding, vacuuming, quick filling, but these needed more equipment.
Problems & Solutions
The first problem was that the master was oriented in such a way that the end of the cylinder was higher than the feedpoint. That means that air would naturally stay there when the fluid dries out, and even when it comes in. Additionally, the piping went over the master cylinder, meaning more prone to air pockets. Then it went down to under the vehicle. Another possible problem was that the slave had the bleed downward. I was thinking, if you want to take out the air from the slave, the bleed bolt must be the highest hole in the slave cylinder.
So I discussed with my brother what I thought was happening. And thought that maybe if I fully extrude and fully intrude the slave, the air pockets might exit from the top. Reasoning that air is nearer from the top than from the bottom. Also, maybe the reason why normal bleeding needs hundreds of pumps was that they are trying to make the air from the top exit from the bottom. But this case had too much air because even fully pumping the pedal didn't even make the slave move a little, when it was mounted against the clutch "seesaw".
So I removed the slave from the bell bolts and told my brother to pump. The slave cylinder slowly began to come out. When it was almost out, I told him to stop. I then pushed the cylinder while opening the bleed nozzle, and positioning the slave so that the bleed nozzle was higher than the rest of the cylinder, to try to get rid of the air in the slave. Did this about twice. When totally intruding the piston it was coming back out a little because of the spring. So I made sure the second time I did it, that the bleed nozzle was closed before letting the piston move out caused by the spring. Then I tried to ask him to pump again, and I tried to contradict his pumping. I felt the air was cushoning the effort. So I let the piston almost come out of the slave and then asked my brother to release the pedal (tank open position), meaning if I push in the slave piston all the displaced fluid would go back to the tank. And that's what happened. Additionally, I also tried to ask him to pump again to fill the slave, then asked him to keep the pedal on the floor, and I tried to push, initially it pushed, but on later tries, it didn't! Meaning that the master's rubber was actually blocking the fluid from going back into the master on that position. Good, it means the master is ok, it really is just the air. After several tries, having some confidence that the pumping would be slow enough for me to react before the piston totally comes out, I asked my brother to continue pumping, then when the piston was almost out, I tried to push it in w/o telling my brother to pump. With this, I found that sometimes, depending on the position of the master, I could make the fluid go back into the pump, but sometimes it wouldn't (on position down). I tried to play this about three times and noticed that the fight became solid. My brother also said that there was now some resistance. Obviously from my fighting the slave back. It seemed that this fullout-fullin-fullout-fullin action was pumping the air out into the tank above. We did it a few more times until it seemed as though there was no more improvement. My brother said that there was resistance on the bottom half but the top half was still airy. But I was too tired to continue pushing back the slave against the spring, against the master, and against the gravity.
Summary
In addition the known ways of bleeding: pumping 100-200 times, vacuuming, speed-filling, reverse bleeding; I would like to submit another method which might work more economically, less laboriously, and more intelligently. I just don't know how to call it. But the principle is to use the full excursion of the slave (w/c is about 5 times of the master) to pump the air to the tank (because it probably is nearer there).
