Mxgrds
True Classic
With a new crunch between 1 and 2 I was worried that the clutch was not bled well enough after a revision of the pedal box. So i started to bleed it over and over again, but without results. It might as well be the synchromesh. But it made me think about the clutch dynamics. On the forum there are many ways how to bleed described. I was wondering were the air sits that is so difficult to get rid off.
Below a schematic of the clutch.
From left to right:
- reservoir
- supply line
- master
- pressure line
- slave
Master?
The pressure line exits in the middle of the cylinder. Some air might get trapped above that exit. If the valve reaches the end totally, the air will be pumped in the pressure line when bleeding. But does the valve completely empty the cylinder when the pedal hits the floor?
Pressure line?
Directly when the pressure line exits the master it rises 5 cm to pass the pedal box. Then it falls 30 cm to the midconsol. Then 150 cm to the rear and up 30 cm to the slave (approx).
The highest point in this line is, it think, the most likely part where air gets trapped.
Slave?
By manually pushing the valve into the slave completely, the air can be pressed out through the bleed nipple.
How to bleed then?
2 person job. One pumping the peddle and the other one operating the bleed nipple and a lot of shouting. Tried that but not always with success. A problem is the small reservoir. 3 to 4 times pumping and it needs to be refilled. Air that is just moved down in the pressure line is moving up again while the reservoir is filled. The pressure line has a large capacity, so with every pump the oil moves with the air bubble only a limited distance. In the 30 cm down and the 150 cm horizontally, the air will even rise between 2 pumps. To overcome this problem I bought 4 meter transparant silicon hose to pump the oil round fom nipple back to reservoir. Works great. You can pump 15 minutes without stopping and at the same time watching air passing by. Can be done by one person.
Still no improvement. Might be as well the synchromesh.
Bleed reverse?
Many people on this forum are very possitive of reversed bleeding. Why is that a more successfull method? probably because the trapped air in the highest point of the pressure line only needs to go 5cm down to get to the master and out in the supply line. And maybe the oil volume used is bigger. This is my last resort of hope to avoid a gearbox overhaul.
Below a schematic of the clutch.
From left to right:
- reservoir
- supply line
- master
- pressure line
- slave
Master?
The pressure line exits in the middle of the cylinder. Some air might get trapped above that exit. If the valve reaches the end totally, the air will be pumped in the pressure line when bleeding. But does the valve completely empty the cylinder when the pedal hits the floor?
Pressure line?
Directly when the pressure line exits the master it rises 5 cm to pass the pedal box. Then it falls 30 cm to the midconsol. Then 150 cm to the rear and up 30 cm to the slave (approx).
The highest point in this line is, it think, the most likely part where air gets trapped.
Slave?
By manually pushing the valve into the slave completely, the air can be pressed out through the bleed nipple.
How to bleed then?
2 person job. One pumping the peddle and the other one operating the bleed nipple and a lot of shouting. Tried that but not always with success. A problem is the small reservoir. 3 to 4 times pumping and it needs to be refilled. Air that is just moved down in the pressure line is moving up again while the reservoir is filled. The pressure line has a large capacity, so with every pump the oil moves with the air bubble only a limited distance. In the 30 cm down and the 150 cm horizontally, the air will even rise between 2 pumps. To overcome this problem I bought 4 meter transparant silicon hose to pump the oil round fom nipple back to reservoir. Works great. You can pump 15 minutes without stopping and at the same time watching air passing by. Can be done by one person.
Still no improvement. Might be as well the synchromesh.
Bleed reverse?
Many people on this forum are very possitive of reversed bleeding. Why is that a more successfull method? probably because the trapped air in the highest point of the pressure line only needs to go 5cm down to get to the master and out in the supply line. And maybe the oil volume used is bigger. This is my last resort of hope to avoid a gearbox overhaul.