Clutch hydraulics driving me nuts
01-15-2012, 03:34 PM
#16
Man of many SIGs
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Hi Doug cutting the tip off the MC is going to involve 2 parts,
one getting the piston cut down,
then also cutting down the spring length.
For the piston you need to measure the depressed depth of the piston do this after removing the new rubber seal what has to happen is the piston only goes far enough into the MC bore so the rear seal wont go past the feed port or it will leak when pushed full bore.
The amount of tip removal will be in the neighborhood of 4 to 5 MM.
Once this is done the next part is to compress the spring to simulate full compression,
what you dont want to happen is for the spring to compress on itself and go to coil bind,
over time this will cause the spring to shatter and thus cut the seals of the MC and the slave.
This may entail removing about 2 coils of the spring, careful measuring is needed for all of these parts.
Once this is done you need to make sure the rest of the poarts your using are new.
If you have not already done get a new flex line for the MC to Slave and a new Blue hose for the MC feed..
Also remove the clevis pin and clevis at the pedal on the pushrod,
make sure these parts have no play if they do have play replace them.
Based on your description of whats happening you have a few issues one is a MC thats not going to full stoke and the other is a weak fluid line thats not holding -pressure when it gets hot.
Also make sure you have the heat shield installed on the left manifold header connection this will protect the flex line from heat.
Following these instructions to the letter should have you back on the road with no more issues
one getting the piston cut down,
then also cutting down the spring length.
For the piston you need to measure the depressed depth of the piston do this after removing the new rubber seal what has to happen is the piston only goes far enough into the MC bore so the rear seal wont go past the feed port or it will leak when pushed full bore.
The amount of tip removal will be in the neighborhood of 4 to 5 MM.
Once this is done the next part is to compress the spring to simulate full compression,
what you dont want to happen is for the spring to compress on itself and go to coil bind,
over time this will cause the spring to shatter and thus cut the seals of the MC and the slave.
This may entail removing about 2 coils of the spring, careful measuring is needed for all of these parts.
Once this is done you need to make sure the rest of the poarts your using are new.
If you have not already done get a new flex line for the MC to Slave and a new Blue hose for the MC feed..
Also remove the clevis pin and clevis at the pedal on the pushrod,
make sure these parts have no play if they do have play replace them.
Based on your description of whats happening you have a few issues one is a MC thats not going to full stoke and the other is a weak fluid line thats not holding -pressure when it gets hot.
Also make sure you have the heat shield installed on the left manifold header connection this will protect the flex line from heat.
Following these instructions to the letter should have you back on the road with no more issues
01-15-2012, 04:32 PM
#17
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You guys are going to eventually get every single one of my "tricks" and then you will no longer need me.....
The most common (and I'm talking virtually every car we see that someone has replaced these pieces and installed a new blue hose has the same problem) is mis-routing the blue hose. I'm guessing, but I'd bet, I've fixed over a hundred cars that have this problem.
This hose must start from the reservour and continuously go down hill, to the master. If it dips below the level of the master...at any point....there will be a bubble trapped in the hose that you will beat yourself to death trying to get rid of this bubble. The master will suck air every time you drive the car, for weeks and weeks. You will eventually be able to get rid of this bubble, but it will very, very difficult and can take a month.
99.9% of the people that do this job leave the blue hose too long and route this hose low or under the power brake booster and then "up" to the master. The correct routing is around the outside of the booster (about 2 o'clock looking at the front of the booster) and then to the master. The hose should gradually go downhill the entire travel of the hose. If any section of the hose is higher than the section it just came from....you have done it wrong.
The good news is that most of the time, one can disconnect this hose at the reservour, reach around and re-route this hose to the correct position, cut off the excess hose and re-attach it at the reservour. A simple re-bleed will then eliminate any air.
I'd guess that this is your problem.....
The most common (and I'm talking virtually every car we see that someone has replaced these pieces and installed a new blue hose has the same problem) is mis-routing the blue hose. I'm guessing, but I'd bet, I've fixed over a hundred cars that have this problem.
This hose must start from the reservour and continuously go down hill, to the master. If it dips below the level of the master...at any point....there will be a bubble trapped in the hose that you will beat yourself to death trying to get rid of this bubble. The master will suck air every time you drive the car, for weeks and weeks. You will eventually be able to get rid of this bubble, but it will very, very difficult and can take a month.
99.9% of the people that do this job leave the blue hose too long and route this hose low or under the power brake booster and then "up" to the master. The correct routing is around the outside of the booster (about 2 o'clock looking at the front of the booster) and then to the master. The hose should gradually go downhill the entire travel of the hose. If any section of the hose is higher than the section it just came from....you have done it wrong.
The good news is that most of the time, one can disconnect this hose at the reservour, reach around and re-route this hose to the correct position, cut off the excess hose and re-attach it at the reservour. A simple re-bleed will then eliminate any air.
I'd guess that this is your problem.....
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
01-15-2012, 05:06 PM
#18
Rest in Peace
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You guys are going to eventually get every single one of my "tricks" and then you will no longer need me.....
The most common (and I'm talking virtually every car we see that someone has replaced these pieces and installed a new blue hose has the same problem) is mis-routing the blue hose. I'm guessing, but I'd bet, I've fixed over a hundred cars that have this problem.
This hose must start from the reservour and continuously go down hill, to the master. If it dips below the level of the master...at any point....there will be a bubble trapped in the hose that you will beat yourself to death trying to get rid of this bubble. The master will suck air every time you drive the car, for weeks and weeks. You will eventually be able to get rid of this bubble, but it will very, very difficult and can take a month.
99.9% of the people that do this job leave the blue hose too long and route this hose low or under the power brake booster and then "up" to the master. The correct routing is around the outside of the booster (about 2 o'clock looking at the front of the booster) and then to the master. The hose should gradually go downhill the entire travel of the hose. If any section of the hose is higher than the section it just came from....you have done it wrong.
The good news is that most of the time, one can disconnect this hose at the reservour, reach around and re-route this hose to the correct position, cut off the excess hose and re-attach it at the reservour. A simple re-bleed will then eliminate any air.
I'd guess that this is your problem.....
The most common (and I'm talking virtually every car we see that someone has replaced these pieces and installed a new blue hose has the same problem) is mis-routing the blue hose. I'm guessing, but I'd bet, I've fixed over a hundred cars that have this problem.
This hose must start from the reservour and continuously go down hill, to the master. If it dips below the level of the master...at any point....there will be a bubble trapped in the hose that you will beat yourself to death trying to get rid of this bubble. The master will suck air every time you drive the car, for weeks and weeks. You will eventually be able to get rid of this bubble, but it will very, very difficult and can take a month.
99.9% of the people that do this job leave the blue hose too long and route this hose low or under the power brake booster and then "up" to the master. The correct routing is around the outside of the booster (about 2 o'clock looking at the front of the booster) and then to the master. The hose should gradually go downhill the entire travel of the hose. If any section of the hose is higher than the section it just came from....you have done it wrong.
The good news is that most of the time, one can disconnect this hose at the reservour, reach around and re-route this hose to the correct position, cut off the excess hose and re-attach it at the reservour. A simple re-bleed will then eliminate any air.
I'd guess that this is your problem.....
