Time for a new clutch MC and blue hose
04-16-2012, 12:23 PM
#1
Three Wheelin'
Thread Starter
Time for a new clutch MC and blue hose - Done
Since the replacement of my slave cylinder last year, I was not able to keep a firm clutch pedal. Air seems to get in the system.
Over the last 3 weeks, I tried every method suggested here to flush the clutch system : Kempf, reverse, power bleeder. Everytime the pedal is firm after the flush but after 2-3 hours driving, it start to feel softer and if I continue driving a little longer, the pedal will not depress completly.
No leaks - in fact, the level in the reservoir is a bit higher.
So I believe it is time to change the MC and the blue hose. I find a nice post from MrMerlin. Anyone tried it ? Comments or tricks that can help?
Thanks
Over the last 3 weeks, I tried every method suggested here to flush the clutch system : Kempf, reverse, power bleeder. Everytime the pedal is firm after the flush but after 2-3 hours driving, it start to feel softer and if I continue driving a little longer, the pedal will not depress completly.
No leaks - in fact, the level in the reservoir is a bit higher.
So I believe it is time to change the MC and the blue hose. I find a nice post from MrMerlin. Anyone tried it ? Comments or tricks that can help?
Thanks
...
In the past week I've submitted an NIH grant, revised a manuscript, and graded a bunch of midterms from my graduate students' immunology course. Here's my edit of what Stan said: (I only did this 'cause I will need these instructions soon and I really appreicate you writing it out, Stan! )
I am working on a 86.5 and part of the job was to replace the clutch master and slave and blue hose.
Given that its usually pretty hard to get out all of the air from the system easily, and not use a whole lot of blue fluid to boot, I removed the whole system from the car:
1. Disconnect the battery, cut the blue hose from just under the reservoir and catch the fluid that comes out.
2. Remove the 2 bolts that hold in the master cylinder.
3. Remove the pushrod from the clutch pedal and also the rubber boot from the master(This is important as keeping the bellows on will make removal difficult).
4. From under the car remove the line holding connection at the swaybar mount , the heat shield at the left exhaust header and remove the 2 bolts on the oilpan that secure the line.
5. Remove the slave-to-bellhousing bolts, remove the starter. The pushrod for the slave should be able to be pulled out of the slave
6. The whole clutch hydraulic system can now be removed from the car.It may take a bit of maneuvering and the top hard line may need a slight bit of bending, not much to get it out.
7. On the work bench refit the new master and slave to the old lines. Pay attention to the orientation of the hoses to the respective cylinders.
8. After this, open the bleeder on the slave and put the master in a vice. Hold the slave so it’s higher than the master. Using an oil pump type can filled with fresh brake fluid, begin filling the master thru the new blue hose till the fluid comes out of the bleeder.
9. Try to move the lines around so as to make sure that any air pockets are moved to the slave. All of the air should purge from the system.
10. Secure the bleeder, and plug the blue line with a clean bolt. Remove the rubber bellows from the new master cylinder and add some tape to the exposed end so dirt doesn’t get into the end when refitting,
11. Refit the whole system into the car starting with the Master. Once the bolts are installed, the blue line should be connected and the reservoir refilled.
12. Secure the swaybar mount, followed by the starter, then the slave to bellhousing.
13. Refit the master pushrod and bellows, adjust so it is not pressing on the master leave about 1 to 2 mm of play .
14. Bleed the clutch with your favorite power bleeder or helper, you should find that the clutch will be high and hard with little or no air , so you will use about 1 oz to bleed it. Don’t hold the bleeder open for more than about 3 seconds as the reservoir may drain, since it’s a smaller reservoir.
15. Reconnect the battery, Done, and no wasted fluid and no skinned knuckles from trying to remove the fittings on the cylinders.
16. As a side note now is a great time to clean out the reservoir. To do this I pulled out the reservoir, drained out the old fluid and sprayed brake cleaner into the res. After doing this I took Simple Green and sprayed this followed by a hot water flush of the reservoir. Then I took isopropyl alcohol and sloshed it a few times, followed by a blow dry with compressed air. Now the reservoir looks like new and all of the old dirt is removed from inside.
If this were for credit, I'd give Stan an A+.
In the past week I've submitted an NIH grant, revised a manuscript, and graded a bunch of midterms from my graduate students' immunology course. Here's my edit of what Stan said: (I only did this 'cause I will need these instructions soon and I really appreicate you writing it out, Stan! )
I am working on a 86.5 and part of the job was to replace the clutch master and slave and blue hose.
Given that its usually pretty hard to get out all of the air from the system easily, and not use a whole lot of blue fluid to boot, I removed the whole system from the car:
1. Disconnect the battery, cut the blue hose from just under the reservoir and catch the fluid that comes out.
2. Remove the 2 bolts that hold in the master cylinder.
3. Remove the pushrod from the clutch pedal and also the rubber boot from the master(This is important as keeping the bellows on will make removal difficult).
4. From under the car remove the line holding connection at the swaybar mount , the heat shield at the left exhaust header and remove the 2 bolts on the oilpan that secure the line.
5. Remove the slave-to-bellhousing bolts, remove the starter. The pushrod for the slave should be able to be pulled out of the slave
6. The whole clutch hydraulic system can now be removed from the car.It may take a bit of maneuvering and the top hard line may need a slight bit of bending, not much to get it out.
7. On the work bench refit the new master and slave to the old lines. Pay attention to the orientation of the hoses to the respective cylinders.
8. After this, open the bleeder on the slave and put the master in a vice. Hold the slave so it’s higher than the master. Using an oil pump type can filled with fresh brake fluid, begin filling the master thru the new blue hose till the fluid comes out of the bleeder.
9. Try to move the lines around so as to make sure that any air pockets are moved to the slave. All of the air should purge from the system.
10. Secure the bleeder, and plug the blue line with a clean bolt. Remove the rubber bellows from the new master cylinder and add some tape to the exposed end so dirt doesn’t get into the end when refitting,
11. Refit the whole system into the car starting with the Master. Once the bolts are installed, the blue line should be connected and the reservoir refilled.
12. Secure the swaybar mount, followed by the starter, then the slave to bellhousing.
13. Refit the master pushrod and bellows, adjust so it is not pressing on the master leave about 1 to 2 mm of play .
14. Bleed the clutch with your favorite power bleeder or helper, you should find that the clutch will be high and hard with little or no air , so you will use about 1 oz to bleed it. Don’t hold the bleeder open for more than about 3 seconds as the reservoir may drain, since it’s a smaller reservoir.
15. Reconnect the battery, Done, and no wasted fluid and no skinned knuckles from trying to remove the fittings on the cylinders.
16. As a side note now is a great time to clean out the reservoir. To do this I pulled out the reservoir, drained out the old fluid and sprayed brake cleaner into the res. After doing this I took Simple Green and sprayed this followed by a hot water flush of the reservoir. Then I took isopropyl alcohol and sloshed it a few times, followed by a blow dry with compressed air. Now the reservoir looks like new and all of the old dirt is removed from inside.
If this were for credit, I'd give Stan an A+.
Last edited by oups59; 04-21-2012 at 06:29 PM.
04-16-2012, 02:21 PM
#2
Rennlist Member
Luc,
I agree that it sounds like a MC problem, air is getting in past the seals.
I've replaced the clutch MC and blue hose on our GT. I tried the method outlined by Stan but on our '90 at least, there was no way to get the MC past the brake booster with the hardline attached. So I disconnected the hardline from the MC, loosened the booster to get a bit of extra clearance, and was able to wiggle the MC out and replace it.
I've never had a problem bleeding the clutch. I use a pressure bleeder (5psi) just to keep the reservoir full, then have my sweety push the pedal down (against clutch pressure). I crack the bleed valve open and and closed again to burp the fluid and air, she releases the pedal, and repeat as needed. (It is easier with the helper-spring removed).
The pressure-bleeder makes sure that the MC refills quickly when the pedal is lifted, and the pedal pressure helps move the fluid through the lines and SC quickly. (I think the pedal pressure also shrinks the air-bubbles and makes then less buoyant, maybe that helps).
I also replaced the clutch hose with one of GB's cosmic hoses, which eliminates the short hardline that snakes between the starter and oilpan.
Cheers,
I agree that it sounds like a MC problem, air is getting in past the seals.
I've replaced the clutch MC and blue hose on our GT. I tried the method outlined by Stan but on our '90 at least, there was no way to get the MC past the brake booster with the hardline attached. So I disconnected the hardline from the MC, loosened the booster to get a bit of extra clearance, and was able to wiggle the MC out and replace it.
I've never had a problem bleeding the clutch. I use a pressure bleeder (5psi) just to keep the reservoir full, then have my sweety push the pedal down (against clutch pressure). I crack the bleed valve open and and closed again to burp the fluid and air, she releases the pedal, and repeat as needed. (It is easier with the helper-spring removed).
The pressure-bleeder makes sure that the MC refills quickly when the pedal is lifted, and the pedal pressure helps move the fluid through the lines and SC quickly. (I think the pedal pressure also shrinks the air-bubbles and makes then less buoyant, maybe that helps).
I also replaced the clutch hose with one of GB's cosmic hoses, which eliminates the short hardline that snakes between the starter and oilpan.
Cheers,
04-16-2012, 02:41 PM
#3
Team Owner
with the procedure outlined above you may have to loosen the booster bolts from inside the car
NOTE dont fully remove the nuts on the top of the booster but remove the nuts on the lower 2 studs.
NOTE your going to possibly have to take the new MC apart and swap in your old piston and old spring while using the new seal from the new MC on the old piston,
Otherwise you can cut 4.5MM off the tip off the new piston and remove 2 coils of the new spring so it wont go into coil bind and fracture
NOTE dont fully remove the nuts on the top of the booster but remove the nuts on the lower 2 studs.
NOTE your going to possibly have to take the new MC apart and swap in your old piston and old spring while using the new seal from the new MC on the old piston,
Otherwise you can cut 4.5MM off the tip off the new piston and remove 2 coils of the new spring so it wont go into coil bind and fracture
04-16-2012, 09:03 PM
#4
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I just completed this job on my 83 US this past week. I replaced the blue hose, MC, SC, and flexible black rubber hose. I also bled the brakes.
The blue hose was leaking as was the MC inside the car. I could not remove the MC without cutting a hole in the wheel well. I took this suggestion from another Rennlister who had a picture of the job. I know that some suggest that this is not the right approach, but I did not want to remove or loosen the brake booster and now I have easy access to the MC should it fail again.
We cut a triangle and bent the metal up to form a "window." From the window, we could see and easlily replace the MC and disconnect/connect the lines. Once you have this view of the MC, you can tell that it could not make its way around the brake booster, at least not in my car. Once complete, I folded the metal back down in place, sealed it with auto/marine sealant, and covered it with rubberized undercoating.
The biggest problem was bleeding. After several power bleeds, any air has somehow worked its way out, or so it would seem.
This is a job that should have taken an hour or two on most other cars. I can tell you that two of us spent a combined 20+ hours on this job. Now I could do it 45 to 60 minutes, but isn't that usually how it works?!
Anyway, good luck!
The blue hose was leaking as was the MC inside the car. I could not remove the MC without cutting a hole in the wheel well. I took this suggestion from another Rennlister who had a picture of the job. I know that some suggest that this is not the right approach, but I did not want to remove or loosen the brake booster and now I have easy access to the MC should it fail again.
We cut a triangle and bent the metal up to form a "window." From the window, we could see and easlily replace the MC and disconnect/connect the lines. Once you have this view of the MC, you can tell that it could not make its way around the brake booster, at least not in my car. Once complete, I folded the metal back down in place, sealed it with auto/marine sealant, and covered it with rubberized undercoating.
The biggest problem was bleeding. After several power bleeds, any air has somehow worked its way out, or so it would seem.
This is a job that should have taken an hour or two on most other cars. I can tell you that two of us spent a combined 20+ hours on this job. Now I could do it 45 to 60 minutes, but isn't that usually how it works?!
Anyway, good luck!
04-21-2012, 06:32 PM
#6
Three Wheelin'
Thread Starter
Well it is done. Not as difficult that I expected. Took about 4 hours.
New MC and blue hose
Should be good for another 10 years 
Thanks for the great info ...
New MC and blue hose
Should be good for another 10 years Thanks for the great info ...
04-22-2012, 12:41 AM
#7
Three Wheelin'
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I disagree here on two points. One lose the blue hose. It is crap and should never have been used in the first place. Pegasus racing sells a red hose for not much money that will far outlast the blue crap from Germany. How come the Germans can not make good rubber??
Second the problem you are having may not be the clutch master. I had an identical problem that drove me nuts. I would bleed it and be fine. The next day the pedal would be at half. Turned out the pressure hose from the master to the slave was sucking in air. When I would bleed it it was fine, but when the car got hot the hose would bleed air into the system. As it cooled over night the fluid would also cool leaving an air bubble in the line.
You can remove the clutch master alone and then use wires to pull the new one back into place. I also found that using one longer bolt to get the cylinder in place made things a lot easier. One it was in place put in the other stock bolt and then replace the longer bolt with the right one. I also use some black window sealer for both the booster and master cylinder to seal the fire wall.
Baring that removing the brake booster will give you plenty of working room. It is easier as a two person job, but I have done several alone.
Good luck
Second the problem you are having may not be the clutch master. I had an identical problem that drove me nuts. I would bleed it and be fine. The next day the pedal would be at half. Turned out the pressure hose from the master to the slave was sucking in air. When I would bleed it it was fine, but when the car got hot the hose would bleed air into the system. As it cooled over night the fluid would also cool leaving an air bubble in the line.
You can remove the clutch master alone and then use wires to pull the new one back into place. I also found that using one longer bolt to get the cylinder in place made things a lot easier. One it was in place put in the other stock bolt and then replace the longer bolt with the right one. I also use some black window sealer for both the booster and master cylinder to seal the fire wall.
Baring that removing the brake booster will give you plenty of working room. It is easier as a two person job, but I have done several alone.
Good luck
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04-22-2012, 09:21 AM
#8
Team Owner
Dan the Blue hose is silicone made by Brembo , its actually a very hi quality hose
Roger sells it about 4.00 a foot you need about 16 inches
Its funny how it lasts about 20 years filled with fluid and still people thinks its service isnt good enough
Put on a new blue hose with your new master and it will work perfectly for another 20 years
Roger sells it about 4.00 a foot you need about 16 inches
Its funny how it lasts about 20 years filled with fluid and still people thinks its service isnt good enough
Put on a new blue hose with your new master and it will work perfectly for another 20 years
04-22-2012, 09:34 AM
#9
Team Owner
oups it would be nice to know if any mods were done to the MC you just installed
IE trimming the piston
IE trimming the piston
04-22-2012, 11:04 AM
#10
Three Wheelin'
Thread Starter
04-22-2012, 11:12 AM
#11
Team Owner
Well the old MC part and new parts are not the same,
and thus the clutch will not fully release in some cases due to the piston stroke being reduced with the new MC,
dont throw the old MC away as you may need to reuse the piston
and thus the clutch will not fully release in some cases due to the piston stroke being reduced with the new MC,
dont throw the old MC away as you may need to reuse the piston
04-23-2012, 05:31 AM
#12
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Dan the Blue hose is silicone made by Brembo , its actually a very hi quality hose
Roger sells it about 4.00 a foot you need about 16 inches
Its funny how it lasts about 20 years filled with fluid and still people thinks its service isnt good enough
Put on a new blue hose with your new master and it will work perfectly for another 20 years
Roger sells it about 4.00 a foot you need about 16 inches
Its funny how it lasts about 20 years filled with fluid and still people thinks its service isnt good enough
Put on a new blue hose with your new master and it will work perfectly for another 20 years
We are hood winked into believing Posche makes quality stuff. Maybe for the newer cars but not the 928. I try to use as much non Porsche rubber as I can find including seals and other rubber parts. I found many replaces for the blue hose but they were quite expensive. Pegaus was the best price and a place to be trusted. Beside the red is far more classy than the faded dirt fabric coated blue.
04-23-2012, 11:05 AM
#13
Man of many SIGs
Rennlist Member
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08-18-2015, 11:33 AM
#14
Three Wheelin'
Thread Starter
I still have problems with my clutch hydraulics.
I am not able to keep a firm clutch pedal. Air seems to get in the system.
Here's the symptoms:
I bleed the clutch system (using Kempf, reverse or power bleeder method). Everytime the pedal is firm after the flush. It stays firm for 2-3 weeks (driving 6-8 hours).
Then, after a couple of days in the garage with the car not running, the pedal is softer. The clutch will not engage as soon as usual.
But after driving 2-3 minutes, the pedal is now firm again.
If I don't bleed the clutch again, one morning the pedal will not be able to engage the clutch.
I change the slave cylinder, master cylinder, blue horse and the pressure hose from the master to the slave.
I am not losing brake fluid. Everything is clean.
The only thing I notice with pressure bleeding , opening the slave bleeder screw, the first drops of fluid is dark.
Is it possible that the bleeder screw allow air to get into the system?
I am not able to keep a firm clutch pedal. Air seems to get in the system.
Here's the symptoms:
I bleed the clutch system (using Kempf, reverse or power bleeder method). Everytime the pedal is firm after the flush. It stays firm for 2-3 weeks (driving 6-8 hours).
Then, after a couple of days in the garage with the car not running, the pedal is softer. The clutch will not engage as soon as usual.
But after driving 2-3 minutes, the pedal is now firm again.
If I don't bleed the clutch again, one morning the pedal will not be able to engage the clutch.
I change the slave cylinder, master cylinder, blue horse and the pressure hose from the master to the slave.
I am not losing brake fluid. Everything is clean.
The only thing I notice with pressure bleeding , opening the slave bleeder screw, the first drops of fluid is dark.
Is it possible that the bleeder screw allow air to get into the system?
08-18-2015, 12:47 PM
#15
Rennlist Member
Another possibility: Check the pedal adjustment to be sure that the MC piston is allowed to come all the way up. The fluid path from the reservoir to the hydraulic circuit is open with the pedal all the way up, allowing the MC to refill as needed and any excess fluid to find its way out. This path gets cut off when the pedal is pushed, as soon as the MC piston begins to travel.
So if the pedal is preloaded too much against the MC then the piston will move a bit down the bore, and the bleed/fill path may be closed all the time. This leads to odd behavior as temperature changes and things expand and contract: Early clutch release when hot (expanding fluid is trapped, pushing on the slave), and a longer dead travel when cold (negative pressure, which will also try to suck in air).
I've also seen a couple of MC's where the bleed hole was blocked with the MC piston all the way up, with the MC out of the car.
See the bottom of this post: https://rennlist.com/forums/928-foru...l#post10387065
I don't know how common this is, but I've seen a couple of cases out of a pretty small sample (maybe three).