Help Me Figure Out Clutch Hydr. Issue
05-05-2017, 06:22 AM
#21
Drifting
Thread Starter
I drove it yesterday for the first time since applying vacuum at the reservoir. It wasn't perfect but it was miles better than how it has felt in the past when sitting for a week. After a few miles of driving it felt perfect again.
I'm at a crossroads on whether to replace the hydraulic line or not. The thing is, if the line was collapsing internally I imagine the behavior would be that the collapse would occur on the return of the pedal when the pressure is lower. This would result in a clutch that wouldn't engage fully and potentially slip. I have he opposite problem.
The bottom line has to be the master or release cylinder are not performing. It's hard to accept that 2 sets both behave the exact same though, which is why I wonder about that hydraulic line as it is the only original part of the system.
I'm at a crossroads on whether to replace the hydraulic line or not. The thing is, if the line was collapsing internally I imagine the behavior would be that the collapse would occur on the return of the pedal when the pressure is lower. This would result in a clutch that wouldn't engage fully and potentially slip. I have he opposite problem.
The bottom line has to be the master or release cylinder are not performing. It's hard to accept that 2 sets both behave the exact same though, which is why I wonder about that hydraulic line as it is the only original part of the system.
05-05-2017, 10:32 AM
#22
Safety Car
When I had mine go out right after I bought the car in 2013 it was a bear getting it air free. I thought something somewhat unconventional but being I'm "stupid" on the subject I didn't pursue it further. I thought about getting some 'an' type fittings from some place like Earls and stainless wrapped hose to replace the hose between the clutch master and slave. I thought if it was fully flexible you could take the slave off the clutch and work it up above the master and bleed it. Once fully bled then work it back down and hook it back up.
Once I found out about using the press and hold the clutch method, it worked out so well I never went back to address it again.
I still wonder what it would take for hose and fittings to hook something like that up? You could get rid of that gooseneck over the master and hopefully have something easier to bleed if the need came up. Plus IIRC a replacement hose was pushing $100 from what I remember (but I won't swear to it).
Once I found out about using the press and hold the clutch method, it worked out so well I never went back to address it again.
I still wonder what it would take for hose and fittings to hook something like that up? You could get rid of that gooseneck over the master and hopefully have something easier to bleed if the need came up. Plus IIRC a replacement hose was pushing $100 from what I remember (but I won't swear to it).
05-05-2017, 11:13 AM
#23
Drifting
Thread Starter
Yep, a reproduction hydraulic line is about $110.
I cant say that what is happening is air. If that were the case, why do I get a good pedal and proper clutch actuation after a bit of driving, as if there were no air? Then the car sits for a week without driving and the symptoms return. There is no leak and the reservoir level does not change. How could air enter? Why only when the car sits unused? If I drive the car today the clutch will feel fine because I just drove yesterday. If I wait a week it will have some much in it for a while the. Return to normal operation.
I can somewhat envision a scenario in which the master cylinder seals leak and allow hydraulic pressure to bypass internally. But again, why after a bit of driving does it correct?
This has truly stumped me. I hate throwing parts at it on guesses. I know the aftermarket hydraulics are suspect (is this industry wide or specific to us?) but to have two replacement sets give identical results has me perplexed. I wonder if I should replace the hose out of process of elimination? I could be throwing $110 doing that but at least if the symptoms persists I will know with certainty it is one of both cylinders and if that turns out to be the case I have no choice but to hunt down oem units and send them off for refurbishing.
I cant say that what is happening is air. If that were the case, why do I get a good pedal and proper clutch actuation after a bit of driving, as if there were no air? Then the car sits for a week without driving and the symptoms return. There is no leak and the reservoir level does not change. How could air enter? Why only when the car sits unused? If I drive the car today the clutch will feel fine because I just drove yesterday. If I wait a week it will have some much in it for a while the. Return to normal operation.
I can somewhat envision a scenario in which the master cylinder seals leak and allow hydraulic pressure to bypass internally. But again, why after a bit of driving does it correct?
This has truly stumped me. I hate throwing parts at it on guesses. I know the aftermarket hydraulics are suspect (is this industry wide or specific to us?) but to have two replacement sets give identical results has me perplexed. I wonder if I should replace the hose out of process of elimination? I could be throwing $110 doing that but at least if the symptoms persists I will know with certainty it is one of both cylinders and if that turns out to be the case I have no choice but to hunt down oem units and send them off for refurbishing.
05-05-2017, 11:15 AM
#24
Drifting
FWIW, I had my original line rebuilt by a local hydraulic hose shop for much cheaper than buying a new one. They even put a nice abrasion resistant sleeve around the braided metal to protect against chaffing and heat.
Jim rebuilt mine a couple years ago and he was a pleasure to work with (through email). Offered lots of great tips, including his method of bleeding. If you’re going to replace both master and slave, here the method I used (based on Jim's recommend) and it worked perfect.
1) Start with the slave first. Leave the clutch master in place with the cap and moisture barrier intact. Unbolt and the slave from the bell housing, leaving the line attached.
2) Bench bleed the new slave cylinder using a small syringe and needle through the line feed port, keeping the bleeder closed. As you input fluid into the feed port, air will naturally be displaced out the port as fluid begins to rise inside the slave. Keep filling until fluid pools at the top of the feed port. There will be no air inside the slave at this point.
3) After the new slave is full, carefully carry it over the car and set aside underneath. Remove the old slave cylinder from the feed line and carefully replace with the new pre-filled cylinder making sure to keep the feed port pointed up so no fluid is lost. Nut the line down to the slave cylinder.
*You should see very little fluid escape the clutch line when you swap, as the cap and moisture barrier are sealing the system from above. This part is key because it will keep the master and clutch line full as you swap the cylinder, letting no air enter that part of the system.
4) Now insert and align the slave rod inside the bell housing and install bolts. If you are just replacing the slave, move to step #6
5) Now move to the master. Suck all the fluid out of the reservoir and remove the line from the master cylinder. The clutch line will still be full of fluid as it is now sealed on the bottom side by the new slave cylinder, meaning there is nowhere for the fluid to drain out. Install new master, attach clutch line and fill with fluid.
6) Now check the pedal…you should have some slight resistance. Even if you have very minor resistance SLOWLY push the pedal 10x or so and you'll start bleeding air out of the system (make sure to have the master cap and moisture barrier removed for this part). Continue to slowly modulate the clutch pedal 40-50 times and you'll eventually end up with a nice firm pedal as the air is displaced.
*one way I was able to verify air escaping is by setting my iPhone to record what is happening at the master cylinder. Push the clutch 10 or so times and then check the video to see if air bubbles continue to rise. When they stop, your done.
I’ve use this method multiple times now and it has proven effective each time.
Jim rebuilt mine a couple years ago and he was a pleasure to work with (through email). Offered lots of great tips, including his method of bleeding. If you’re going to replace both master and slave, here the method I used (based on Jim's recommend) and it worked perfect.
1) Start with the slave first. Leave the clutch master in place with the cap and moisture barrier intact. Unbolt and the slave from the bell housing, leaving the line attached.
2) Bench bleed the new slave cylinder using a small syringe and needle through the line feed port, keeping the bleeder closed. As you input fluid into the feed port, air will naturally be displaced out the port as fluid begins to rise inside the slave. Keep filling until fluid pools at the top of the feed port. There will be no air inside the slave at this point.
3) After the new slave is full, carefully carry it over the car and set aside underneath. Remove the old slave cylinder from the feed line and carefully replace with the new pre-filled cylinder making sure to keep the feed port pointed up so no fluid is lost. Nut the line down to the slave cylinder.
*You should see very little fluid escape the clutch line when you swap, as the cap and moisture barrier are sealing the system from above. This part is key because it will keep the master and clutch line full as you swap the cylinder, letting no air enter that part of the system.
4) Now insert and align the slave rod inside the bell housing and install bolts. If you are just replacing the slave, move to step #6
5) Now move to the master. Suck all the fluid out of the reservoir and remove the line from the master cylinder. The clutch line will still be full of fluid as it is now sealed on the bottom side by the new slave cylinder, meaning there is nowhere for the fluid to drain out. Install new master, attach clutch line and fill with fluid.
6) Now check the pedal…you should have some slight resistance. Even if you have very minor resistance SLOWLY push the pedal 10x or so and you'll start bleeding air out of the system (make sure to have the master cap and moisture barrier removed for this part). Continue to slowly modulate the clutch pedal 40-50 times and you'll eventually end up with a nice firm pedal as the air is displaced.
*one way I was able to verify air escaping is by setting my iPhone to record what is happening at the master cylinder. Push the clutch 10 or so times and then check the video to see if air bubbles continue to rise. When they stop, your done.
I’ve use this method multiple times now and it has proven effective each time.
05-12-2017, 07:19 PM
#25
Drifting
Thread Starter
The clutch has felt pretty good for a while now!
One thing I've wanted to try is reducing the spacer on the clutch master cylinder just a little bit to get slightly more throw on the release bearing. The other day, I removed the spacer, I used a hacksaw to take off a little less than 1/4" and then I reinstalled it.
Today, I thought I'd try it out. Surprise - no start. The reduction on the spacer meant that the clutch start switch was out of whack. I put the car in neutral, removed the hush panel, jumped the switch terminals with a screwdriver while turning the key. Fired right up. The shifter moves nicely through the gears. One thing that's odd, that I don't recall from before is that when I put the car into first gear the shifter goes right in but the car has a tiny forward lurch for split second - and I mean tiny. Like I can feel it but can't see it. Put it in reverse, same deal - tiny backwards lurch. If I put it in 1st then go right to reverse (without allowing the clutch to engage) then no lurch in reverse and same holds true vice versa. So, is this just the act of the synchros moving the gears a touch to align them? Or is this the clutch not releasing in full? I tend to think its the trans lining up the gears. Especially since reducing that spacer size should mean the clutch is MORE disengage.
Now, that aside. I did blindly reduce the spacer. I tried it on a whim based on a thread I read here on the forum. That gentlemen had the entire assembly out and took actual measurements to achieve the correct clutch throw. I don't believe he mentioned anything about the clutch switch not working, but to me that must mean that SOMETHING somewhere is bottom out before the pedal hits the floorboard and that probably isn't good. I imagine it is the master cylinder bottoming but I thought there was a lot of spare throw in it. Either way, before I hacked up my spacer I had purchased a brand new spare just to have on hand in case something like this happened. Looks like I'll be installing it tomorrow morning. To install the spacer you do have to remove the Master Cylinder which is a friggin nightmare because it means removing the clip on the clutch rod/pedal connection. A grueling contorting task under the dash.
One thing I've wanted to try is reducing the spacer on the clutch master cylinder just a little bit to get slightly more throw on the release bearing. The other day, I removed the spacer, I used a hacksaw to take off a little less than 1/4" and then I reinstalled it.
Today, I thought I'd try it out. Surprise - no start. The reduction on the spacer meant that the clutch start switch was out of whack. I put the car in neutral, removed the hush panel, jumped the switch terminals with a screwdriver while turning the key. Fired right up. The shifter moves nicely through the gears. One thing that's odd, that I don't recall from before is that when I put the car into first gear the shifter goes right in but the car has a tiny forward lurch for split second - and I mean tiny. Like I can feel it but can't see it. Put it in reverse, same deal - tiny backwards lurch. If I put it in 1st then go right to reverse (without allowing the clutch to engage) then no lurch in reverse and same holds true vice versa. So, is this just the act of the synchros moving the gears a touch to align them? Or is this the clutch not releasing in full? I tend to think its the trans lining up the gears. Especially since reducing that spacer size should mean the clutch is MORE disengage.
Now, that aside. I did blindly reduce the spacer. I tried it on a whim based on a thread I read here on the forum. That gentlemen had the entire assembly out and took actual measurements to achieve the correct clutch throw. I don't believe he mentioned anything about the clutch switch not working, but to me that must mean that SOMETHING somewhere is bottom out before the pedal hits the floorboard and that probably isn't good. I imagine it is the master cylinder bottoming but I thought there was a lot of spare throw in it. Either way, before I hacked up my spacer I had purchased a brand new spare just to have on hand in case something like this happened. Looks like I'll be installing it tomorrow morning. To install the spacer you do have to remove the Master Cylinder which is a friggin nightmare because it means removing the clip on the clutch rod/pedal connection. A grueling contorting task under the dash.
05-13-2017, 01:25 AM
#26
Melting Slicks
The clutch has felt pretty good for a while now!
One thing I've wanted to try is reducing the spacer on the clutch master cylinder just a little bit to get slightly more throw on the release bearing. The other day, I removed the spacer, I used a hacksaw to take off a little less than 1/4" and then I reinstalled it.
Now, that aside. I did blindly reduce the spacer. I tried it on a whim based on a thread I read here on the forum. That gentlemen had the entire assembly out and took actual measurements to achieve the correct clutch throw. I don't believe he mentioned anything about the clutch switch not working, but to me that must mean that SOMETHING somewhere is bottom out before the pedal hits the floorboard and that probably isn't good. I imagine it is the master cylinder bottoming but I thought there was a lot of spare throw in it. Either way, before I hacked up my spacer I had purchased a brand new spare just to have on hand in case something like this happened. Looks like I'll be installing it tomorrow morning. To install the spacer you do have to remove the Master Cylinder which is a friggin nightmare because it means removing the clip on the clutch rod/pedal connection. A grueling contorting task under the dash.
One thing I've wanted to try is reducing the spacer on the clutch master cylinder just a little bit to get slightly more throw on the release bearing. The other day, I removed the spacer, I used a hacksaw to take off a little less than 1/4" and then I reinstalled it.
Now, that aside. I did blindly reduce the spacer. I tried it on a whim based on a thread I read here on the forum. That gentlemen had the entire assembly out and took actual measurements to achieve the correct clutch throw. I don't believe he mentioned anything about the clutch switch not working, but to me that must mean that SOMETHING somewhere is bottom out before the pedal hits the floorboard and that probably isn't good. I imagine it is the master cylinder bottoming but I thought there was a lot of spare throw in it. Either way, before I hacked up my spacer I had purchased a brand new spare just to have on hand in case something like this happened. Looks like I'll be installing it tomorrow morning. To install the spacer you do have to remove the Master Cylinder which is a friggin nightmare because it means removing the clip on the clutch rod/pedal connection. A grueling contorting task under the dash.
I also recommend using DOT5 silicone based brake fluid in the clutch system (and non ABS brake systems)...and you're right it was a grueling task better left to a circus contortionist...hint take the seat out, its only four bolts, but even then its a b*tch. Good luck!
05-13-2017, 08:41 AM
#27
Drifting
Thread Starter
Mtwoolford, so you didn't run into any trouble with the clutch switch? What I observed under the dash is that when the pedal feels bottomed out it is not on the floorboard and the switch isn't closed. Odd.
Is the DOT5 compatible with DOT3? I didn't think it was. As I understand the DOT5 isn't damaging to things like paint and doesn't absorb water. If I could flush/fill I would - but unsure of the comparability with the DOT3 in the system.
I wish out corvettes had adjustable clutch pedals. My Toyota pickup has a threaded rod connecting the clutch pedal to the master cylinder. It uses 2 nuts to lock in place but it allows one to loosen them and turn the rod to lengthen or shorten to achieve some level of minor adjustment. It really made a difference on the truck for me (that and removing the helper spring that deadens and sense of clutch feeling).
Is the DOT5 compatible with DOT3? I didn't think it was. As I understand the DOT5 isn't damaging to things like paint and doesn't absorb water. If I could flush/fill I would - but unsure of the comparability with the DOT3 in the system.
I wish out corvettes had adjustable clutch pedals. My Toyota pickup has a threaded rod connecting the clutch pedal to the master cylinder. It uses 2 nuts to lock in place but it allows one to loosen them and turn the rod to lengthen or shorten to achieve some level of minor adjustment. It really made a difference on the truck for me (that and removing the helper spring that deadens and sense of clutch feeling).
05-13-2017, 12:13 PM
#28
Melting Slicks
Mtwoolford, so you didn't run into any trouble with the clutch switch? What I observed under the dash is that when the pedal feels bottomed out it is not on the floorboard and the switch isn't closed. Odd.
Is the DOT5 compatible with DOT3? I didn't think it was. As I understand the DOT5 isn't damaging to things like paint and doesn't absorb water. If I could flush/fill I would - but unsure of the comparability with the DOT3 in the system.
I wish out corvettes had adjustable clutch pedals. My Toyota pickup has a threaded rod connecting the clutch pedal to the master cylinder. It uses 2 nuts to lock in place but it allows one to loosen them and turn the rod to lengthen or shorten to achieve some level of minor adjustment. It really made a difference on the truck for me (that and removing the helper spring that deadens and sense of clutch feeling).
Is the DOT5 compatible with DOT3? I didn't think it was. As I understand the DOT5 isn't damaging to things like paint and doesn't absorb water. If I could flush/fill I would - but unsure of the comparability with the DOT3 in the system.
I wish out corvettes had adjustable clutch pedals. My Toyota pickup has a threaded rod connecting the clutch pedal to the master cylinder. It uses 2 nuts to lock in place but it allows one to loosen them and turn the rod to lengthen or shorten to achieve some level of minor adjustment. It really made a difference on the truck for me (that and removing the helper spring that deadens and sense of clutch feeling).
never had compatibility issues with DOT5, of course do not use in ABS brake systems, apparently DOT5 is too viscous to allow the rapid cycling of the ABS solenoids...just drain, pump out the old fluid, replace with DOT5 and bleed until the DOT5 comes out of the bleeder port in a strong stream.
Because DOT5 is more viscous, be careful, pour it in slowly so as to keep entrained air to a minimum, let the fluid sit in the master cylinder to allow any entrained air to come to the surface and escape.
yeah I went through all the misery you're experiencing, finally tried "power bleeding" the system.
got a new (clean) grease gun, replaced the hose with a 1/8 NIP male nipple to 5/16th hose barb combo, attached a soft clear plastic 5/16th hose to the nipple, the 5/16th hose fit tight over the bleeder screw on the slave cylinder, filled the gun with DOT5, pumped it a few times to ensure all air was out (hence the clear hose), attached it to the bleeder screw, power forced the DOT5 into the (empty) slave and on up into the (empty) master cylinder and in 5 minutes (not five hours) had perfect clutch.
There are "power bleeders" available commercially, but my grease gun adaptation cost almost nothing.
On the subject of hydraulic hoses, while I haven't experienced it (yet),I have read that the inner liner can collapse resulting in unexpected problems.
05-14-2017, 08:01 PM
#29
Drifting
Thread Starter
well I had the whole damn thing apart and out of the car, so yes, I probably readjusted the safety switch on the clutch pedal...note..you may want to get a new one as the end of the nylon rod wears down with 20 some years of use, plus it is just a switch and switches do wear out.
never had compatibility issues with DOT5, of course do not use in ABS brake systems, apparently DOT5 is too viscous to allow the rapid cycling of the ABS solenoids...just drain, pump out the old fluid, replace with DOT5 and bleed until the DOT5 comes out of the bleeder port in a strong stream.
Because DOT5 is more viscous, be careful, pour it in slowly so as to keep entrained air to a minimum, let the fluid sit in the master cylinder to allow any entrained air to come to the surface and escape.
yeah I went through all the misery you're experiencing, finally tried "power bleeding" the system.
got a new (clean) grease gun, replaced the hose with a 1/8 NIP male nipple to 5/16th hose barb combo, attached a soft clear plastic 5/16th hose to the nipple, the 5/16th hose fit tight over the bleeder screw on the slave cylinder, filled the gun with DOT5, pumped it a few times to ensure all air was out (hence the clear hose), attached it to the bleeder screw, power forced the DOT5 into the (empty) slave and on up into the (empty) master cylinder and in 5 minutes (not five hours) had perfect clutch.
There are "power bleeders" available commercially, but my grease gun adaptation cost almost nothing.
On the subject of hydraulic hoses, while I haven't experienced it (yet),I have read that the inner liner can collapse resulting in unexpected problems.
never had compatibility issues with DOT5, of course do not use in ABS brake systems, apparently DOT5 is too viscous to allow the rapid cycling of the ABS solenoids...just drain, pump out the old fluid, replace with DOT5 and bleed until the DOT5 comes out of the bleeder port in a strong stream.
Because DOT5 is more viscous, be careful, pour it in slowly so as to keep entrained air to a minimum, let the fluid sit in the master cylinder to allow any entrained air to come to the surface and escape.
yeah I went through all the misery you're experiencing, finally tried "power bleeding" the system.
got a new (clean) grease gun, replaced the hose with a 1/8 NIP male nipple to 5/16th hose barb combo, attached a soft clear plastic 5/16th hose to the nipple, the 5/16th hose fit tight over the bleeder screw on the slave cylinder, filled the gun with DOT5, pumped it a few times to ensure all air was out (hence the clear hose), attached it to the bleeder screw, power forced the DOT5 into the (empty) slave and on up into the (empty) master cylinder and in 5 minutes (not five hours) had perfect clutch.
There are "power bleeders" available commercially, but my grease gun adaptation cost almost nothing.
On the subject of hydraulic hoses, while I haven't experienced it (yet),I have read that the inner liner can collapse resulting in unexpected problems.
I removed the master cylinder yesterday and installed my replacement spacer (unmodified). This did the trick as far as allowing the clutch safety switch to close the circuit and allow the car to start. I hope the day doesn't come that I have to replace that switch. It is buried deep with bundles of wires obstructing my view. My fingers can just get in there place the clip on the clutch pushrod. I don't have much trouble working my body down into the footwell.... its getting out that is getting tough!
Anyway, its back together and I drove it yesterday as well as a bit today. It is shifting great and the clutch feels right. Just maybe this was air all along. The thing that had the most impact for me was applying a vacuum to the clutch reservoir while trying to bleed the clutch using the clutch pedal. It has been consistently good for a while now, probably 10+ days. Next time - I'll be getting that throw away grease gun rather than doing all this. When I next flush the system I may opt for the DOT5, for now it is working and I don't want to fuss with it any more.
and just for fun - here is a pic of the master with the cut spacer vs the replacement. It sure looks like I halved it in the pic, but the slice that I removed was maybe 1/3 of the total thickness. I think the picture is a little deceiving.
