What causes the clutch to stick?
08-09-2005, 12:34 AM
#41
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my theory on this is basically "all of the above"
Heat, clutch disc wear, fluid contamination, line restrictions, improper dimiensions on install, etc.
I dont believe that we will ever be able to look at one persons problems and see what fixed it and say "do that from now on and youll never have a problem"
Just not going to happen.
The problem seems to be with the overall design and I do believe the end result that causes the pedal to stick is heat. I dont believe the car needs to be at a high operating temp to get heat in the slave cylinder. If its possible to weld the disc to the PP on the launch...its possible to get heat in the slave quickly as well. I think some curcumstances make it much worse...and some times I think once you have reached that critical point it becomes easier and easier to get the failure again if some components are not changed.
In other words...I think the problem mostly lies in the slave cylinder and the fluid itself. I think the "donut" in the slave gets caught up either due to expanding fluid/boiling or the "donut" may expand itself due to heat in the bore making it difficult for it to "return". We can always get the clutch to disengage if the hydraulics are working becuase we can put a ton of pressure via the master and pedal. but the return relies on PP spring pressure/slave spring pressure. I think contaminats exasserbate this as well. Contaminates in fluids may change the boiling point.
If you get the slave overheated several times and have boiled the fluid, and its not easily returning to its starting point the clutch may not fully engage with 100% of the PP clamping force. This results in more heat...more boiling...more slave cyl heat...more heat in the PP springs (possibley making them weaker)...more of a likelyhood the PP springs will not overcome the force required to "return" the donut (due to its expansion due to heat)in the slave back to its start point.
So what do we do...change the clutch....it may work for some time...but if you didnt replace the slave it will take a dump much quicker because of the heat that the fluid and slave have already seen.
So we recomend changing the slave everytime with a clutch swap and flushing out all the fluid in the lines and master. I do recomend DOT 5 IMO.
Then others that still have problems...may have mis adjusted dimensions or improper bleeding. This can start the above cycle all over again very rapidly.
Others may simply be overpowering there clutch and getting excessive heat and starting the above cycle as well
Then fianally sometimes the clutches are just plain defective.
IMO the best approach is to use aftemarket free'r flowing lines or the drill mod at a minimum, DOT5 fluid, EXTENSIVE HEAT WRAP, always use a new slave, header wrap, and get a clutch with more holding power than you need.
And anytime you have a problem...new slave, new clutch parts as required, flush all hyd components, bleed using a foolproof method.
I dont think there is anything else that can be done that will be an end all fix all. I think it takes a complete approach.
All this is just my thinking outloud quickly...so take it with a grain of salt.
Heat, clutch disc wear, fluid contamination, line restrictions, improper dimiensions on install, etc.
I dont believe that we will ever be able to look at one persons problems and see what fixed it and say "do that from now on and youll never have a problem"
Just not going to happen.
The problem seems to be with the overall design and I do believe the end result that causes the pedal to stick is heat. I dont believe the car needs to be at a high operating temp to get heat in the slave cylinder. If its possible to weld the disc to the PP on the launch...its possible to get heat in the slave quickly as well. I think some curcumstances make it much worse...and some times I think once you have reached that critical point it becomes easier and easier to get the failure again if some components are not changed.
In other words...I think the problem mostly lies in the slave cylinder and the fluid itself. I think the "donut" in the slave gets caught up either due to expanding fluid/boiling or the "donut" may expand itself due to heat in the bore making it difficult for it to "return". We can always get the clutch to disengage if the hydraulics are working becuase we can put a ton of pressure via the master and pedal. but the return relies on PP spring pressure/slave spring pressure. I think contaminats exasserbate this as well. Contaminates in fluids may change the boiling point.
If you get the slave overheated several times and have boiled the fluid, and its not easily returning to its starting point the clutch may not fully engage with 100% of the PP clamping force. This results in more heat...more boiling...more slave cyl heat...more heat in the PP springs (possibley making them weaker)...more of a likelyhood the PP springs will not overcome the force required to "return" the donut (due to its expansion due to heat)in the slave back to its start point.
So what do we do...change the clutch....it may work for some time...but if you didnt replace the slave it will take a dump much quicker because of the heat that the fluid and slave have already seen.
So we recomend changing the slave everytime with a clutch swap and flushing out all the fluid in the lines and master. I do recomend DOT 5 IMO.
Then others that still have problems...may have mis adjusted dimensions or improper bleeding. This can start the above cycle all over again very rapidly.
Others may simply be overpowering there clutch and getting excessive heat and starting the above cycle as well
Then fianally sometimes the clutches are just plain defective.
IMO the best approach is to use aftemarket free'r flowing lines or the drill mod at a minimum, DOT5 fluid, EXTENSIVE HEAT WRAP, always use a new slave, header wrap, and get a clutch with more holding power than you need.
And anytime you have a problem...new slave, new clutch parts as required, flush all hyd components, bleed using a foolproof method.
I dont think there is anything else that can be done that will be an end all fix all. I think it takes a complete approach.
All this is just my thinking outloud quickly...so take it with a grain of salt.
08-09-2005, 05:11 AM
#42
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_____ i stick my clutch least 2 times a nite!! 
__
-- im gonna try bleeding the fluid and replacing it dot3--
- gonna do drill mod after to c wut happens -
__-- im gonna try bleeding the fluid and replacing it dot3--
- gonna do drill mod after to c wut happens -
Last edited by rice-eatin TA; 08-09-2005 at 05:44 AM.
08-09-2005, 04:26 PM
#43
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Well said 383......I agree that it's not just one simple problem. I my case it's pretty clear that the slave failed. Was the clutch majorly overheated to help this problem along, I dunno,( but I'll find that out when the old clutch is out ) I bought it with 27,000 on the clock . I've never ran it super hard to abuse the clutch itself while I've owned it. My problem was always with cold startup, not while racing ,or under high rpm so I escuse the pressure plate ( wich can and does happen under higher rpms. ) as being the problem. I also agree that each failure needs to be looked at on a case by case basis, but in alot of cases on the 00' f-bods , the faulty part#'d slave design is installed and replacement with an 01'-02' unit fixes the problem ( the 00' part # slave design was discontinued in 01' after a re-design by GM, due to these types of complaints from new car owners. )
Blah Blah........I'm getting off the soapbox
Blah Blah........I'm getting off the soapbox
05-04-2016, 04:02 PM
#44
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What ever the issue is, it has to deal with heat. My clutch never bottoms out when it's -10 outside, but it does bottom out when it's 90 degrees from a simple WOT first to 2nd to 3rd shift when I merge onto a freeway...Then I drive for a mile shitting my pants cause I can't use my clutch to shift gears.
05-04-2016, 05:06 PM
#45
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What ever the issue is, it has to deal with heat. My clutch never bottoms out when it's -10 outside, but it does bottom out when it's 90 degrees from a simple WOT first to 2nd to 3rd shift when I merge onto a freeway...Then I drive for a mile shitting my pants cause I can't use my clutch to shift gears.
05-04-2016, 08:17 PM
#46
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Wow, obviously I still have the same email and am still subscribed to a nearly 10 year old thread! Sadly I read back thru some of this and remember all of this. Been thru a lot of vehicles since this thread!
John
John
05-10-2016, 07:32 AM
#47
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What ever the issue is, it has to deal with heat. My clutch never bottoms out when it's -10 outside, but it does bottom out when it's 90 degrees from a simple WOT first to 2nd to 3rd shift when I merge onto a freeway...Then I drive for a mile shitting my pants cause I can't use my clutch to shift gears.
