There's been lots of discussion here regarding the relavance of the restrictions in the line. I don't want to get into that battle but there is one thing evident: heat plays a role in all of this, based on the reports and the condition of the fluid after some limited use and temps at failure.
I suggest that insulating the line and limiting exposure to the heat will do nothing but help this unfortunate situation. I have some Aluminized Kevlar cloth I am going to cut into a strip maybe 1 1/2" wide and wrap around the line, shiny side out, and secure using SS locking wire around the line in any area in proximity to extreme heat, headers etc. After doing this I will change the fluid (high temp) and see what happens. The fluid condition should give a good indicaton as to what's happening.
If anyone else is interested in trying this I'd like to compare notes to see if there is anything to this. It's going to be awile before I'd have any results being from Buffalo, but will keep you all informed. If there's someone from Arizona, have at it.

 

Well.......the good news is.....you are right.......it helps....the bad news is......it's not the complete solution :confused:

I have swapped out the fluid with high temp crap and insulated the line.....that foot pedal still sticks......it certainly does help though......get better performance than before but there still is a problem.

Damn hydraulics........... :smash:

 

Phan,
Interesting reply, could you elaborate about when you stated, "better performance". Did the insulation increase the time between failures or were the conditions worse re: hotter before trouble developed? Do you have this problem when the system is relatively cool? Does the responce of the system change with temp change? Are you always using the clutch agressivly during occurances?
Sorry for all the questions but knock on wood, haven't experienced this first hand. But is an interesting problem.

Tnks,
Ray

 

Did you remove your restriction yet?


[Modified by MelloYellow, 11:12 AM 2/16/2002]

 

MelloYellow:
Kinda sounds like you and me are thinking the same thing. Restriction is biggest source of problem. :yesnod:
BTW, I just got my line back from Shirl after having been modified. Going to be installed next week during my clutch job at MTI. Can't wait to be free of that PITA line restriction! :cheers:

 

I was looking at mine today about drilling the restrictor, looks like a real pain to get the line off. Anyone done it?

As far as insulating, fluid flows better at higher temperatures so the hotter the fluid is I would think the less likely to have a flow problem.

 

Robert, See my R&R on the clutch line in the Tech Tips section of this forum... My list is short right now so anyone needing the modified clutch line, (eliminates the restriction) email me back...
Shirl :D

 

You need to remove the restriction...period. Chevy is not the only ones that do this Crap! I just read an article in Motor Trend about BMW doing the same thing to their clutch line.

Mine seems to be getting better and better since I removed the restriction

 

Wasn't really looking for an argument with the "remove your restriction" gang. However, I just don't think that that is a complete solution. Granted, I keep hearing reports that it helps. My clutch pedal is still sticking to the floor. Clutch fluid is in pretty good shape. Clutch line is insulated. Remind me again, how is the removal of the restriction a complete solution to the problem? Seriously, I am all ears (and eyes) on this topic. :D

 

I have completely removed the stock clutch assembly, master Cylinder and Slave with a Dual disc McLeod assembly with an Aluminum Flywheel, AP Master and Z06 slave cylinder. This thing grabs like a freaking vise and I have had no problems with it. It is not cheap, nothing great for the C5 is.

Put all of this in your car and you will not worry about a clutch problem again.

vetterdstr :cheers:

 

Robert,
You are generally correct to a point. Once the moisture begins to vaporize you've got a problem, just like brakes. Also, over time, the extreme heat will break down the fluid

ray

 

This may be a silly question but has anyone experienced the problem again after altering the line? Also I thought there were a total of 4 restrictions in the oe line, have we found a way to get rid of all of them or even the worst ones? If not we're not gaining much. A pipe with 10 restrictions all the same size doesn't look much different than one with one restiction that size. "Most" of the pressure drop is taken at the first or smallest restriction. Please don't get mad at me, I'm just asking and trying to help.

Ray

Ray


[Modified by Ray'98, 12:47 AM 2/16/2002]

 

In response to several posts above... Yes, there are 4 restrictions in the line... None of them are small diameter, on the order of 1/8" and only one is in there for the purpose of slowing the clutch action. The others are the result of interface requirements... You could eliminate the two additional ones at the Q/D, but you give up a lot of R&R and bleed capability if you do that. Since the restrictions are not small, the first one does not cause all the problem as postulated above... The restrictions act like resistors in series in an electrical circuit... Each one drops the pressure (voltage!) a small amount... The effect is cumulative. The fact is (based on everyone that has made the change) the modification does help... Is it the total answer? Well no, no one ever said it was, but it does help and it's a pretty cheap mod considering the benefit. If you are looking for the complete answer, replace the entire clutch, slave, line and M/C with after market parts (as posted above) and hold on to your wallet...
I have volunteered to provide the modified line to those that want it because it helped my car and other Vette's... The harder you drive the car, the greater is the need for a fix (any fix)... Suit your self on how you choose to address the problem.
Shirl :D

 

OK, look at it this way, you've got a 10" pipe with three 1" restrictions re: holes to flow through, with a supply pressure of let say 100 psig with some constant nominal flow. When you apply pressure to the system, depending on the flow, you will see something like 90 psid at the first orifice, 4 psid at the second and .5 psid at the third. I didn't do the math but this is somewhat representative of what one would see. Again, if you were to remove the first restriction or any of them the numbers would look the same given the same conditions. First at 90 psid etc..
Electricity is a somewhat different animal. There are some parralels but be careful when drawing conclusions from one another. In fluids there are things like critical flow, friction factors and sonic velocities and others to deal with, it's not as simple as it appears on the surface. As I stated in the beginning of this this is an interesting problem.
As far as replacing everything to fix the problem, that is exactly what you're doing, fixing the problem, not solving the problem.
I'd like to work with you guys to solve this. I've still got a lot of questions if anyone's interested in diving into this. There is an answer but there may not be a fix.

Ray

 

You sure they used a different M/C line or modified the stock one? Your McLeod M/C may have increased capacity that overcomes the restriction. But I think you probably still have the restriction in the line.


[Modified by MelloYellow, 11:15 AM 2/16/2002]

 

No argument. The insulation was worth a try. Do try modifying your line. I think you'll be very happy w/o the largest restriction. It's made a big difference for me. I have zero complaints with my hydraulics anymore.

 

Mello,
Your comment regarding the mods possibly done to the aftermarket parts brings up a question. Has anyone looked inside the master and slave cylinders to see what size the hole is? Not the fitting machining but the cylinder port is probablly drilled to some size. The fitting hole is lets say 1/4" but inside there's a small hole the fluid travels through, what is the size of this hole? If it's a small orifice nothing you do downstream will have much affect. If I were GM this is where I would put a restriction. I'm just thinking out loud, maybe AP took the cylinder and opened this up ( redrilled larger ) to provide more flow and less restriction. That would certainly account for the perceived better performance.

 

I had all the parts shipped to me, then I handed all the new parts for installation to the shop. When the job was all finished I was given back all the old parts. I am quite sure that they used the new parts on my car. BTW, the M/C is an AP unit that is hand built and has no restriction like the stock parts.

vetterdstr

 

Looking into buying a 6-speed C5 soon and this is the first I have heard of this clutch problem... Exactly what does it do or not do? Sounds like the pedal is sticking to the floor or not returning fast enough?

Thanks!

 

Ray, Your example of the 10" diameter pipe with three 1" diameter restrictions may be accurate but it is not representitive of the M/C line... It would be more accurate if you used 8" diameter restrictions in the 10" pipe. In that example, the pressure drop across each oriface would be less dramatic... Actually, your example supports my point in that the pressure 'in' is much less than the pressure coming 'out' and is cumulativly worse as each oriface is encountered... In your (worst case) example, eliminating just one oriface increases the pressure at the outlet substantially... The Corvette clutch line is a low pressure, high velocity system (due to the small cross sectional diameter of the tubing) and is more sensitive to restrictions with regard to transient flow across an oriface. The problem occurs only when the pedal is returning to the top and the only motive force driving the oil back to the M/C is the residual force placed on the slave cylinder by the action of the clutch springs. This is a highly non linear, decaying pressure profile and not well suited for a high transient velocity hydraulic system... Any restriction of the flow damps the clutch engagement and if this occurs under high torque conditions, the clutch will not engage properly... Any aftermarket clutch with a higher clamping pressure would likely have a better force vs distance profile to actuate the slave cylinder more easily overcoming the restrictions in the line. Such a clutch would also contain the high engine torque, preventing slip...
As I said before, you can eliminate the restriction or you can install a stronger clutch... Take your choice... And yes, eliminating the restriction may be considered a band-aid rather than a final solution, but to that I say, 'a solution perceived is a solution achieved'... :D :D :D
Shirl