car jumps forward with clutch disengaged

[Mentow]

*this is not* a simple slave/master cylinder or step height problem, there is something else that we just could not explain, thats why im posting this.

Well it seems like the clutch is not fully disengaging. The car just jumps a few inches forward (yes, the wheels spins, its getting power from the engine) at 7500rpms when i have 1st gear engaged and clutch fully pressed to the bottom.

The first time i had this problem i was using a cheap remanufactured clutch+disc Mitsubishi kit. I´ve replaced it with a Zoom (http://www.perfectionclutch.com/) clutch kit (disc+plate+bearing) which is basicaly an OE replacement, the brand actually is VALEO, its a good brand, or at least it should work just like a new stock kit from mitsubishi.

Here´s what i´ve already checked:

- clutch fork, fulcrum, slave and master cylinder;
- flywheel was stepped first time to .613, then again to .610. I´ve checked once again in a good machine shop to be sure that the flywheel is not warped or have been badly (uneven) machined down to .610;
- to be 100% sure that it was not a slave/master cylinder problem, we kept the fork fully opened (like it is when the clutch is pressed) with a strong pressure plier attached to the gearbox, to simulate a "perfect" clutch release;

This clutch kit im using its suposed to be for and AWD 1g (mine is FWD), but here´s what Zooms said about that: "First of all the difference between the two kits is the release bearing, which could cause some issues. Second, the flywheel step should be -.610, and third, this is an aftermarket stock replacement, therefore this clutch is built to OE specs.". Before you all ask, yes, i´ve replaced the bearing with a FWD one.

What am i missing?

Best regards ers

 

[c4uldr0n]

wow, that is really odd, I wish I had a good answer. Might I ask why you would be revving your engine to 7500rpm with no engine load; that can't be *good*? I'll ask some of my tranny mechanic buddies and see what they think about your issue.

 

[luvmygst]

Are you doing this with the wheels in the air or on the ground? In all reality is not a problem are you ever going to launch a FWD car at 7500rpm? Does the clutch operate normally otherwise?

 

[Mentow]

wow, that is really odd, I wish I had a good answer. Might I ask why you would be revving your engine to 7500rpm with no engine load; that can't be *good*? I'll ask some of my tranny mechanic buddies and see what they think about your issue.

hehehe yeah its really odd.

about revving to 7500rpm with no engine load: i was waiting for the traffic light to go green and joking my friends, when the car suddenly jumped forward. I was not intending at all to launch like that, or else i´d be looking for a new clutch by now

Im not feeling good about that, since it points to a bad disengagement and could lead to a premature clutch disc failure, not to even to mention the tranny syncros..

Regards!

Michel

 

[Mentow]

Are you doing this with the wheels in the air or on the ground? In all reality is not a problem are you ever going to launch a FWD car at 7500rpm? Does the clutch operate normally otherwise?

it happens in both ways, ground and air! While in the air, my mechanic hold the wheel while i revv it, and he easily felt the wheel trying to spin, like a punch or something. If i keep the engine revving, the wheel keeps punching forward.

Well im rebuilding my tranny by now, it was a piece of junk. So im gonna find out if the clutch operates normally only in a few days, but yes, i think the clutch was just fine. But as i just said above, im worried about how that "jumping" could be the sign of premature failure of clutch disc & syncros (which ones will be brand new).

Also as i said above, no, im not lauching at 7500rpm at all hehehe.

Regards!

Michel

 

[housegsx]

Since you've had your flywheel resurfaced twice now, the pressure plate is further away from the clutch release fork than before. So now the throw out bearing will have to go slightly further to fully disengage the clutch. Some common adjustments for this are to shim the clutch fork pivot ball or to use a slightly longer slave cylinder rod. I would recommend doing the shim on the pivot ball, although the transmission does need to come out to do this. Another possible fix would be to get a new flywheel (if indeed this is the problem you're having).

 

[15psi88]

I'd adjust the rod up under the dash, that goes to the master cylinder. I know you said its not some simple slave/master cylinder or step height problem, but i didnt see anything about you adjusting it from under the dash. Since you had your flywheel machined and put a thicker friction disk its probally of adjustment. I had that problem with my 2600, the clutch engaged so close to the floor that if I took ANY pressure off the pedal it would engage immediately. I'm thinking that since you were joking around and not fully paying attention you may have taken some pressure off and not realized it. Anyway, I welded my clutch assmbly up, which might be something you could look into. Found here http://www.dsmtuners.com/forums/showthread.php?t=156805
That seemed to make it a little better, mine is adjusted all the way out and my clutch is still pretty close to the floor, but not right off the bottom anymore.

Take care.

 

[Mentow]

Since you've had your flywheel resurfaced twice now, the pressure plate is further away from the clutch release fork than before. So now the throw out bearing will have to go slightly further to fully disengage the clutch. Some common adjustments for this are to shim the clutch fork pivot ball or to use a slightly longer slave cylinder rod. I would recommend doing the shim on the pivot ball, although the transmission does need to come out to do this. Another possible fix would be to get a new flywheel (if indeed this is the problem you're having).

i understand what you´re saying, its something that i´ll try. But see, it makes me think that is not it (or not just-it), because when i first time had this "jumping-car" stuff, my flywheel was stock (not machined down), with remanufactured disc+pressure plate.

But thanks for saying it.

Regards,

Michel

 

[Mentow]

I'd adjust the rod up under the dash, that goes to the master cylinder. I know you said its not some simple slave/master cylinder or step height problem, but i didnt see anything about you adjusting it from under the dash. Since you had your flywheel machined and put a thicker friction disk its probally of adjustment. I had that problem with my 2600, the clutch engaged so close to the floor that if I took ANY pressure off the pedal it would engage immediately. I'm thinking that since you were joking around and not fully paying attention you may have taken some pressure off and not realized it. Anyway, I welded my clutch assmbly up, which might be something you could look into. Found here http://www.dsmtuners.com/forums/showthread.php?t=156805
That seemed to make it a little better, mine is adjusted all the way out and my clutch is still pretty close to the floor, but not right off the bottom anymore.

Take care.

Thats how me made sure that i was not an adjustment, as i said above:

"- to be 100% sure that it was not a slave/master cylinder problem, we kept the fork fully opened (like it is when the clutch is pressed) with a strong pressure plier attached to the gearbox, to simulate a "perfect" clutch release;"

I mean, the clutch was permanently-and-to-its-maximum disengaged, using the pressure pliers (fork been held to its maximum opening), that way, it cannot be a master/slave cylinder adjustment for sure!

But thanks for posting anyway!

Regards!

Michel

 

[silver eclipse]

It sounds like a bad or warped pressure plate. If it wasnt installed right you can bend or warp the spring causing them to have this effect. If you simulated a perfect release, and this doesnt happen in neutral, I dont see how it would be anything else.
-Chad

 

[Raph]

Bleed the system, then bleed it again,then once more.

 

[Mentow]

It sounds like a bad or warped pressure plate. If it wasnt installed right you can bend or warp the spring causing them to have this effect. If you simulated a perfect release, and this doesnt happen in neutral, I dont see how it would be anything else.
-Chad

I think not since it was me who did it . But i´ll check that, its a good one.

Regards,

Michel