Clutch not disengaging

[DELOREANCHUCK]

I just finished installing a new clutch (pressure plate and disk). The clutch was working fine before the replacement. I did the job because the throw out bearing was shot. I also replaced the pilot bearing and rear main seal. Now the clutch does not fully disengage. I went back and reblead the clutch and adjusted the master cylinder push rod (I have an adjustable one) to give more push. No help. I also looked at the throw out bearing and pressure plate fingers through the inspection opening in the bell housing as the clutch is depressed. There appears to be good movement. If I put the car in gear and then start the engine (clutch depressed) there is a little lurching but I can drive the car.
I don't think it is possible to install the disk backwards. Is it possible the disk is sticking on the splines? Could the pilot bearing be stiff and causing the problem? When I mated the trans with the engine there was no major trouble. Any thoughts?

[DMCMW Dave]

I just finished installing a new clutch (pressure plate and disk). The clutch was working fine before the replacement. I did the job because the throw out bearing was shot. I also replaced the pilot bearing and rear main seal. Now the clutch does not fully disengage. ---

I don't think it is possible to install the disk backwards. Is it possible the disk is sticking on the splines? Could the pilot bearing be stiff and causing the problem? When I mated the trans with the engine there was no major trouble. Any thoughts?

No, the disc won't really fit backwards.

Did you have the flywheel refaced? It's possible to cut the step too big and lose some range. Sticking on the splines would have been pretty obvious during install, it's not a bad idea to test-fit the disc as you install everything.

I hate to say it but I've seen new pressure plates or discs defective out of the box. They are impossible to spot prior to installation. Believe me I've tried to figure out how to spot them (after getting burned). If all else fails you'll need to go back to the vendor.

FYI - Careful with the adjustable masters, it is possible to set it so long that the clutch will never fully engage and will slip (This would be the opposite of your problem so I don't think it's your issue at this time).

[WelmoedJ]

When I needed to renew the clutch disk of 6513 I took the Alpine set (pressure plate, disc, throwout bearing).
The Alpine disc is a bit thicker and after installation the pedal almost had no free play.
Releasing the pedal almost immediately engaged the clutch.
After some 7k Miles it had sufficient free play to fully disengage the clutch.

Perhaps you received a set that's a tad thicker than the ones used by the factory.
If so, it will wear into the right play.

[David T]

After many years of doing this kind of work, one way to prevent this kind of mess is to very carefully examine the new parts and compare them to the old ones. Clean the splines well and try the fit of each part. Make sure the fork is positioned correctly and never force anything together. Even with all precautions sometimes you can still have a bad day. It could be the pressure plate is not adjusted correctly, they are supposed to be set by the shop but they are not always right. It is also possible the clutch plate is not perfectly flat. You have to look for the unexpected.
David Teitelbaum

[DELOREANCHUCK]

First, I did not resurface the flywheel. There were no grooves or burning. I bought the parts from Special T, throwout bearing, pressure plate, disk and pilot bearing.

I could not see anything from the outside so I went and removed the transmission. All the bolts on the pressure plate were tight and the plate was well seated. The only thing I found was that the pilot bearing was free between the disk and the flywheel. It was not in the flywheel hole where it is supposed to be. I do not know if it came out when I removed the tranny or it was that way before. If it was that way before that could account for my problem. There is room for it between the disk and the flywheel without being in the cutout in the flywheel. If this is the case that slight angle 1-3 degrees could cause a incomplete disengagement. What do you think of my theory?
Should the pilot bearing be a tight fit in the flywheel? If is very easy to install and remove. Should i do something to keep it in? Removing and installing the tranny while the car is on ramps is a nightmare not impossible.

Chuck 10610

[Ron]

You should have to drive the pilot bushing into the flywheel (a press fit). I think you may have found the problem (and maybe the cause of the original one...).

[David T]

The pilot bearing would not cause a failure to disengage. It should be a tight fit into the flyhweel. If it isn't you can rough up the internal surface so it is a tight fit or get some Locktite (they make stuff just for this purpose). You have to keep looking for the real problem. Are the hollow locating dowels in the bell housing to properly line up the transmission to the engine? The bolts only hold things together, the dowels (if they are there) are what really lines things up.
David Teitelbaum

[Ron]

THE problem or not, if the pilot bearing is not in the flywheel it can cause spline damage, which can prevent the disk from moving freely, which can cause the disk to drag. (This is common knowledge although David T, self-proclaimed guru, hasn't learned it during his "many years of doing this kind of work").
Less likely but possible, particularly with high mileage transmissions, the input shaft and thus the disk will not be held in alignment and cause the disk to drag.

If the pilot bearing was defective or damaged during installation it can bind/drag on the input shaft preventing it from spinning freely.

[I'm sure I can think of more...Troll on David]

[David T]

The main purpose of the pilot bearing is to give some support to the input shaft and help the transmission stay centered on the engine. Yes, if the bearing is not where it is supposed to be you will have problems, just not the one he has at the moment. This could be a symptom of the real problem though, if the transmission and motor are not properly lined up. My suspicions are that somehow things are not centered but ultimately the only one who is going to find this problem is the original poster. Since he is the only one who can put eyes on it, (and knows what and how he did the previous work) he will be the one to find the problem. This is a little unusual so no one can point to a specific thing as say "Do that". BTW, how does an out-of-place pilot bearing damage splines? I agree damaged splines can affect disengagement but it would take some driving before that happened. Does the Deloreanchuck have a clutch alignment tool? Did he check the fit of the clutch plate on the splines of the input shaft before installing it? Did he have to force things together?
David Teitelbaum

[DELOREANCHUCK]

This morning I took detailed measurements on the shaft, disk, flywheel & crank. I created a drawing and concluded that my original theory is not right. There is not enough space for the pilot bearing to be out of its pocket. If the transmission and the engine are connected right there is only 1/4" between the splines and the lip of the bearing pocket. The bearing is almost 1/2" thick.
I think David you may have hit on the problem. When I installed the transmission and the engine I looked at the bottom of the transmission for contact with the engine but not really looking at the top or the alignment dowels (which are there). It is possible that the dowels may not have seated in the engine and the whole assembly ended up being crooked. I did not have any trouble installing the 2 top mounting bolts. One thing to add is that after completing the job I once had the starter grind. It never did that before. This may indicate a misalignment.
Also the new clutch disk has rub marks around it in 9 places. That's the number of spokes on the disk. Thanks for the replies David & Ron. Thoughts?

[Ron]

BTW, how does an out-of-place pilot bearing damage splines?Similar to misaligning the engine-trans (as you said)...allowing the shaft (which the disk rides on obviously) to flop around will do it too.

Google it, I just got over 200K hits. Here's you a picture.

7901

[DMCMW Dave]

I've seen a couple issues that may bring something to mind.

If you have swapped engines or transmissions between cars, the two alignment dowels may have ended up in the wrong place. They can stay with the engine OR the trans when you pull the trans, and if it's going back together as the same pair it's no issue. If you leave the dowel(s) out the first symptom will be starter grinding noise. There are two and BOTH must be there. This usually happens when swapping transmissions between cars.

If you ignore that starter noise and keep driving, you will either wear out the splines on the input shaft coupler OR you will snap the input shaft (I've seen both). In either case the car stops moving.

I also had a car in that was missing the pilot bearing completely. Same issue - the input shaft wobbled around enough that eventually the coupler rounded out and the car stopped. You could see a shiny area on the flywheel indicating that the clutch disc was "wobbling" in a larger diameter than the disc itself, and the guiy complained about vibration (the disc wobbling). It bell-mouthed the input shaft tube so much it didn't want to come out of the bellhousing, and ground the clutch splines off the input shaft inside the tube.

You have a problem in that your pilot bearing is a loose fit. It must be tight. Unfortunately it is pressed into the crankshaft, not the flywheel. You could *try* using a Locktite adhesive product, as the only other alternatives will be to replace the crankshaft (yeah-right) or sleeve it (difficult to do in the car as you may have to make it larger first).

[Ron]

Two more ways:

7906 7907


Link to same source -- Excellent overview, Failure Diagnosis, lots of pics! (http://www.schaeffler.com/remotemedien/media/_shared_media/library/automotiveaftermarket/brochure_1/downloads_5/luk_schadensdiagnose_traktor_en.pdf)

Adding a grind starter narrows it down, butas said, we probably won't know until it's opened up.


==========

+1 Dave S (on all)
(..."in flywheel"...LOL...My life flashed before my eyes! LMAO...DUH! -- THX)


==========

If it is a little sloppy, knurl it, locate oversized, or do what David TR calls a dirty way and have at it the surface with a center punch...relatively little to loose and I've never known it not to work even on some high horse 386 engines mor than once, FWIW.

[David T]

Now that you are not sure it was properly aligned, it *could* have been cocked at the top and that can be enough to do it. You should reexamine the dowels and when you reassemble make sure the bell housing contacts the engine all the way around. Never count on the bolts to pull things together and line things up. You may have to file and "clean up" the dowels and the mating holes to get things to mate up, especially if you force things. As for the pilot bearing, a couple of well placed pricks with a center-punch on the inner diameter of the hole that the bearing sits in should tighten things up enough. Don't over do it or you will damage the bearing when you install it. I would also use some Locktite but it will make it harder to get it out someday. There is a trick for that too.
David Teitelbaum

[Ron]

I would also use some Locktite but it will make it harder to get it out someday. There is a trick for that too.
+1 ...use the 'sleeve retainer' (green IIRC) rather than 'thread locker' if you can.

[DELOREANCHUCK]

Well I checked everything out while the transmission was out. I found nothing wrong. I reinstalled the transmission. The job took 5 hours. I was working with the rear wheels on ramps and using 2 floor jacks to lift the transmission up. Not a job i want to do again. When I took my first test drive the problem still existed. If I pushed the clutch to the floor it was not disengaging. By chance I was at a red light and I let up on the clutch and I was able to get into gear. I turned out that I had the clutch adjusted too tight. I backed off my adjustable clevis rod and all is well. I never thought that pushing the clutch on too far would cause it to grab. Every time I tested the first installation I would push the clutch to the floor. I'm back on the road and all is well.

Chuck

[jawn101]

Sorry to resurrect an old thread but I need help here too. Over the past two weekends we removed my motor with the transmission attached. Motor got some overhaul work that went well. Transmission also got an overhaul that went well. The problem is with the clutch.

I also got Hervey's new disk, pressure plate, throw out bearing, pilot bearing, master cyl and slave cyl as well as a newly refinished flywheel from DPI.

Installation of everything went well, and since we mated the trans to the motor outside the car it was easy to get everything lined up properly. But we noticed that the pressure plate seemed to be very powerful, which was a bit of a concern at the time. Pressing on, we mated everything up, reinstalled the powertrain, bled the new clutch system successfully and... the clutch WILL NOT disengage. We bled and re-bled the system and adjusted the adjustable clevis on the new master many times. No help. The pedal goes all the way to the floor and the wheels keep right on spinning.

The pressure plate that WAS in the car (does not appear to be original, has 'Brevet.' stamped on it, which is an Italian abbreviation for 'patented') is filthy and pretty glazed/grooved. I don't think it's a good idea to re-use it. The new one from Hervey has 'Made in Great Britain' stamped in it.

I tried DELOREANCHUCK's suggestion of adjusting the clevis *outward* to shorten the throws but that didn't seem to help anything. The slave is moving about 1" (give or take, it's too tight back there to really measure) when the pedal is fully engaged


What should I do?

[David T]

You say the wheels "keep right on spinning". Are you testing the car by driving it or just with the wheels jacked up in the air? The wheels will spin if they are off the ground. Try using the E-Brake to stop the wheels or if you are driving the car should not move under power when the clutch pedal is depressed. If you cannot get full release there is something wrong with the clutch disk, pressure plate, or flywheel. Yes, as you tighten the bolts holding the pressure plate you do apply a lot of pressure to the clutch plate. That is the clamping force that prevents the clutch from slipping. When you pressurize the clutch hydraulics it overcomes the clamping pressure allowing the clutch to slip. If there is not enough room for the clutch plate to slip, the slave cylinder cannot move the pressure plate enough, the clutch will not fully release. Also make sure you installed the clutch fork properly. One thing you can try to do is measure the old pressure plate and compare it to the new one. The dimensions should be close. I would also be calling SpecialT but since you are using someone else's flywheel that can also be the problem. Measure it against your old one and see if it has the correct step.
David Teitelbaum




Sorry to resurrect an old thread but I need help here too. Over the past two weekends we removed my motor with the transmission attached. Motor got some overhaul work that went well. Transmission also got an overhaul that went well. The problem is with the clutch.

I also got Hervey's new disk, pressure plate, throw out bearing, pilot bearing, master cyl and slave cyl as well as a newly refinished flywheel from DPI.

Installation of everything went well, and since we mated the trans to the motor outside the car it was easy to get everything lined up properly. But we noticed that the pressure plate seemed to be very powerful, which was a bit of a concern at the time. Pressing on, we mated everything up, reinstalled the powertrain, bled the new clutch system successfully and... the clutch WILL NOT disengage. We bled and re-bled the system and adjusted the adjustable clevis on the new master many times. No help. The pedal goes all the way to the floor and the wheels keep right on spinning.

The pressure plate that WAS in the car (does not appear to be original, has 'Brevet.' stamped on it, which is an Italian abbreviation for 'patented') is filthy and pretty glazed/grooved. I don't think it's a good idea to re-use it. The new one from Hervey has 'Made in Great Britain' stamped in it.

I tried DELOREANCHUCK's suggestion of adjusting the clevis *outward* to shorten the throws but that didn't seem to help anything. The slave is moving about 1" (give or take, it's too tight back there to really measure) when the pedal is fully engaged


What should I do?

[jawn101]

You say the wheels "keep right on spinning". Are you testing the car by driving it or just with the wheels jacked up in the air? The wheels will spin if they are off the ground. Try using the E-Brake to stop the wheels or if you are driving the car should not move under power when the clutch pedal is depressed. If you cannot get full release there is something wrong with the clutch disk, pressure plate, or flywheel. Yes, as you tighten the bolts holding the pressure plate you do apply a lot of pressure to the clutch plate. That is the clamping force that prevents the clutch from slipping. When you pressurize the clutch hydraulics it overcomes the clamping pressure allowing the clutch to slip. If there is not enough room for the clutch plate to slip, the slave cylinder cannot move the pressure plate enough, the clutch will not fully release. Also make sure you installed the clutch fork properly. One thing you can try to do is measure the old pressure plate and compare it to the new one. The dimensions should be close. I would also be calling SpecialT but since you are using someone else's flywheel that can also be the problem. Measure it against your old one and see if it has the correct step.
David Teitelbaum

Thanks David - yes, we have the wheels up in the air but the open differential is not the reason they keep going. It's actually impossible to get it to change gears after it's in. If I start the car in neutral, I can't disengage the clutch enough to get to first. If I stop the motor and put it in first, then start it up (wheels up), I can't get from first to any other gear.

I do plan on calling John in the morning but I figured I'd go after some other expert opinions. The flywheel is just an OEM one that has been resurfaced, and I trust Josh's work very highly on that.

[Delorean Industries]

I"m still betting on the master cylinder. I had one fight me like this last week.

[jawn101]

I"m still betting on the master cylinder. I had one fight me like this last week.

Well, that's a much easier thing to try than dropping the whole lump again. I still have the original master laying on the garage floor, leaky or not it's still a valid test...

[vwdmc16]

Josh, approximately how much travel should the slave cylinder produce with a good working system?

[LEVY]

You should test your car on the street before you continue any further.

If something got caught in between your clutch disc and either side, that alone may cause the problem you are describing. A little force may release and fix it.

LEVY


Thanks David - yes, we have the wheels up in the air but the open differential is not the reason they keep going. It's actually impossible to get it to change gears after it's in. If I start the car in neutral, I can't disengage the clutch enough to get to first. If I stop the motor and put it in first, then start it up (wheels up), I can't get from first to any other gear.

I do plan on calling John in the morning but I figured I'd go after some other expert opinions. The flywheel is just an OEM one that has been resurfaced, and I trust Josh's work very highly on that.

[jawn101]

You should test your car on the street before you continue any further.

If something got caught in between your clutch disc and either side, that alone may cause the problem you are describing. A little force may release and fix it.

LEVY

I don't know what if anything could have gotten caught in there. Problem I foresee is that it is impossible to get the car out of neutral with the motor running, so with the wheels down I won't be able to get backed out of the garage.

[LEVY]

Whit the wheels on the floor, you should be able to do it.

Just be very carefull in case the car moves while in neutral.

When you have the car on the floor, hit the brake pedal all the way down and try to start (in neutral). If the car start and does not move, then you are OK. If the car is in neutral and does not move, you should be able to shift at will!

If, your car does not move in neutral, then slowly release the brake to see if your vehicle stay still. If your vehicle start moving slowly when you release the brake, then you might need to adjust the clutch a little bit.


Note:

If you still not able to shift, try starting your car in reverse with the cluch all the way down if you can ,(don't know if Deloreans have a safety feature to avoid starting while in gear but I doubt it.).

LEVY


I don't know what if anything could have gotten caught in there. Problem I foresee is that it is impossible to get the car out of neutral with the motor running, so with the wheels down I won't be able to get backed out of the garage.

[Delorean Industries]

I was pushing towards not condeming the new master cylinder. I think you still have air in the system.

[David T]

If you are getting full movement on the clutch slave then your problem is not air in the hydraulics. Easy to verify. Have someone step all the way down on the clutch pedal while you watch the clutch fork. There is NO neutral start inhibit switch on the 5-speeds, ONLY the automatics. That circuit gets jumpered but is still there. Put the car on the ground in neutral, block the wheels, set the E-Brake, step on the clutch and try to start it. If it won't crank and wants to move you have a problem with the clutch. If you want to try it up "in the air" set the E-Brake and try starting it. Make sure the E-Brake will lock both wheels. You can also step on the service brakes. Do not confuse a lot of drag from the clutch with it not disengaging.
David Teitelbaum




I was pushing towards not condeming the new master cylinder. I think you still have air in the system.

[jawn101]

Thanks for all the feedback, guys. I will go home this evening and try some of these tests and keep a detailed log of what I find under what circumstances. But I can say this much - the car starts in neutral, no issue. The wheels don't move (off the ground, on stands) when the motor is running in neutral. But if the engine is running, in neutral, and I depress the clutch to the floor, I can't select a gear. If I select a gear with the motor off and start the engine, it starts but I cannot then depress the clutch and select a new gear. The slave cyl does move, about 1" when the pedal is depressed all the way. What effect that has on the fork is unknown - how can I view that?

[Bitsyncmaster]

Did you measure the old and new clutch plate? I hope this is not your problem but there has been talk of some not machined to proper thickness.

[DMCMW Dave]

Did you have any trouble aligning the disc and getting the transmission installed? A bent disc will do this too, but it will show up as a hard-to-install trans.

[Ron]

FWIW, I just checked the travel on two slave cylinders, both ~3/4". I don't know what brand is in either one of them but, since you are getting 1", I would guess that, if you have it all mated up correctly, you need to open it back up :-(

[jawn101]

Did you measure the old and new clutch plate? I hope this is not your problem but there has been talk of some not machined to proper thickness.


Did you have any trouble aligning the disc and getting the transmission installed? A bent disc will do this too, but it will show up as a hard-to-install trans.


FWIW, I just checked the travel on two slave cylinders, both ~3/4". I don't know what brand is in either one of them but, since you are getting 1", I would guess that, if you have it all mated up correctly, you need to open it back up :-(


Dave M - we didn't measure them specifically, no - but the old friction disk was very worn out and the new one was only very slightly thicker. The pressure plate we didn't really measure.

Dave S - No, no specific issues. We used the correct spline alignment tool and there was no real trouble getting things back together. Like I said, we did it out of the car so it was pretty easy to mate them on the floor

Ron - I was afraid of that, but I don't know what to do when we get in there. :( Should I get another plate from somewhere? Reinstall the old one? I'm at a loss. I didn't get a reply from Special T via email and was stuck in meetings all day so didn't have a chance to call.

[Ron]

Can you elaborate on the trouble you were having tightening the plate?

Did you happen to try putting it in reverse and starting it...if so, I assume the wheels turned?

[jawn101]

Can you elaborate on the trouble you were having tightening the plate?

Did you happen to try putting it in reverse and starting it...if so, I assume the wheels turned?

Sure. Clint (vwdmc16) is my resident genius and mechanic, and he was doing that job while I busied myself with other simple things which I could actually handle, but he said it looked like the gap was larger between it and the friction disk than the old setup was, and also that it took him about 15 lb/ft to tighten the plate down to the motor which he felt was too much.

I was just outside and tried again (wheels still up) to start/run/shift the car. If I start it up in neutral, the wheels do both spin forwards. If I start it up in reverse, they spin backwards. Either way depressing the clutch does nothing to get me out of gear (or into gear if I start in neutral)

Thanks again for all the help guys.

For what it's worth, here are a few photos that might be of value...

[DMCMW Dave]

What I've seen:
-Defective pressure plate - new out of the box;
-Flywheel cut too deep, i.e. the step is too big;
-Bent Disc;
-Cracked (i.e. broken but not all the way) clutch fork.

If the facing was too thick it would do this too. Not likely on a NOS/Valeo disc, possible on an aftermarket (especially aftermarket re-line of a disc with non OEM facing)

[DMC5180]

Who is the maker of that clutch assembly? I've never seen a none Valeo assembly used on the Delorean before. Even the Centerforce clutch I have uses the Valeo Assembly with added finger weights.

[jawn101]

Who is the maker of that clutch assembly? I've never seen a none Valeo assembly used on the Delorean before. Even the Centerforce clutch I have uses the Valeo Assembly with added finger weights.

Sorry Dennis, I have no idea. There was no brand anywhere on the parts. Got it from Special T, the pressure plate was stamped "made in great Britain" but that was the only identifying mark.

[DMCMW Dave]

Who is the maker of that clutch assembly? I've never seen a non- Valeo assembly used on the Delorean before. Even the Centerforce clutch I have uses the Valeo Assembly with added finger weights.

I was wondering the same thing, I've never seen that one. It looks more like the older Valeo (pre-2005 or so) pressure plate design. The disc is quite a bit different as well. Note 6 springs vs 8 on the Valeo.

BTW the current Centerforce plates don't even have the added weights as they won't fit the redesigned pressure plate.

[jawn101]

I was wondering the same thing, I've never seen that one. It looks more like the older Valeo (pre-2005 or so) pressure plate design. The disc is quite a bit different as well. Note 6 springs vs 8 on the Valeo.

BTW the current Centerforce plates don't even have the added weights as they won't fit the redesigned pressure plate.

I really wish I knew what they were, guys :( FWIW, I think I might have taken a photo of the back of the new plate vs the front of the old one.

I just took these shots of the clutch master, it looks like the clevis is backed all the way out for maximum pedal throw to me?

[Ron]

I've never used one of those on a D but it seems all of the way out might use up the beginning of the master's stroke once installed (depending on pedal rest position...).
Did you have to push the rod in any to get the pedal hooked up?

...

After reading through again, I'd have to know the stock slave travel or try the old master setup (A to Z) before pulling it all (...even though a lot of things from a lot of places have been installed.)

As to previous...if it gets to it, I'd start from the crank mating surface and start micing and comparing back if I couldn't see the problem by laying them each on a flat surface side-by-side and/or stacking them.
No, I wouldn't just get a new setup. If you don't find the problem you are prone to taking it out yet again.

[vwdmc16]

I used my video camera to view the travel of my car's clutch slave. Jon definitely has a fully functioning hydraulic system. If anything his clutch arm to being pushed more than mine. Its definitely insufficient clearances between the clutch and flywheel.

[vwdmc16]

Here is the travel of mine, my clutch fully disengages, and try to ignore the horrible squeak

http://s31.photobucket.com/albums/c396/vwdmc16/?action=view&current=MVI_0484.mp4

[jawn101]

Fooled with the master adjustment. Didn't really help much.

I called up Hervey and he's sending out a new pressure plate and a new fork for me to try.

[txdmc]

did you guys ever get this figured out? having the same identical issue.

[David T]

Another possible cause could be putting the clutch friction plate on backwards. I don't know if it affects Deloreans but I do know it can really mess things up on other makes. On some cars it is impossible to assemble the clutch plate incorrectly. Because there is no clutch adjustment the dimensions are very critical. If a reline is too thick it will not release. With that said a new disc can drag a LOT. Driving it a little and putting some wear on it may be all you need to do. I had one Delorean where it was sitting for years and the clutch would not release. The hydraulics were working but the plate had frozen between the flywheel and the pressure plate. Got it to release by getting the car in reverse and hitting the brakes while holding down the clutch. Eventually had to replace the clutch anyway. Another thing to look for is bending or cracking of the clutch fork. This is a bit unusual so you must look for unusual causes. If you had a really hard time getting the transmission back in it could be something done during that install. For instance if you got partway in and let the transmission "hang" on the clutch plate you could have bent it. If you did not check that the clutch plate slid smoothly on the splines it could be hanging up and not floating into it's correct position on the input shaft. On a car once (not a Delorean) I put the throwout bearing on backwards. Needless to say the clutch did not work. Once you make a mistake like that you learn to check and check again for that kind of stuff. You observe carefully when you take things apart and try to make sure you reassemble it the way it came apart. Like Dave S said about the hollow alignment dowels, make sure there is one on each side and that they line things up, VERY IMPORTANT! If it still doesn't work take it out again and try to figure out where it went wrong. It will be a wrong or bad part, a part out of place or installed incorrectly, or you damaged something during the install. All of this assumes the clutch hydraulics are working properly.