I need some opinions from my fellow trackies. I was at Mid Ohio this past weekend and coming through thunder valley I pushed my clutch in to shift to 4th and it didn't shift. I lifted my foot to push the clutch in again and the pedal stuck to the floor. I came in to the pits and checked everything out. I bled all my fluid out and put new stuff in. It was coming back a little bit but not all the way now. I adjusted the rod that connects to the master cylinder and I was able to get it to work, but now I smell burnt clutch at idle. I think my pressure plate is busted or something. If I put the rod back I only get half dis-engagement. I climbed under the car and checked. The slave cylinder rod moves anytime the clutch pedal moves. There is no play in it, it just doesn't come back all the way. I am gong to tear the tranny out this weekend to find out for sure, but I just wanted some ideas.

Thoughts?

 

Sure sounds like a hydraulic problem....what fluid are you using?

 

Well, I totally forgot that I was using "stocker" style fluid for the clutch, but after I bled it, I used Motul RBF 600 which is what I use for my brakes.

 

....and the issue didn't improve from switching fluids?

 

Clutch master is needing a rebuild. My 05 does that all the time. Rebuild kits are on back order right now. Maybe just pull it apart and clean it out for now.

 

What year is your car? The HR's use a concentric slave cylinder that seems to be a problematic part. The seal in it is stationary and seems to roll over and tear.

 

I've had a clutch pedal hanging up on hot days at the track, usually not until the afternoon, for probably 2 seasons now (this is the car's 6th year as track car & DD). Motul's been used since new, but I've always figured it was still heat/fluid related. Last year the slave & master were replaced. Two weeks ago it started hanging up in the afternoon at Grattan Raceway. Right now it's in the shop for a new clutch. With the car running in neutral you can hear a squeak from the throwout bearing when you move the clutch pedal and it recently added a click sound that transmits a feeling thru the pedal. So there's some unpleasant movement in there, even tho it still pulls hard to redline without slipping. Hopefully yours will be a cheaper easier fix. Altho I've gotta say I'm looking forward to a lighter flywheel and a stronger than stock clutch.

 

My car is an '04.

When I switched the fluids it got better, but not back to normal.

I thought I just cooked the fluid because it was early in the afternoon and it was really hot and humid out. Once I bled it, it would come back up now, but only about halfway. I also now have some vibration. I have an RPS clutch and their segmented flywheel. I put it in last year. Hopefully I will have time this weekend to pull the tranny and take a look. Pulling the tranny isn't too bad. I've done it twice before. I need the car to be driveable again by October. I am planning on doing the last NASA event of the year at Putnam and I want to get signed of to HPDE4 so I can do TT next year. I was planning on doing it at Mid Ohio on Saturday, but the clutch went out. Thanks for the input guys. I'll let you know what she looks like once the tranny is out.

 

I bet if you cooked the fluid, you also cooked the t/O bearing.

I'd be more then happy to take a look at the clutch if you have any questions about it. I can give you actual plate load, clutch release measurement. I can also check for taper in the flywheel/ pressure plate from warp. For free of course. (SEE PICS)

FYI, I'm not trying to sell anything, just trying to help a fellow enthusiast get his problems figured out.

 

You're fine....

 

What exactly does a cooked T/O bearing look like? Thanks for your help guys.

 

When you spin a t/o bearing by hand, it should have some resistance. If it spins freely, then the grease may be broken down due to heat. Another way to tell would be discoloration. Bearings are generally a brighter silver color. So if it's a gold tint or blueish, then it got hot. Is there any grease coming out of the bearing? If so, what color is it. Black would indicate burnt grease. You should also be able to smell burnt grease. Despite all of this, it's a cheap maintenance item. If it where to completely go out, it would possibly cost you a race.

I think Nissan brake/ clutch fluid has a higher boiling point then the type of grease in the bearings anyway. I think the bearing is like 300 deg and the fluid is 350-400 deg. Plus calculate distance the heat traveled to get back to the hydraulic fluid. Whereas the clutch and engine heat are touching the t/o bearing. Come to think of it, i wonder what the operating temps are for the input shaft seal and the rear main seal. It's all right in the same area.

 

Ha I've got the same issue that z3305 has with the squeak and click. Tearing my tranny out this weekend and putting in jwt clutch and flywheel plus new t/o bearing, pilot bushing, chromoly clutch pivot ball?, SS clutch line and rear main seal. Also swithcing transmission fluid to royal purple 75w-90. Has anyone had issues recently with trying to get ahold of a clutch alignment tool? Apparently they're on a minimum 4 week back order. My kit didn't even come with one but thankfully my buddy had one left over from when we replaced his clutch in his 240sx thankfully they use the same tool. I just had to drive 100 miles out to his new place to get the damn thing but thankfully I enjoy a nice road trip everynow and then.

 

Some local auto parts stores carry a universal kit. I've seen guys use a pen and a roll of electrical tape.

 

Well I finally got the tranny pulled and um....yea. The damn friction surface on the clutch pretty much just broke down into pieces and flakes. The pic shows the piece that stayed in tact. It was loose anyway. When I pulled on the pressure plate the leftover friction surface just fell out. Good stuff. Needless to say, I'm ordering a new clutch.

 

Which clutch are you going to replace it with?

 

Well, I have an RPS segemented flywheel and I think their clutches only work with their flywheel. The flywheel looks good to me. I am going to replace the friction surface on it and get a pucked clutch from them. I pretty much just road race the car. I almost never drive it on the street. I will have to though to break in the new clutch.


Also, the forks on the pressure plate are bent pretty bad.

 

Even given the abuse....I would be hard pressed to put another clutch of the same brand in after that result. Just my .02.

 

I was thinking the same thing actually. I just don't want to buy another flywheel. I need to get it back together asap for cheapest route. I did just buy their high end race clutch. We'll see how it does. If this one blows sooner than it should I will probably go with a JWT or if I have the money an Exedy. I also bought a GTM pivot ball since I got the tranny out.

 

Single rivet attachment blows.....

Southbend disks use a dual rivet facing that makes the disk facing much less likely to break off their mounting points. This material is made for southbend clutch exclusively. They could not find a dual rivet lining in the 250mm that they trusted to hold up so they had this made to use in the nissan 250mm clutch kits.


This is a South Bend DXD Rally Clutch facing.
Also notice how much copper is in the lining..
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Back of clutch facing, This really shows the amount of material in this facing.
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This is a 300zx Twin turbo kit but the same disk is used in the 350Z/G35 kits.
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Most companies use a small amount of copper with a lot of fiberglass strands to fill the disk facings, Fiberglass is cheap and holds little TQ.

Sample of other companies clutch disk.
Notice only a single row of rivets to attach the clutch facing to the hub and a very small amount, if any, copper weave.
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Again....