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914World.com _ 914World Garage _ Clutch/flywheel Gurus
Posted by: Joseph Mills May 7 2005, 05:53 PM
The flywheel pictured below has 5k miles on it along with a new pressure plate, clutch disc, throw out bearing, etc.
Clutch slips under full immediate throttle from a healthy four.
What are all the "spots" an indication of?
Attached image(s)
Posted by: bondo May 7 2005, 06:41 PM
It looks like grease or oil got on there, (radial streaks) and contaminated your clutch. Probably the source of the slipping and the spots. (but I'm no expert)
Posted by: Headrage May 7 2005, 06:44 PM
Looks like grease or oil coming from under the flywheel bolts.
Posted by: TimT May 7 2005, 06:45 PM
To much grease in the pilot bearing.
from the amount of grease on the mating surface.. I cant believe your clutch slipped from grease though....
something else is going on..
Posted by: Joseph Mills May 7 2005, 06:57 PM
I guess that the "radial" streaks are from the grease I applied to the throwout bearing and grease I inserted into the output shaft bearing in the flywheel?
I don't see how they relate to all the "spots".
The spots are burned into the new flywheel. This being the first time I have ever done this, I have NO idea what they are. 
And, possibly, more important, what does it mean? 
Posted by: davep May 7 2005, 07:09 PM
The spots look like burn marks. Possibly burnt grease. Did you have the felt seal on top of the bearing?
Was the flywheel resurfaced? Was it resurfaced properly? The height of the mounting surface for the PP from the friction surface is critical. Is the friction disc the correct thickness? Is the PP fully engaging?
Posted by: Joseph Mills May 7 2005, 07:43 PM
Brand spankin' new flywheel.
New disc, pressures plate, etc.
This was done at the same time a top end rebuild was done. I seem to remember the felt seal was properly placed.
So these are "burn" marks?
Posted by: Joseph Mills May 7 2005, 07:47 PM
Actually, I guess I mis-spoke again. 
WHY is my clutch slipping?
Posted by: J P Stein May 7 2005, 08:56 PM
Note the grease (?) has migrated to the outer edge of the flywheel. It had to go around the disc to get there....between the flywheel/disc or disc/pressure plate...or both, but most likely the former.....burn marks are from slippage, me thiinks.
Figure out where the shittage is coming from,
clean up the surfaces and get a new disc.
Posted by: sgomes May 7 2005, 09:50 PM
Can we see a pic of the disk just for the heck of it?
Posted by: SirAndy May 8 2005, 12:31 AM
| QUOTE (sgomes @ May 7 2005, 07:50 PM) |
| Can we see a pic of the disk just for the heck of it? |
show us the disk!
Posted by: Joseph Mills May 8 2005, 12:35 AM
| QUOTE (sgomes @ May 7 2005, 09:50 PM) |
| Can we see a pic of the disk just for the heck of it? |
Hey sgomes
Okay just for the heck of it... here's a pic of the clutch disc...lettering stamp is still there.???
Most likely, I'm just in denial, like the river...
Hard to admit you fucked up...
Although I'd still like to know what I did.
Attached image(s)
Posted by: SirAndy May 8 2005, 12:38 AM
| QUOTE (joseph222 @ May 7 2005, 10:35 PM) |
| lettering stamp is still there.??? |
dude. wtf? how many miles?
Andy
Posted by: Joseph Mills May 8 2005, 12:48 AM
| QUOTE (SirAndy @ May 8 2005, 12:38 AM) | ||
dude. wtf? how many miles? Andy |
5k on the engine, tranny, & clutch.
Posted by: SirAndy May 8 2005, 12:57 AM
| QUOTE (joseph222 @ May 7 2005, 10:48 PM) |
| 5k on the engine, tranny, & clutch. |
looks like your clutch wasn't clutching at all ...
Andy
Posted by: V6914 May 8 2005, 01:28 AM
Even though, it's new, it's the probally the pressure plate, are there any spots or blueing on the plate, the clutch disk, looks to have plenty of meat, the plate provides the clamping force, but the clutch was slipping, so no clamping force.
It looks like it wasn't a whole lot of grease, what there was, was burnt off
Is it the picture? Or is your flywheel missing the alignment pins for the pressure plate (3 0f them)?
Look at your plate, where the T O Bearing rides, all the tangs should be the same height, all the way around, if there are some of them that seem to be lower than the rest, there's your problem. 
There are some heavy duty plates out there, other than the KEP plates.
Posted by: Joseph Mills May 8 2005, 01:55 AM
| QUOTE (V6914 @ May 8 2005, 01:28 AM) |
| Even though, it's new, it's the probally the pressure plate, are there any spots or blueing on the plate It looks like it wasn't a whole lot of grease, what there was, was burnt off Is it the picture? Or is your flywheel missing the alignment pins for the pressure plate (3 0f them)? Look at your plate, where the T O Bearing rides, all the tangs should be the same height, all the way around, if there are some of them that seem to be lower than the rest, there's your problem. There are some heavy duty plates out there, other than the KEP plates. |
Throw out bearing and pressure plate is good to go...(not broken)...
Only weird thing is the flywheel with the spots. I know someone knows what this is.
Well... that's what I'm hopin...fer
post script: I hate to admit it, but I didn't have any alignment pins on hand. That could not possibly be my problem...
Right?
Posted by: Thorshammer May 8 2005, 10:23 AM
They are just what you think they are, Hot spots. See this flywheel is an alloy, a mixture of steels to form a given end product, Those spots are from heat. It is common on a clutch slipping problem as yours is. A couple things that will make a clutch slip. Oil, grease those are simple, But many times the flywheel is new to you but is "rebuilt". one of the most common issues is to get a Bus fylwheel instead of a 914 flywheel which can lead to some very odd clearance issues. If you take a straight edge the spots will be raised just slightly, You may need to have the surface machined.Or try this....
Get a rotary scotchbright pad and clean the flywheel surface, don't be afraid to rough it up a bit. The disc will polish it okay. In the workshop manual there is a depth measurement for the clutch disc surface and I suggest you check it. If the clutch surface has been machined and the pressure plate mounting has not it will reduce the clamping force on the disc. This could very well be the problem. Also, does the clutch pedal move freely and return completely, if not it can stick and reduce the pressure plate force.
When Installing a new disc, just a tiny tiny bit of lube on the pilot shaft is all thats needed, I mean tiny. After that the clutch is a pretty simple piece. Enough clamping force and the proper depth will work wonders. Hope this helps.
Erik Madsen
Posted by: V6914 May 8 2005, 10:49 AM
At, what point in the 5,000 miles did the clutch start slipping? The excess grease you put on the pilot bearing and input shaft, started coming out the first day you started driving, and there couldn't have been that much. (That is grease you wiped your finger through in the picture?)
The alignment pins, are there for a reason, if that was the problem, then the clutch would of sliped from day one, (take the pins out of the old flywheel)
The clutch looks fine, clean it with some Brakkleen, then sand it with some rough paper to clean off any carbon build up. (If you don't want to use this greased soaked disk, send it to me I will 
)
I still think it's the pressure plate
Posted by: Travis Neff May 8 2005, 11:00 AM
Could it be as simple as the clutch being too tight?, depth of the pivot on the throwout arm?
Posted by: McMark May 8 2005, 11:22 AM
What does the other side of the disk look like?
I'm thinking your clutch cable was maladjusted. Did your clutch release the instant you stepped on the pedal? Or was it down near the floor?
Posted by: Thorshammer May 8 2005, 05:54 PM
Yes,
Mcmark does have the same valid points. But also the clutch release pivot point could be off. Or the depth of the flywheel. check it all.
Erik
Posted by: type47 May 8 2005, 06:11 PM
anybody have info on Sachs pressure plates, that is, i found a source of a 215mm sachs pp for very low price and was wondering if they publish the clamping "force" for their products. the pp i found was on a vw bus site. an alternate to the "force" question is: is there a difference between a 914 pp and a 74-75 vw bus pp. (both 215mm)
the clutch disk that they sell is a sachs and it has the 6 springs and the same disc is listed for the bus and the 914; same part number for both applications.
can't find a pp for a bus on any other vendor sites and the source i found lists the disc as a 021.xxx.xxx number, not as a "I2010-xxxxx" listing number like everybody else.
i'd like to save some $ on the 3 clutch parts.... CSOB, that's me......
Posted by: Joseph Mills May 8 2005, 06:53 PM
| QUOTE (Thorshammer @ May 8 2005, 05:54 PM) |
| But also the clutch release pivot point could be off. Or the depth of the flywheel. check it all. Erik |
Thanks everyone for each of your suggestions. I made a list and checked each item.
The clutch cable is new and has slack in it where it connects to the clutch fork. The pivot fork seems to be properly located with space on either side of it at the bell housing. I remember installing the pivot ball all the way in with no spacers behind it.
The pressure plate tangs are even and there are no cracks in the spring pieces and the large rivets are tight.
The flywheel is brand new and has not been resurfaced.
However, I would like to check the depth of the surface to make sure I was provided the right flywheel.
I could not find any info in my Haynes manual.
Does anyone know what exactly I need to measure and what the spec should be?
Posted by: V6914 May 8 2005, 06:57 PM
The Bus 215mm PP and flywheel are different than the 914 215mm PP and flywheel, and the THO bearing, the clutch disk should be the same.
Posted by: Thorshammer May 8 2005, 08:22 PM
Yes The flywheel is different but still 215mm. I believe it is a depth difference between the two. Ed Givler has done this research look on the NHIS race thread he is edgetoo I believe. If you Pm him ,he has the depth figures written down.
Erik
Posted by: davep May 8 2005, 08:47 PM
This is the flywheel specs.
Basically your disc is a 911 disc with the 6 springs. The 914/4 is 4 springs. Normally this is not a problem, and in fact, a benefit. However there are several 911 discs. One, for the 911S with the aluminum PP, is slightly thinner. Please measure the thickness of your disc.
What is puzzling is why it just became a problem instead of being a problem from the start. I would think it has to be related to the grease. That is the only clue we have. Are we sure it is the grease from the bearing, and not oil coming from somewhere else. The O-ring was in the flywheel also? Were there any loose bolts?
Attached image(s)
Posted by: Joseph Mills May 8 2005, 09:17 PM
Thanks for the diagram Dave.
I am going to measure everything tomorrow morning when I have some good light.
I haven't removed the flywheel yet so am not sure about the O-ring or the 5 bolts.
That's a good point about the problem not being there at the start.
It started slipping noticeably about 1k miles ago. I have noticed that it seems to be more prone to slip when the car is hot (like at the AX or a longish drive). This could further indicate it being a oil problem? In that as the oil gets hot, it gets thinner and seeps into the clutch environment?
Posted by: bondo May 8 2005, 09:23 PM
Here's something pretty easy to check that might help narrow down the problem. Install the PP and disk onto the flywheel, but only tighten the bolts finger tight. At this poing the PP should be aboput 1/4" from fully on. As you tighten the bolts, the fingers should move in towards the flywheel. If the PP ends up very close to fully on the flywheel at finger tight, or the fingers don't move as you tighten it fully, something is very wrong.
Posted by: davep May 9 2005, 05:22 AM
Good point actually.
The other thing, are there burn marks on the PP? If the marks are only on the flywheel, then I'd say it has to be the grease. Perhaps it took time for the grease to build up, soak into the disc, and cause slippage. Perhaps most of the friction is now only on the PP side of the disc.
Posted by: Joseph Mills May 9 2005, 05:27 PM
Today I made some real progress. This morning, while examining my various clutch issues, I immediately noticed how slick my clutch disc actually is. Saturday when I removed it, my hands were so greasy it wasn't so noticeable, but with clean dry fingers it was quickly apparent that the disc is saturated. Dragging your thumb across the plate produced a gray/black thumb. Good for fingerprinting.
Also, the pressure plate surface was coated. The entire pressure plate had a film over it. My wife, who smells real good confirmed that it was tranny fluid as opposed to engine oil.
I then removed the throw out bearing, and sure enough, there were signs of fluid seeping around the output shaft seal, and also around the pivot ball that had come slightly loose.
I took the disc to my porsche shop and ran it repeatedly thru their big hot/soapy parts washer, but it seems the disc is still leeching out oil. So it looks like I will be fitting a new disc.
While I was there, I also had them put in a new output seal in the tranny. If this sucker leaks, then I've got other problems (bent shaft/bearings out of spec?).
So tomorrow I should have everything back together.
I guess it will be a month or so before I'll know that the new seal is doing it's job, but hopefully my clutch slipping days are behind me.
Thanks to all for helping me to "grapple" with this mess.
Posted by: McMark May 9 2005, 06:53 PM
Glad to hear it worked out... 
Posted by: Jake Raby May 9 2005, 10:06 PM
It looks as if the disc center was interfering with the flywheel bolts...
Anyway, the off the shelf new flywheels are pretty shitty. I never trust their tolerance from the top to bottom surfaces. I do not see any signs of the disc having grease or oil on it but it has definately been slipping.. Maybe you had it slightly overadjusted. The tell tale signs of that are easy to spot on the surface that the release bearing rides on the pressure plate.. in 5K it should hardly be worn if it was not overadjusted.
The stock set up is good for 160 lb/ft of torque. With my mods to the flywheel I can push 170 through one with a stock disc. After that we can go up to 185 with my feramic disc with the stock pressure plate.. After that the stage II pressure plate is a must but can be used with a stock disc up to 225 lb/ft and thats almost enough to hold my 3 liter..
Also to all you guys changing flywheel seals:
ENSURE that you change the flywheel O Ring when doing the seal.. The O ring is the most likely source of failure and they are very non forgiving... The ones they give you with the gasket sets suck, I have had some made up that are the proper size, not .040 too big like the ones in the gasket sets...
Posted by: Reiche May 9 2005, 10:47 PM
| QUOTE (Jake Raby @ May 9 2005, 08:06 PM) |
| It looks as if the disc center was interfering with the flywheel bolts... |
It does. Oh dear...did you put the disc in backwards?
Posted by: Joseph Mills May 9 2005, 11:10 PM
I don't know how it is supposed to be, but here is what I found.
I placed a straight edge on the flywheel and a few of the bolts catch it just so ever slightly as the straight edge is slid across the face of the flywheel. Letting the straight edge "rock" on one of the bolts, I'd guess it protrudes a few thousands at the most. But as the photo shows on the clutch disc, there is no apparent wear in the area the bolts would contact. Plus that surface is on the back side of the disc pad. By the time it would touch the rivets would be in the flywheel surface. I'm thinking that maybe the bolts were like that originally? I can't remember. Should I hand file them down a bit or just leave them alone?
Are you referring to the "tangs" on the pressure plate that contact the release bearing? There is a slight marking on them but almost no visible wear.
I do know that the clutch cable had a good looseness that was easily moveable between the end of it's housing and the clutch fork.
I will take measurements of the flywheel depth tomorrow and take a close look at how the pressure plate snugs down and moves the tangs as it is tightened as some others have suggested. Maybe you're right and the specs on this flywheel are off.
This story may not be over yet. Damn Clutches.
Posted by: Joseph Mills May 9 2005, 11:12 PM
| QUOTE (Reiche @ May 9 2005, 10:47 PM) | ||
It does. Oh dear...did you put the disc in backwards? |
Nah. It's impossible to put them in backwards. I already tried.
Posted by: McMark May 10 2005, 04:38 AM
I'd also check your pressure plate friction surface for flatness. Seems like the heat damage is only on the outer perimeter.
Posted by: Joseph Mills May 11 2005, 12:40 PM
Installed a new clutch disc last night.
Checked the depth on the flywheel and it measured exactly 22.5mm. Also checked flywheel and pressure plate with a straight edge.
When installing the pressure plate to finger tight, it had about a 1/4" distance. Also measured the location of the tangs with a straight edge. After fully tightening the pressure plate, the tangs had moved nearly 3/8ths inch.
Everything buttoned up real well with no issues with the clutch cable/fork location, etc.
Well, there is one issue. We discovered that my clutch pedal spring is broken. What does this spring do? Does it pull down on the pedal to keep out any slack in the cable, or does it pull up to keep the pedal up (seems the pressure plate itself would do that)?
I put about a 100 miles on the car today and all seems well so far.
And I was pretty successful in resisting the urge to thrash it about.
Posted by: Cap'n Krusty May 11 2005, 01:22 PM
| QUOTE (type47 @ May 8 2005, 04:11 PM) |
| anybody have info on Sachs pressure plates, that is, i found a source of a 215mm sachs pp for very low price and was wondering if they publish the clamping "force" for their products. the pp i found was on a vw bus site. an alternate to the "force" question is: is there a difference between a 914 pp and a 74-75 vw bus pp. (both 215mm) the clutch disk that they sell is a sachs and it has the 6 springs and the same disc is listed for the bus and the 914; same part number for both applications. can't find a pp for a bus on any other vendor sites and the source i found lists the disc as a 021.xxx.xxx number, not as a "I2010-xxxxx" listing number like everybody else. i'd like to save some $ on the 3 clutch parts.... CSOB, that's me...... |
Bus PPs look a lot different than the Porsche ones. The diaphragm is of a different design, and the release bearing is far different. The Porsche bearing doesn't mate up to the PP, and the VW bearing won't work on the 914 tranny. As I recall, the flywheel is cut differently, and the step height may be different. I know GPR sells the VW disc as a "low cost alternative", and I've used one in a "just make it run so I can sell it" situation. The savings isn't worth it, IMO. The Cap'n
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