Clutch Cable Investigation

BrokeMyCar · 03-22-2007, 07:13 PM

Hi folks,

The other day I pushed down on the clutch, heard/felt a pop, and the pedal stayed most of the way down. I drove home in 1st, and did an inconclusive diagnosis today - tomorrow I hope to lift and look further, and would love some advice on things to look for.

Here's what I've gathered so far about my 82 911SC (190 kmiles):

-the cable is tense at when the pedal is at rest, and stays tense when pushed down the rest of the way (it moves)

-when I pull the pedal up, the cable goes slack

-the spring beneath the pedal _looks_ good, and extends with pedal movement

-the clutch helper spring also _looks_ good

-about 6 months ago I did a clutch adjustment, but found it would go out of whack every time I depressed the pedal - but the clutch felt fine. Clutch Cable Adjust: What's wrong?

-the clutch clevis connection appears solid

Anything I should look for when I lift it? My plan is to pull the cable and see if it's fraying. Also, do Cofle cables not work?

Thanks in advance,

Babak

JTL · JTL's Garage

Could be a broken shear pin in the pedal cluster...

jt
-84 targa

Oh Haha · 03-23-2007, 02:53 AM

The cable cold have stretched from years of use. Check the clevis pin under the floorboard. How many threads are left. You may be able to tighten up the slack with that. Be sure the part that goes through the engine firewall is secure.

If yours is like mine, no amount of tightening would work with my new clutch AND I found several strands of cable frayed. I purchased a new cable and the difference is incredible. Fortunately, I found this while it was in the garage and not on the side of the road somewhere.

psalt · 03-23-2007, 03:21 AM

I would suspect the roll pin in the clutch pedal cross shaft. Try to see if the shaft end moves in unison with the pedal arm over the complete arc. Bronze pedal bushings may be a clue, the aftermarket roll pins that came with many bushing kits are weaker than the factory $1 part. You need to remove the pedal cluster to drive out the pin.

BrokeMyCar · 03-23-2007, 07:55 AM

Great advice folks, I would totally have missed checking the roll pin. I'm guessing the roll pin the same as the shear pin?

Any insight on Cofle cables ($25) vs. Gemo ($75) ones?

Babak

psalt · 03-23-2007, 08:39 AM

I would guess, but a roll pin is designed to hold something together and a shear pin is designed to break to save something. The factory pin is a roll of several layers of metal, the aftermarket part is a "C" of one layer and much weaker. Get two of the factory parts and keep a spare. You should also check the condition of the bushings, especially the one in the eye at the end of the cross shaft lever. When this fails, the lever eye becomes oval and you need a new cross shaft. Once you've identified the problem, the whole cluster comes out and you should clean everything and replace the worn parts.

Don't buy a cheap clutch cable, there are junk copies, even in "Made in Germany" bags. Do a little research, this comes up all the time. A good cable with the later liner last a long time and is worth the difference.

BrokeMyCar · 03-23-2007, 10:30 AM

Today's investigation:

-the shaft pedal and the lever arm appear to move in unison through the whole arc

-disconnected the clutch cable from the pedal assembly; the pedal sank hard, indicating that the spring there is good

-the bushings in the pedal assembly->clutch cable interface look good, and somewhat recently replaced. The hole is nice and round.

-disconnected the cable from the lever arm: it jerked a bit, indicating that the helper spring is ok? (it looks ok)

-pulled out the cable. It looks ok, but I haven't cut into the sheath. Is there a way to see if it's the culprit before I but a new one?

I feel like I haven't found the magic bullet; it'd be nice to know before buying parts.

Thanks folks,

Babak

psalt · 03-23-2007, 10:58 AM

Buying a new cable will not fix the problem if it is the roll pin. The lever arm at the end of the clutch shaft should be around 1 o'clock position with the cable connected and the clutch properly adjusted. If the roll pin fails, the lever arm will be closer to 3 o'clock as viewed down the cross shaft. If your clutch pedal went most of the way down and the cable did not break, the lever must have moved unless the problem is inside the bellhousing. It is not easy to detect a partially failed pin unless you know what you are doing, it is under considerable force. You cannot see the pin until you disassemble the pedal cluster. If the cable and its ends appears OK, try hooking it back up and going through the clutch adjustment procedure.

Oh Haha · 03-23-2007, 11:39 AM

Try doing the adjustment procedure BEFORE buying anything. Maybe you could post a picture of the cable and the cluster so we could see what you do.

EDIT:
Did you check to see that the end of the cable is secure at the firewall? If it isn't, your adjustment will not "keep".

BrokeMyCar · 03-23-2007, 12:01 PM

The cable is out now, but it did require quite a tug to come loose at the firewall. That means it was probably pretty secure before. Without the cable's load the lever arm is at about 1 o-clock when the pedal is pulled up to flush with the brake pedal.

I'm out of time today, but after the weekend trip I'll put the cable back in and try to do an adjustment. I think I recall JW saying I should thread it 8mm into the clevis. I'll do that, then shim, take pictures and report. Thanks guys-

Babak

BrokeMyCar · 03-28-2007, 04:58 PM

So I put in the old clutch-cable and tried adjusting it as follows:

-at the clevis, 20mm from the end of the cable to the far side of the nut
-before attaching the clutch cable, 1.2mm clearance set at lever
-after attaching the cable and pushing the pedal down I couldn't adjust the two nuts to get ANY clearance at the lever
-I adjusted the cable's two nuts all the way to the extreme, and the pedal still doesn't go all the way up (it's nowhere near flush with the brake pedal)

Clearly I'm still at a loss... help!

I've attached some pictures, but this video shows it well:

http://www.youtube.com/watch?v=ts3xUKhKwNs

The clutch adjusted to the extreme:

How the clutch cable is routed:

Where the pedals sit at this adjustment:

A picture at the pin:

The omega:

jtfreels · 03-28-2007, 05:34 PM

My two cents, doesn't quite match the problem you state in the first post but......
I had a similar problem, driving and pushed down on the clutch, large POP sound. The pedal helper spring was broken, so was the roll pin in clutch pedal. After I fixed those, I still had problems... lon g story short, the throwout arm at the tranny had cracked. Up till I dropped the engine to find this I could get the cable tight but of course never get it adjusted properly.

Good luck.

Jay

Oh Haha · 03-28-2007, 06:29 PM

The helper spring is not in the correct position. It should just about touch the heat exchanger.(notice the cutout in the heat exchanger) Try adjusting the cable nuts on the trans bracket the other way just enough to get the helper to spring all the way back.

You may also want to thread the clevis end on a bit more if this doesn't help.

EDIT: Do have anyone that could work the pedal while you observe what's happening at the trans? It helps to see what moves and how much.

BrokeMyCar · 03-28-2007, 08:32 PM

Good idea! I didn't have a friend handy so I put the camera and a bike light under the car and pushed on the pedal.

The clutch helper:
http://www.youtube.com/watch?v=KCxNEbwUhAU

The small lever:
http://www.youtube.com/watch?v=iiCQLdk7n_o

Is the clutch helper spring supposed to move like that? If I pull back on the pedal the cable goes slack, and the helper spring doesn't go any closer to the heat exchange. Does this mean the helper spring isn't attached the way it should? Should the small lever arm be flush with the big one?

It looks like the throw arms are solid. Is there another throw arm inside the bellhousing?

Thanks,

Babak

Oh Haha · 03-29-2007, 03:19 AM

Did you pry the helper spring into place after reinstallation? If not, disconnect the cable and using a big ol' screwdriver pry it into place. It should "snap", almost touching the HE. After that, you can adjust the cable. Sorry, I just assumed you did that.

BrokeMyCar · 04-03-2007, 12:01 PM

I took another swing at it today. With the clutch-cable disconnected I set the set-screw to 1.2mm. Realized the holding nut is on the wrong side, but there's no room in there to take it out! I gotta find another nut to put on the right side. I then pushed the omega spring back as far as it would go, reconnected the cable and tried to adjust. Went all the way down to the hairy edge of the adjustment (see the pic below). During the adjustment the omega moved bit by bit. Eventually I got 1mm at the set-screw.

To be sure, I then pushed the omega until it hit the heat exhangers:

When I stopped pushing it returned a little:

Then I went to the car and saw the pedal was nice and flush with the brake pedal. I pushed down on it, during which the camera under the car saw this:

The pedal didn't return all the way up - and looking under the car I saw the omega wasn't where I'd started it:

Should the omega be moving that much? That I'm at the end of my adjustment indicates I should probably get a new cable, but I can't help but feel something else is wrong. Thanks so much for your help guys, super super appreciated-

Babak

PS there's a movie too, if anyone wants to see

Danskman · 04-03-2007, 02:32 PM

Quote:

Originally posted by BrokeMyCar
Great advice folks, I would totally have missed checking the roll pin. I'm guessing the roll pin the same as the shear pin?

Any insight on Cofle cables ($25) vs. Gemo ($75) ones?

Babak

Just to cover this question... Gemo is the OE supplier to many Euro car manufacturers. Their factory for control cables (brake, clutch, accelerator) is located in Berlin. Factory for rotary cables/flexible shafts (tach, speedo, seat, sunroof) is located in Krefeld. In addition to Dansk, I rep Gemo in the USA and Canada.

Cofle is an Italian cable manufacturer. Much less expensive, nowhere near quality of Gemo. I have done comparisons for similar applications, and in many instances Cofle will use plastic where Gemo has used metal, number of steel threads is less, and some design liberties have been taken.

If you have a choice, Gemo is the quality manufacturer.

BrokeMyCar · 04-24-2007, 11:03 PM

Just in case anyone is subscribed, or maybe stuck with similar symptoms, I thought I'd bring this story up to date. The car's running great now, and the clutch feels better than ever! Here's what I think happened (please feel free to correct me if I'm wrong):

1) The leaflets of my helper spring (omega) became bound, a long time ago, and it lost its strength (which is why my previous clutch adjustments wouldn't hold, Clutch Cable Adjust: What's wrong?).

2) The day of the incident the spring (somehow?) flipped away from one minima, near the heat-exchange, to the minima closer to the center of the transmission, as Wayne so astutely observed.

3) This dropped my clutch pedal to far lower than I expected, but explains why further depression let me roughly change the gears.

I thought I'd just have to replace the helper spring, but in trying to take off the lever arm I discovered that my car is one of a minority of 82 SCs that have a lever arm with a circlip AND a tapered pin! (Throw-Out Arm Removal: Leverage?) In the process of removing the pin, and the exhaust cross-over to get to the pin, I had lubricated/exercised/heated much of the area. Somehow though all this, the helper spring leaflets unbound, and the spring had oomph again! I replaced the clutch-cable, and with some effort I pushed the helper spring into place against the heat exchangers, where it stays put now. The clutch adjusted properly, and kept its adjustment, for the first time.

I'll probably move the pedal-stop back a bit more (I replaced the rubber bit and now it feels short), but I went driving around tonight and the pedal felt and worked great! Thanks again to everyone for the help, troubleshooting, ideas and support.

Babak