79 double clutch woes

[Rupesy]

So I started having difficulty shifting a few days ago. It comes and goes. When I first start out in the morning, it seems to shift OK, but after about 5-10 minutes, I have some trouble getting it back into gear on down shifts and at a stop. Sometimes at a stop with he car in gear and clutch engaged, I can feel the disks grabbing. Trying to double clutch doesn't seem to work. The only think that seems to work is if I hit the clutch really fast and all the way to the floor as hard as I can. Then on occasion it shifts fine. If I really hammer it going from third to fourth, the clutch only comes back half way for a few seconds and then it springs back. At this point it's too much of a pain to drive anymore. I am thinking that it could either be the intermediate plate adjustment or possibly leaking (Internally or externally). I was thinking more towards a leak or air bubble.

1. Could it be an internal leak based on the symptoms?? I have looked for apparent leaks on the clutch master and slave and can't see any obvious leaks or drips in the driveway. I still need to pull the slave out and also check the master through my wheel well cut out. However, I have noticed that I have had to put in more brake fluid than I thought on two different occasions and my pads haven't worn that much. I haven't noticed any braking issues so I don't think it got low enough to get a bubble. I plan to give it a good bleeding anyway to see if that helps.

1. Is it normal for the clutch to semi engage within a 1/2" in from the fire wall and then fully engage about a 1/2" from the top (dimensions are guesstimates)?? I notice when I just start coming off the firewall that things start moving. This has been my experience since I have had the car. It never seems to be a problem because there seemed to be enough room between the firewall and when it first engages to not be an issue. Now I only have a fraction of an inch. I am assuming that this could be an intermediate plate adjustment issue. I was planning on doing this adjustment as well.

Any comments or suggestions? I will also post back if I find anything new.

[honerboys]

sounds like a leak either at master or slave - check for leakage inside car where clutch pushrod goes through firewall

[Opelotus]

Could also be the slave cylinder leaking into the bell housing maybe?

Pull the small rubber inspection plug off the bottom of the bell housing and see if it has brake fluid on it.

[Rupesy]

Just posting an update. I got access to the clutch and went through the procedure to adjust the intermediate plate. We'll see if that does the trick. I did not see any leaks on the master or slave cylinder. While I was under there I noticed that the ball and thread for the clutch arm basically comes in and out of the hole indicating that the threads are completely stripped. This may or may not be contributing, but I've got to get it fixed.

Has anyone successfully heli-coiled that ball and thread while the engine is still in place? I was able to get a tap in there to re-tap the threads a long time ago, but it was tight. I knew I would have to address this eventually, I guess now is the time.

Also, is the ball and thread mean to be an adjustment or should it be tightened all the way in?

[Hvithaien]

When you adjust the clutch intermediate plate, be sure to pull the whole assembly out of the car and inspect the splines on the intermediate shaft and in the clutch discs. If these are worn or not correctly lubricated, the adjustment will have little or no effect.

[Rupesy]

Adjusting the intermediate plate didn't help. I had the clutch out and looked everything over and I don't see anything that concerns me. It is properly lubricated. I am convinced my issue is with this stripped ball going into the housing. I can actually wiggle it back and forth is so loose.

Can anyone tell me how difficult it is to remove the bell housing? It doesn't look too bad from underneath. I tried to get a tap started in the hole from the top side, but there is not much room down there. I'm not totally done with giving that a try, but might be worth it to pull the entire housing.

[Danglerb]

Ratcheting tap holder might help, top two bolts on bellhousing will add to your vocabulary.

[honerboys]

I got those top two bell housing bolts out "fairly" easily from the top with a box end on the bolt and another box end (a big one) intertwined with the first - this gave me approximately 18 inches of leverage to loosen them - but the are TIGHT and have been in there 30 years - there are dowels between the housing and torque tube and also I believe between the housing and block - so the torque tube and/or engine need to be "persuaded" for and aft about an inch for housing to clear and drop - I don't know how much give there is in the rubber mounts for tranny and engine so I don't know if it's possible without at least loosening the tranny from it's mounts and supporting it - also remember the tube will have no support up front once housing is removed so have something to support it ready

[Rupesy]

Hardly seems possible to have more vocab added on this car!

Found this while digging and thought it would be good to link for reference. Lots of good pics.

SharkSkin - Shark Attack Round Thirty - Clutch, Torque Tube, Transaxle - Analysis

[rosenfe]

there is a updated ball pivot that is larger in diameter,maybe tapping a larger hole to fit it would work.also loosening trans mounts allows you to move trans back enough to get bell housing out.the ball pivot was an updated item ,as original ball pivot easily broke.

[Arizona_928]

sounds like a leaking clutch hydraulics. Have you tried bleeding the assembly?

That or a bent fork... Went through that on an 944 N/A.

I don't think you have to remove the bell housing. Just drop the bottom BH cover, set the PP spacers, undo the shaft thingy, push back the trans, and drop assembly??

[Rupesy]

Well, I finished up the clutch today. It does seem like it was the ball all along since it was flopping all over the place. Now the ball nice and tight, the clutch seems to run like it used to and I can shift through all gears without any grinding so I am happy about that. I ended up using a heli coil kit that I had laying around that magically worked for the ball threads I had (M8X1.25). I believe I do have the largest ball. Desperation does sometimes breed creativity! Anyway I was able to grind some flats on the tap to make it work. I will admit, I didn't need to drill for the tap because the hole was so wore out, but it did cut nicely. Ball is in there nice and tight. Here are some pics:



Here it is with the wrench on it:



Heli coil fit snug (mirror view):



With that said, I think I am about 95% there. I still haven't been able to find where my brake fluid is going. I can't find any leaks but I have to fill it up on a regular basis. Today I think I may have found the culprit. I saw some evidence that it is leaking between the master cylinder and vacuum booster. I've seen this before on other cars. Ugggg, when will it end. My brakes do feel spongy so it could be that some air did get in my clutch line. Off to the next project! Thanks for all the help and suggestions. I'll post back after I've replaced the master brake cylinder. At least I can drive it around now.

[honerboys]

great job on the helicoil - I like to see people using ingenuity to fix problems -

[AirtekHVAC]

Your blue hose seeping, maybe?

[Danglerb]

I know nothing about that part of the brakes, but isn't the boost to master connection purely mechanical, no fluid? Or are you saying the master is leaking on the booster side?

[Arizona_928]

The master will leak inside the booster. Very very common in the 944's. I don't think it's possible to get a spongy brake pedal from the clutch hydro's. Air would have to go up, then back down. I'm pretty sure a Newton law would be violated. haha
I'm still saying leaking hydraulics, or possibly the rubber gourmets between the res and brake MC?

[Rupesy]

Posting an update. Was working on many other things so let this issue go for a while. The leaking on the booster was in fact the grommets between the reservoir and the MC. Replaced the grommets and it is very dry now.

So the brakes are still spongy. I think since the fluid leaked all the way out several times, I am going to re-bleed the brakes and see how that goes. Otherwise, it's time for a new MC anyway as I think this one could very likely be an original.

I am still fighting the battle with the clutch pedal dropping as I drive. If I am sitting there at idle, it will work properly and I can easily get it into 1st or reverse. I can can sit there for as long as I like and it will work. The minute I head down the road and maintain a constant speed it, the clutch will gradually drop to the floor. If I hammer down, second gear is hard to get into and by third the pedal drops to the floor. When I come to a stop and pump the pedal, it eventually returns to normal. So what I did was to adjust the clutch pedal pivot arm to where it can't be turned out any more. This has made a huge difference and the problem has almost disappeared. Then I bled the cylinder from inside the car which seems to have helped even more. Still happens once and a while while I am maintaining a constant speed, but now if I gently cycle the pedal 3-4 times (not the entire travel, just at the top) the softness disappears and the clutch works OK. So maybe the writing is on the wall for this clutch MC. I'm thinkning its not normal to have the clutch pivot arm all the way depressed since it worked fine previously without that adjustment. I replaced the clutch MC and blue hose about 4 years ago. Not sure if this would be a normal time to change out, but might be worth it at this point.

Also, I found this statement while doing a search posted by hacker-pschorr
"After replacing everything except the pressure plate / release bearing, that was next. What I found surprised eveyone, the locating tooth for the retainer ring on my release bearing was broken off. This was allowing the release bearing to float around, causing the clutch to hang up."

http://forums.pelicanparts.com/porsche-928-technical-forum/478117-clutch-adjustment-what-works.html"]Clutch adjustment.. what works?[/URL]

I'm not sure what this means. Unfortunately the link to the pictures no longer exists on rennlist (at least that I can access). Can anyone explain that? I've had my release bearing off several times before and don't remember a locating tooth??

Thanks, Jon

[Rupesy]

Quick update, went for drive this morning (about 60F) and pedal went to the floor before I started the car. Started it up and after a few pumps, worked OK. Got down the road and it gave me a little trouble here and there. Hit the highway and after just a minute or two the pedal started to go to the floor and then all the way to the floor, nothing. Couldn't even pump it back and forth. It did nothing. Exited the highway and came to the first stop wondering what I would do now. By the time I came to a full stop it had recovered half the pressure and then worked just fine as I sat there waiting for the light. Drove the rest of the way with a little trouble and parked for a minute. Came back out and drove out to the road. Hammered down on my way out and the clutch worked perfectly fine for almost the entire way home for about 10 minutes. Exited the highway and started to have and issue or two, but not as bad as the morning. What is killing me is why I can come to a stop sign and recover all the pressure like nothing was wrong. I can do it every time. As soon as I start moving, it loses pressure. Makes no sense.

[honerboys]

I believe the clutch pedal pushrod should have one turn of preload applied to it - that is .. adjust the rod so there is no free play then turn it one more turn so it's applying some pressure even though the pedal is not being pushed - at least that's how I read it in the manual - is there any fluid down where the rod enters the master?

[Arizona_928]

If it's going to the floor it has an air bubble. I have also ran into problem where the inside piston will stay at the compressed position while the pedal is up... Flashlight will confirm or deny that hypothesis. Get a power bleeder. Put a few pounds look for leaks... Vacuum bleeder might work as well.... You're almost done...