Clutch mystery

[Christopher smith]

 

Looks like I found where the noise is coming from. The nasty looking scrapes on the clutch disc splines  are all I see so far that might make the noise. The input shaft for the pinto trans looks and feels fine. Still hoping to understand why it worked fine for years of mild use but now gets nasty after maybe 8 to 10 starts since I put in a new replacement slave cylinder and release bearing. I did not change the clutch or pressure plate when I put in the new slave and release bearing since it probably only had maybe 500 miles of mild use. Almost seems like the splines on the trans input shaft do not go far enough into the clutch splines and when it gets used (or gets warm?) it is not far enough in maybe . I will take it further apart and take a lot of measurements. Any ideas?

[wdb]

https://www.fcpeuro.com/products/clutch-disc-spline-grease-80-gram-tube-sachs-4200080050?ads_cmpid=20892570397

 

 

[MV8]

I think most of us are expecting the "grinding" noise to be gears not meshing. How about a video?Is the new slave and bearing different in any way to the old ones? I don't see anything seriously wrong with the clutch splines. You can put the clutch on the input shaft and slide it back and forth to feel if it binds and rock it on the splines to check the engagement. Use gloves or a clean rag to handle the friction face. Any metal dust? Shiny spots on anything like the crank bolt heads? Is the main case as warm as the bell? Did you check the trans fluid like I suggested? The clutch has a flywheel side and a trans side.

[Christopher smith]

Many thanks for the input.The clutch slides on the input shaft splines fine- slides easy and no wobble but was not lubricated. I did notice the friction material may have worn and the surface is just 1.5-2 mm from the  recessed brass rivets. No signs of abuse. No metal powder and very little black dust. The trans side of the disc is the protruding side. No signs of heat or wear on the pressure plate or flywheel surfaces either.  Pilot bearing has about 1-1.5 mm clearance on the trans input shaft diameter and still has grease. So not sure why,  but seems it is not disengaging when used a bit or hot maybe. And not sure why it worked fine for years and only developed these symptoms when I replaced the master, slave and release bearing. Unfortunately I discarded the old release bearing so can not measure but the originals and replacements were Bean Engineering so I presumed the same. The slave measures the same. did not check the trans oil yet. I am pushing 80 and my very hot garage has slowed me down.

[toldfield]

Call Ken at Dave Bean and describe what is happening.  He is a great resource and fountain of knowledge.  

 

tom

Edited August 3 by toldfield
correction

[Christopher smith]

Thanks- I was planning to call Ken on Monday. Made some more measurements just now and maybe the spacer behind the slave cylinder was set for a thinner release bearing. Will check more but rough measurements look like release bearing is always touching the pressure plate fingers even with pedal up all the way.. Never noticed clutch slipping and still do not, but wonder if that could account for my issues. I did see the release bearing touching the fingers with pedal up peering in the side port but since there was no sign of clutch slip I thought it was ok. Maybe when I push the clutch pedal I am somehow making the fingers hit the clutch disc (bottoming out ?) despite adjusting the pedal stop so it is not much beyond release point.

[MV8]

With a hydraulic clutch system, the "height" adjustment of the slave is based on a new clutch where the bearing will be with one full stroke of the master used (I won't go into the more critical setup of the newer oem slave bearings with a green boot that are spring loaded).

 

When properly adjusted, the bearing can be pulled away from the PP fingers around 1/8 to 1/4". This clearance is necessary for the clutch to be self adjusting, since the PP fingers move away from the flywheel as the clutch wears/thins. The hydraulics take up the clearance and the bearing stays in contact with the PP fingers.

 

If this were a CAT converted from a cable with an external slave, the fork spring would be retained and the standard bearing used to maintain a gap needed to prevent premature bearing wear, but this is a SAAB system. Any internal slave will have a bearing that stays in contact with the PP fingers all the time since there is no way to add a return spring (plus constant contact is better in several ways).

 

In closing, if the replacement's height is too low, then the clutch would not release fully and cause grinding inside the transmission when trying to shift. If it is too high, then the clutch would have a shorter life, slipping sooner. 

Edited August 3 by MV8

[pethier]

I did a clutch master cylinder replacement on a Miata 1800 and I never touched the bleed screw.  I just pumped away. like mad on the clutch pedal until I finally felt the clutch action.  Clutch worked perfectly thereafter.  Not saying this would work with other cars, but it worked just fine in this instance.

[SENC]

Chris - I saw this morning that there is an active discussion on lotuselan.net on concentric slave use (and I know I've seen others there).  You might check that thread and others on that forum for additional guidance. 

 

https://lotuselan.net/forums/viewtopic.php?f=31&t=46138&view=unread&sid=00f39b24fa44b51a0f4f4399959b2ee9#unread

[Christopher smith]

Indeed that was a good place to go. Someone mentioned getting the dimensions wrong and self destruction due to pushing too far. I am checking the dimensions again but that may be it. When it was all together I noticed the release bearing was touching the pressure plate fingers but assumed it was ok since there is no provision for return on the Saab design concentric. Perhaps the newer release bearing I installed was thicker than the one I had used for years with no problem. Also, still not sure why that would be fine for up to 8-10 starts and then get noisy. Also, I did not see any mention of lubricating clutch splines but maybe I should?

[MV8]

Also, dry or binding at the pilot or warped clutch or pp can get hot and have a similar situ. I think you said you loosened the pp at one point during the initial slave R&R? Evenly loosened in a cross pattern at little at a time or did you loosen asymmetrically?

Edited August 4 by MV8

[Christopher smith]

Thanks guys- sure appreciate the good suggestions. Sure is a lot of stuff that can go wrong I guess. I expected lots of stuff to break back when I was racing but now even light duty is tricky- for me anyway. Actually I did not touch the pp or clutch disc when I replaced the master , slave and release bearings but also did not think to remeasure clearances. The pilot was lubricated but not the splines and  both measure fine, having an extra 5 mm depth for the input shaft and correct diameter for the pinto trans input shaft. PP sure looks fine and no unusual colors on old disc, pp face or flywheel. When I put in a new clutch and pp I would always go gradually in cross pattern and I will use blue Loctite. Anyone know the torque required off hand? I tried to pull the release bearing off of the slave by hand and it is stuck on, it spins fine but slight wobble and I think I see a tiny chunk of shiny metal shard in there so hope that replacing all that will fix the problem.

[slowdude]

6 hours ago, Christopher smith said:

  I did not touch the pp 

Sensible chuckle.

Edited August 4 by slowdude

[IamScotticus]

Dave Bean

 

Jake Lamont

Edited August 4 by IamScotticus

[Christopher smith]

Thanks for that info. I have that Bean catalog but had not seen the Formula Ford info. That 15 ft/lb seems right for the pressure plate ( clutch cover ) but wonder if blue Loctite means a bit higher maybe if it acts to lubricate the threads a bit before it sets up.  It took more to undo the bolts yesterday and I assume they had Loctite on them from 10 years ago. But of course that is no indication of the torque I should use for assembly. I was going to ask Ken at Bean Monday when I order more parts. I did note that the old release bearing was very tightly jammed on the slave cylinder (noted a bit of corrosion after only a year) and wonder if that was causing my release issues when hot.

[IamScotticus]

I think the even distribution of torque is more critical than bolt tension/clamp force. Like drive shaft flange bolts, the torque spec isn't high, It's the grade of the bolt that does the work.

I read five of my books on the clutch cover installation and didn't find any recommendation for Loctite on the pressure plate bolts, but at 15 lbs-ft, I doubt it would do any harm if not applied in excess. The most consistent advice is to tighten these down evenly In short steps so as to not warp the cover, AND keep the disc centered.

There was one reference to the use of spring washers.  These would be preferable to Loctite, I think.

I will PM you some book shots, I don't want to poke the copyright bear.

 

There is one very good point to remember on clutch discs..

The disc hub may have a high side at the center.  According to Haynes Escort Mexico& RS1600, the high side should face toward the flywheel, assuming there is enough relief in the FW center to allow for disc wear.  If it were reversed so the high side is toward the transmission, the spring fingers can foul on the hub?  Or is it the other way around, the hub will foul on the flywheel?  I suppose some measures are required.

I'm not an expert on this, just something to be aware of.  I'm surprised Haynes is the only book to mention it.  A clutch disc supplier mentions orientation direction on a disc installation instruction website, but they are general and the opposite orientation of the Haynes instruction.

None of the 1"x23 discs I got from Burton had instructions with them.

 

Going back and reading your problem,  you didn't have a problem before the slave change, but Im thinking the disc may have been incorrect beforehand.  It just managed to work with the older slave.  New parts tend to wear older parts quicker.  Perhaps the disc hub was eventually going to bottom out?  The new slave made it happen.  The face of the hub definitely shows signs of contact.  Nothing should be touching that face.

Just guessing.  You've checked everything else.

PM me for a new 7.5" 1x23 road disc and some shaft lube, if I can find it.  It hasn't been used for a long time. 

 

And what release bearing face do you have, flat, round? You have flat PP spring fingers.  They should have a round, or donut, bearing face contacting them.

 

Edited August 5 by IamScotticus