'88 635CSi Clutch engagement

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spankey
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'88 635CSi Clutch engagement

Post by spankey »

I'm considering adding another BMW to the collection for a commuter car when I travel out of town, and wanted some input.

Background... I own and have rebuilt motors, replaced clutches, etc in my 85 M635 and my 88 M5, so not new to the games we play.

Looking at a 1988 635CSi... it's got 350k miles, however had a replacement Euro block installed at around 230- 250k miles. (new block has 100-120k on it).

There are a couple small rust issues on two of the fenders, however it's isolated to the fender only, and does not extend under the car.

Two owners ago, the car was a track car, and upgraded with larger 7 series brakes, Conforti chip, and a couple other things. It hauls .. really hauls.

Clutch- Supposedly the master and slave cylinders have both been either replaced or rebuilt, but the clutch pedal engages/disengages almost on the floor. It's not excessively stiff (my M5 did that as the pressure plate was failing). Clutch doesn't slip, and bites real well, just does that right on the floor. Any thoughts? Could this be some sort of upgraded clutch/feature that somebody would have wanted if they were tracking the car? I'm concerned about getting into an old used car, and finding a real nightmare.

Any advice or thoughts on this one guys? I'm a sucker for punishment, as I've rebuilt both of the other cars, but I'm trying to avoid that pain again. I simply don't have the time. Ohh yeah, the asking price is somewhere between $4000-4500.
bpoliakoff
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Re: '88 635CSi Clutch engagement

Post by bpoliakoff »

Check the pedal bracket for a crack
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.
spankey
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Re: '88 635CSi Clutch engagement

Post by spankey »

No luck finding any cracks on the bracket, unless they're known to hide really well.

I did hear there was some bronze replacement clutch bearings that people have said will help. Is there any truth to these? I believe this link is what they're referring to. Otherwise, I can't find any reason why this thing only engages at the floor.

https://www.iemotorsport.com/product/oi ... e46-z3-z4/

edit: Perhaps this is another potential offender.
https://www.ebay.com/itm/BMW-71-93-Clut ... 1283519248
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zinnocoupe
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Re: '88 635CSi Clutch engagement

Post by zinnocoupe »

Maybe the clutch just need to be bleed ? There always seems to be some one posting about problems when bleeding. I recently installed new clutch, slave , mater etc. I bleed the system a few times and it it seemed fine. I drove for a while and wasn't real happy with the pedal feel. One more long bleeding session and the pedal is now rock hard and way better feel.

Those bronze replacement bearings maybe a good idea but I just used the oem rubber bushings on my pedal box and they look like they'll last for 20 years. My originals were crumbling . The pedal shaft is now nice and firm. If you reach up into the pedal box and grab the pedal shaft and wiggle it you can tell if your bushings are shot by how much looseness you find. Either way I can't see those bushings making the pedal engage near the floor.
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
1977 530i Partially restored and running now!
1987 635csi 60K KM Garage Queen
spankey
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Re: '88 635CSi Clutch engagement

Post by spankey »

Thanks, that helps, I'm going to replace all the pedal bushings on both the M635 and the e28 M5.

Separately, that 635 I was interested in is from a friend, so I'm going to help him pull the tranny, and swap that fork lever pivot pin. We may separately bleed out the master. I'll try to report back with the results of our findings.
northNH
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Re: '88 635CSi Clutch engagement

Post by northNH »

FWIW I recently pulled the transmission on my (obviously expertly driven :wink: ) 180K mile ‘86 CSI to replace the just-started-feeling-crunchy original clutch pieces/parts.
Armed with everything I expected I would need, I found:

-broken throw-out bearing;
-reusable half-worn disk and strong intact pressure plate;
-perfectly smooth dry flywheel and perfectly good pilot bearing;
-no evidence of rear main seal or trans input or output shaft leaks;
-master and slave good as new, rubber hose the same.
The clutch fork and its plastic pivot pin were both totally without wear or damage.
And the pedal shaft bushings were tight as could be...

The ONLY thing that needed attention or replacement was the throw-out bearing.
Remarkable.
'86 635 5spd 175K Blk/blk orig paint/int
‘88 M6 24K time capsule Black/gray
'92 MBz 300CE Sportlined 175K Blk/wine orig paint/int
‘94 MBz E320 wagon
'62 Volvo Amazon 65K mile time capsule

One lucky guy...
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zinnocoupe
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Re: '88 635CSi Clutch engagement

Post by zinnocoupe »

spankey wrote: Fri Apr 23, 2021 12:58 pm Thanks, that helps, I'm going to replace all the pedal bushings on both the M635 and the e28 M5.

Separately, that 635 I was interested in is from a friend, so I'm going to help him pull the tranny, and swap that fork lever pivot pin. We may separately bleed out the master. I'll try to report back with the results of our findings.
I would certainly recommend bleeding the slave and master BEFORE removing the transmission to check that pivot pin. You could same yourself a lot of extra work if it is just some air in the system. Good luck
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
1977 530i Partially restored and running now!
1987 635csi 60K KM Garage Queen
spankey
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Re: '88 635CSi Clutch engagement

Post by spankey »

Just wanted to follow up with this to report back on the solution.

Recap... Clutch was not engaging until almost the floor. Finally, it got to the point where no matter how hard the clutch pedal was pressed into the floor, it wouldn't actuate the clutch.

The problem was the Clutch pivot pin. The plastic was completely broken down, probably from heat. The pin was replaced with a bronze one, and the whole clutch, pressure plate, and flywheel was replaced/re-faced. Clutch function is good now, solid engagement, no issues. Feels even better than my '85 M635 clutch.

This was the type of part we used for the fix:
https://www.ebay.com/itm/BMW-71-93-Clut ... 1283519248

Thanks for the help all--
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hornhospital
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Re: '88 635CSi Clutch engagement

Post by hornhospital »

Thank you for the follow up. Too many threads turn out "open ended" with no solution.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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