Heavy Clutch Issue

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bobinyelm
Posts: 11
Joined: Wed May 03, 2017 4:41 am
Location: Olympia, WA

Heavy Clutch Issue

Post by bobinyelm »

1986 635CSi 236k miles 5spd Manual

I purchased my latest e24 last year (after foolishly selling a really nice 633CSi and an e24 B9 Alpina some years ago-acts I've regretted for 20 years) and among the "to-dos" on my "new" e24 was a clutch job because the clutch force needed at the pedal was very heavy (though the clutch was very smooth and responsive), as in the past with my e28/e24 BMWs clutch force increased with age, so I figured the pressure plate was fatiguing.

I recently pulled my transmission, and after cleaning (steam parts-washer cabinet), examining all of the internal release hardware, and putting new input and output shaft seals, I replaced it in the car with a new LUK clutch kit (Clutch plate, pressure plate, pilot and release bearings), as LUK is OEM and always resulted in a nice "easy" and smooth clutch. Strangely, it came with a Sachs stamped disc, but whatever.

Much to my consternation, the NEW clutch takes the same high pedal pressure to depress as the old clutch assembly!

I regularly drive a variety of e28s that use the same "everything" and NONE are as heavy, and have owned a large number of e9/e12/e23/e24/e20/e32 manuals (including an e23 B9 Alpina in addition to my old e24 B9), and I currently own an e32 5 speed manual 7 Series, which is light as a feather clutch at 230,000mi on the clock. I mention this only to show I have driven enough to know what doesn't feel "normal."

There is not "friction" feel to the clutch. It is smooth, springy (meaning no stickiness to the pedal action), and is as smooth on take up and release as the old one (which had maybe 1mm friction lining before the rivets would have been level with the lining).

I have driven a large variety of manual transmissions in other vehicles in my 55 years of driving, and this one is probably in the top 5% for clutch pressure necessary to release. Virtually ALL of the others were VASTLY improved upon installing a new disc/pressure plate. Even my Dodge Cummins 1 ton dually pick-up 6 speed takes only about 50% of the force needed for the e24, in fact (I installed its LUK clutch about 20k miles ago).

I am perplexed, and wonder if anyone else has encountered this? I read the search results for "Hard Clutch" and "Heavy Clutch" I did on this site, and most everyone reported vast improvement with a new clutch kit, as one would expect, and I have to wonder what's up with mine.

I bought a new slave cylinder, but didn't install it yet (I needed my lift for another job and didn't want to take the time to bleed it), but there are no leaks, and the "action" of the old cylinders is very smooth, so I tend not to suspect/blame the hydraulics. I lubed all of the contact points in the bell housing with some anti-seize, and they operated perfectly smoothly, and the new release bearing slid smoothly on its guide tube.

The transmission shifts perfectly, and as I said, the take-up and release are very smooth with no dragging, or juddering at all. The ONLY complaint is the force needed to operate the clutch pedal.

I am perplexed (and disappointed) as the heavy clutch detracts from my driving pleasure, and is out-of-character for the car. I figure if my 1 ton dually clutch controlling 600+ ft pounds of engine torque is as light as a Toyota Corolla clutch, why can't my Coupe be as sweet? This cannot be "right."

Opinions/suggestions?
Bob

Interestingly, when I drained the transmission prior to removal, the fluid was neither gear oil, nor auto trans fluid, but rather was as thin as water. Turns out it was parts washer solvent! Smelled like Stoddard Solvent as used in the aviation industry (I am an FAA aircraft tech so recognized the smell immediately). I called the fellow who sold me the car 18mo ago and he said in his 2 year ownership he never opened the transmission, and that it was his understanding (backed up by an inch of receipts) that the car was only serviced by its only other owner by dealerships. The only thing I could figure is that a tech was flushing the trans and forgot to drain the solvent and install gear oil! There appear to be no ill-effects of the solvent, as the synchros and shifting effort (gearshift movement) were and are perfectly normal (I did replace the shift control "T" for less play). The drain bolt DID have ferrous metal filings on it, but no apparent operational problems. I did a fill/drain/refill using 75-90 Marine GL4 gear oil (not easy to locate non-GL5 synthetic fluid that I could see) to get out any remaining solvent effects. I would have guessed that 10,000-20,000mi of using only parts washing solvent in a transmission would have caused terminal problems!
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