Quote:
Originally Posted by fz4k98
Over a couple years i tried aftermarket cmc and lines that were designed for the heat soak. Eventually i went back to all stock parts with high quality fluid and double wrapped the line from master to slave. The product i used was from heatshield products and called hot rod sleeve. For my situation, this gave best results.
The fluid is still susceptible to temperature swings as pedal is closer to floor on cold days but fine otherwise.
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Sorry if I'm grave-digging, but I wanted to kinda input my experience, as my car has gone through what appears to be it's FIFTH CMC... And no, I wish I was actually exaggerating; but I recently just put my 3rd CMC replacement in. The other 2 that failed were the original parts numbers that I posted in this topic thread (GM P/N #174-1179, AC Delco P/N #92067134), and the one that was replaced and came on my car when I got it, was GM P/N #92199594.
The same BS happened again, where my clutch pedal would start dying as I would be driving, and I'd be lucky if I had any clutch hydraulic pressure to disengage the clutch fully and get me home (without needing a tow). I even took your advice and sheathed my new stainless steel braided clutch line, with a fiberglass heat-resistant wrap. Just the SS clutch line alone actually made my clutch pedal feel good in general.
However, it seems to be a hit and miss, as some of my other CMC's have died in one go, and others take days to a week. And once again, there would be no clutch/brake fluid leaking anywhere, simply the seal(s) in the CMC failing (which I'd discover as I replaced the CMC through process of elimination). I also replaced my transmission fluid as well, and would notice the shifting quality decrease over the span of the first month into the next few months, after I replaced the CMC.
My latest CMC that I replaced, actually kept coming back to "normal", for the next few days, after the car would cool down. "Normal", meaning that you would think that air would get in and stay stuck; but no, the clutch engagement point was fine, and the clutch pedal would act like no air had ever gotten in. It wouldn't actually replicate the issue of letting air in, until the car would get up to operating temps (driving for 25-30+ mins or letting it idle during that time).
I got sick of going with OEM parts numbers and decided to take a chance on a Dorman CMC, P/N# CM640176. But as you know already, FTE and Sachs all supply parts for all the other companies that rebrand and sell/distribute the parts. I inspected the markings on the plastic composite CMC, and noticed the difference in maybe like 2 different things, with one being the time/date stamp of production, and some other production or serial number of some kind. Not sure what's even defective at this point, as it seems like my CSC is still obviously fine.
Now... with how weird my very last CMC acted, I decided to take it apart; which basically just included using a flathead to press in the main lock ring, for the plunger to the CMC assembly. Now, I noticed nothing out of the ordinary, except two things; one being that there was what appeared to be silicone lubricant stuck at the end of the CMC, and two being that that same lubricant was what came on the metal part of the plunger and it was now bone dry (which seemed typical).
I didn't initially think the dried out plunger was super important, however, the other spot that I noticed where silicone lubricant had gone, was around the main seal that the plunger used (separate from the main o-ring that is after the lock ring). I'm not sure if maybe the heat soak maybe softened the rubber(?) seal in the CMC chamber, and the combination of contamination with the silicone lube against the seal, maybe caused it to intermittently lose pressure. I was thinking this might be partially important to consider, since I have a remote/separate clutch fluid master cylinder reservoir, and I would notice remnants of what appeared to be clearish debris (resembling silicone) at the top of the reservoir and clutch fluid.
I cleaned the inside of the CMC out, as well as the seals, and then lubricated the metal shaft on the plunger with high temp grease. I actually planned to test the CMC I had put back together, out on another car. I'm kind of confident that it will work again; I just don't know if it will fail, is the issue. Although, I am sort of confident in my theories, this still doesn't give me any sort of comfort or reassurance whatsoever, for the available quality of parts for our mass produced, domestic American cars... Oh, and I was also too afraid to take apart my new Dormant CMC, to check the inside and maybe clean some of the silicone lubricant out..? If this current Dorman CMC goes out.... I'm gonna be at a loss of thoughts as to why. I'm also curious and probably won't ever find out, but I wonder when my bone stock CMC from the assembly line had actually failed...