I test drove a car today that had an interesting and potentially dangerous clutch problem.
The first thing I noticed was, when I pushed the pedal in it felt kind of odd, like at some point it went past center and got easier, almost like it was on an eccentric. But the second I was out of earshot of the dealer I put my foot in, ran it up to redline and shifted but the clutch was slow to re-engage and it revved to the moon. It did this on every shift. If you drove it normally it seemed fine, but that's not how I drive. Thinking maybe the car had been sitting a long time, I decided to pump it a few times to see if maybe something would free up. On the third pump the it stopped about halfway down like I was pushing the brake pedal, and the clutch would not do anything. I drove the car about 20 minutes and was able to duplicate it every single time. When I returned it to the lot, I got the salesman to hop in and try the clutch and he got exactly the same thing. It was OK in that it gave me an easy out. I had no intention of buying the car, I just went there because it was close and I wanted to drive one to see if I liked it. I've been driving manual trans cars all my life and never seen this happen.
Master? Slave cylinder, or something in the linkage?
It was a 2016 Chevy Spark. And I liked it.
The typical clutch pedal spring design provides some resistance initially, then there's a transition, and past that, it actually helps you hold the clutch pedal down. That's why the pedal won't come off the floor if there's a bunch of air in the hydraulic system. The spring is holding it down. I think that's what you might have been feeling at first. The rest, I have no idea.
Clutch would not DISengage?
Normally what you describe with the slippage and ability to "pump up" the clutch sounds like a binding throwout bearing or release fork pivot, which is really common on Subarus (both issues, depending on pull or push type) and also Hyundais. But that leads to a failure to ENgage, due to slippage or in extreme cases being completely stuck disengaged (no friction)
I would have thought a modern GM would have an annular slave cylinder, which avoids all those problems...
It was slow to re-engage the FW with the transmission. I thought maybe the fork was sticking, and pumping it a bunch might free it up. That's what I meant by linkage but I was having a senior moment
Is it a new car? If so, that's pretty normal, because it's designed for idiots. And if it's a GM product, they have the most horrible feeling clutches in the world, so...
It may have a clutch delay valve. Later s2k's had this and it was pretty much universally hated. It basically just slows down the rate of re-engagement to (in theory) smooth out shifting and protect other drivetrain parts from shock.
My son's Xterra did this. It was a missing pivot bushing the changed the geometry on the linkage and spring just enough that you would occasionally need to pull the pedal up to get it off the floor.
In reply to freetors :
That was my first thought but it was really bad. Then it pumped up on me, so I wondered if they may be related.
Streetwiseguy said:
Is it a new car? If so, that's pretty normal, because it's designed for idiots. And if it's a GM product, they have the most horrible feeling clutches in the world, so...
Well... I drove another, exact same year and model today, no issues whatsoever. It shifted fine, no funny over the center pedal feeling, no pump up and no slippage on the upshift. The owner looked at me a little funny when I did an abrupt upshift and got on the gas hard, but I explained it to him and he was good with it.
Any more ideas?
Oh, and I've been dailying a GM with a manual trans since 1992. They feel ok to me.
Is the tob sticking to the input shaft?
Wrong grease or something getting in there and not physically letting the TOB return normally?
