So I got another weird issue for the community to mull over:

For the last, I would say year, very intermittently my clutch pedal would feel more like I'm pressing down on a sponge, then what I would consider regular pressure. However, the clutch does return fairly quickly back to its original height when released. I've already had my TOB, pipe, and master cylinder replaced, and had it flushed twice by dealerships. Nothing is leaking, and this only happens mostly when it's really hot outside.

For the engagement of the clutch when I don't have an issue, normally I have about 2 inches of dead space before I can feel the clutch press down onto the fluid and a couple more inches when I can glide through the gears.

When I do have the issue, same dead space of 2 inches, then super spongy and the engagement of the clutch doesn't happen until I'm very near the floor. When it gets really bad, I have to stand on it to engage, and somewhat carefully guide into gear without grinding.

It's a hydrolic or something issue as when I turn the car off, I can flip through gears like butter.

Which leads me to question: the TOB was done about 3 years ago, everything else near the beginning of the year. Could it be the TOB again, or should I upgrade to DOT 4 brake fluid?

 

It could be the tob or possibly the master, but I had a similar issue once years ago from the seal on the pipe. No obvious fluid leaks/level drops were noticed, but it started to suck air and bleed the pedal down. Showed up most often when I would cruise in 5th down the interstate for extended time, or if the car just sat too long. Normal driving I was always pumping the pedal enough it seemed to act fine.

I just swapped the seal out, and it's been good since.

Edit: I've had DOT4 fluid since I first bought the car and flushed everything. It might help, but I can't say 100% that it'll be the answer.

 

Definitely sounds plausible, how hard is it to access the pipe to change that out?

 

It's a bit of a pain but not too bad. Technically, the trans is supposed to be removed to replace it. Easiest way for access is to pull the PCM and fuse box up, and it'll be right underneath.

If you're careful not to bend the pipe, you can pull the seal off of it, and swap the seal off a new pipe. I was almost about to pull the trans to do the tob again, but tried this and that was my issue. Idk if I had nicked it when installing the bleeder block originally, or if there was just a defect that finally presented itself after being installed for a bit.

 

ZZP has the entire pipe for $14 + shipping so I might just swap it out completely. My problem is doing the bleeding afterwards as I'm sure I'll lose a bit of fluid; on top of that, to replace the fluid with DOT 4 for better heat dissipation.

 

@Tdubbs Looking at the parts, I'm thinking about ordering a new elbow and line all together - doing the clutch pipe itself would be outside of my area of work as I don't have a way to drop the transmission out from under the car safely. Was it the elbow itself to the clutch pipe that you had issues with, or with it the line to the elbow?

Here's the ZZP product for what I'm thinking of replacing.

Quick diagram:

 

I had issue with the seal on the clutch pipe itself, where it meets the clutch elbow.

I replaced the elbow when I replaced the master(braided line as well), thinking the master was it, but it still presented the same symptom. That's when I had the random idea to just swap that seal, because my next step was to drop the trans thinking the tob had went.

 

This was my logical conclusion, I'm grateful for the confirmation. Ordering some parts; I should make a video for this since I found only 2 that even talked about it.

 

I just had to replace t.o.b. for my 08 Chevy Cobalt SS. (Catastrophic failure after 40,000 miles). I replaced clutch pipe & t.o.b.. That clutch pipe seal is a real p.i.t.a. to get right. For me, I had it connected right, however, when I went to open & close the bleeder screw on the distribution block to bleed the clutch it would cause the seal to move then leak. Sooooo. I had to put a back up on the distribution block to keep it flat in order to not move the clutch pipe seal. This worked. End
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I mentioned this in other threads, but if somebody runs into this issue, it was replacing the clutch line and the elbow that resolved the issue. Luckily I didn't need to replace the pipe going into the transmission. It'll take a couple hours but if you take your time, you can absolutely do it in your driveway. Just remember to bleed the system and check for leaks.

 

Curious;
Was the line cracked or broken in any way?

I am wondering if the issue wasn't the line, but the connection from the line into bleeder valve (looks like the diagram call is a 'clutch elbow').

I wasn't going to reply because I saw the discussion was from last July, but my gut was saying you either had a bad TOB, or you had (or were getting) air in the system.

 

No external damage that I could find it either the line or the elbow, it must have been the gaskets inside just seeping air enough but not large enough to cause a leak.