What the heck is up with the hydraulics?

Tell me if this makes any sense to you guys because it certainly doesn't to me.
So I've had my baby; a 2010 Jetta Sportwagen TDI I4 2.0L with ~98,000 miles on the odometer, for a few months now and I've had the non-stop problem of the clutch suddenly and seemingly randomly acting up by sticking and/or not springing back from the floor. I had changed the clutch master cylinder and then over time bled the system several times but any time I managed to get it working reliably it'd randomly act up again.

However it is important to mention that the brake hydraulics I've never had a problem with, but I recently changed the front brake pads which were nearly worn out and, while replacing them, I of course pushed back the caliper piston.

So now for the real puzzling part:
Last night I was doing routine maintenance during which I changed the oil* before heading to Wally world and I noticed the clutch felt firmer than ever before and the whole trip (about 30 miles worth counting both ways) the clutch pedal remained firm and never got sticky or stayed on the floor like it had before but to be sure I checked it a couple of hours after I got home and this morning I drove it to go and get breakfast and sure enough, to my amazement, the clutch pedal was still working amazingly.

The oil that I drained out was very thick and very black and the old oil filter didn't look to be in too good of a condition, so my theory, if it is related, that the old black syrupy oil, which I have no idea when it was last changed by previous owner, was somehow affecting the vacuum pump degrading the performance of the hydraulics.


Is this a mere coincidence or could changing the engine oil somehow improve the hydraulics? Any thoughts?

* I used a new OEM oil filter from vwpartsvortex and the TOTAL Quartz INEO Long Life sythentic 5w30 diesel oil approved by VW

It's mere coincidence. The oil will always be quite black at changes.

I am going with coincidence as well.
I am trying to think of some way that the angle of the car, during the oil change, could have allowed the clutch cylinder to bleed. It's my current guess.

I was thinking air in the clutch circuit also. The possible steep incline causing the air to bleed out didn't occur to me. Sounds quite plausible.

Ah, no. make sure your reservoir level is all the way up to the tippy top. Anything less than say 1 inch low will put air into the clutch circuit.

Unless vw really changed some things, your clutch is not vacuum assisted so the two are completely unrelated. Likely, what happened was that in compressing your calipers, you refilled the shared reservoir and gave your clutch master the fluid it needed to properly operate the slave cylinder.

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congrats on the new car.

you might want to change the brake fluid.

it is probably due.

http://pics.tdiclub.com/data/516/2010_All.pdf if you do not have the original owners manual and maint schedule.

He said he changed the master cylinder. I would assume that entailed adding new brake fluid.