Clutch Pedal/linkage problems of the 2004 Nissan Maxima

With my 2004 Nissan Maxima, when the clutch has heavy usage, for example in stop and go traffic, the clutch pedal goes down to the floor and stays there - I have no pressure and I cannot get the clutch in. After I pull to the side of the road, the clutch operation returns to normal after 10-15 minutes. This has occured 6-7 times (my car has 24,000+ miles on it) and from an internet search is being experienced by many frustrated Nissan drivers. Though it occurs intermittently it is often enough to have created several frightening situations for me in traffic, particularly on the highway and late at night. The dealer stated they are aware of the problem but aren't sure of the cause while the most reasonable explanations online point to engine heat affecting the master cylinder when the car is moving slowly. Nissan consumer affairs has been of limited help in helping us resolve this issue.

I've had a problem with my 04 Maxima almost from the beginning. Basic symptom has been if the car sits idling in traffic jam, or after a 3-4 stop and go local trips, I develop a lot of play in the clutch pedal. Normally, when I apply light pressure to the clutch pedal, I feel resistance immediately. When its acting up, I feel significantly less resistance in the pedal from the top, sometime almost half way through the pedal travel. If I continue driving it usually clears up on its own or if I park and leave it for 30+ minutes. Definitely seems heat related and does not appear in the winter. Despite the "slop" in the pedal, the clutch appears to be shifting ok and engages about mid pedal travel. Last month new symptom appeared. Twice, once after it was sitting at work all day and another time after returning from a 3 hour concert, the clutch pedal was all the way to the floor. I literally had to stand on it to get car into gear. Once, moving, it returned to normal operation after a couple of miles of driving. Originally took it to the Nissan dealer, but they could never reproduce the symptoms. At 30k, Nissan mechanic said it needed a new clutch without even looking at it. When to local shop. They replaced the master and slave cylinder and equalization valve without any improvement. They have never been able to reproduce the symptoms either. Two weeks ago, at 60k, I had them replace the clutch, pressure plate, throwout bearing and flywheel assembly. The pedal to the floor symptom has not returned (yet) but the clutch pedal problem is still there. Now I have a new problem which only started after they did this latest work. The stick is now popping out of gear which driving. Twice in 6th, but predominately in 5th. I left the car with the mechanic for a day and they could not get it to happen. They checked the linkage and bushings and they say everything looks ok. I went for a drive with them and of course it did not do it, until tonight.

Manual clutch failure. Driving in heavy, slow, traffic or for long distance and many hours of travel would cause the clutch peddle to sink to the floor making shifting nearly impossible. Problem occurred within first year of ownership. Stopping, touring car off and restarting usually fixed problem. Yesterday clutch sunk to floor and stayed there. Dealer examined car a year or more ago, while under warranty and could not find a problem. Now car is undrivable safely.