Hi, and thanks in advance for any help you can offer. The clutch pedal on my 2004 Nissan Maxima SE (80K miles), over the course of dozens of depressions in very heavy stop and go traffic yesterday, gradually went to the floor, finally making it all but impossible to shift. After scraping through a few gears, we got onto open hiway about 5 minutes after the problem began. Tried pumping the clutch by lifting it with my toe, but it just remained limply on the floor and would not firm up. We’d been in traffic for nearly an hour.
About a block from my house --and after about 10 minutes of driving on open road-- the pedal quickly firmed back up, feeling tight, fit and new as could be.
This had happened a couple times before: once at about 40K miles and then again about 60K miles and, near as I can recall, it had been idling for a long time just before the problem 60K mile incident.
I’ve researched the problem on the net and there appear to be a number of '04 Maximas experiencing this same malady. Some feel the symptoms reflect the transmission fluid overheating and losing it’s hydralic “functionality.” Others speculate that the the master cylinder is going bad. If so, however, there seems to be no reasonable way for a non-mechanic (myself) to confirm that the MC is bad. I have an insurance policy that would pay for a bad master cylinder, but of course the dealer tells me they “can’t fix what they can’t see…”
I’m stumped… Have any ideas what may be happening or how to pinpoint the problem? Thanks again!
The master cylinder is probably being heat effected.
The master cylinder sits under the hood where all the engine heat is. When driving, enough air passes through the engine compartment to remove the engine heat. When moving slowly or not at all, the engine heat accumulates under the hood and starts heating up the master cylinder. As the master cylinder heats up, the bore in the master cylinder expands. At the same time the cup seal in the master cylinder shrinks because rubber shrinks when it’s exposed to heat. This results with hydraulic fluid bypassing the cup seal where hydraulic pressure can no longer be produced to operate the clutch. Once you start moving down the road again, the heat is removed from the engine compartment and the master cylinder cools back down. The bore in the master cylinder shrinks back down and the cup seal expands, and hydraulic pressure is restored to where the clutch functions again.
Tester
Thanks Tester!
Your theory sounds eminently reasonable. And so, if I choose to accept it as fact, is there anything that I can or should do about it? (Other than just staying out of traffic jams… 
Maxima04
Replace the master cylinder.
Tester
Okay, thanks. One final piece of the puzzle, will there be any evidence available to prove to the insurance company that the m/c is malfunctioning and needs replacement?
Maxima04
What I would do is, drive the vehicle to the place of repair. But make sure the engine is hot enough to cause the failure. Leave the engine idling, and get one of the mechanics to come out and step on the clutch pedal to see that’s there’s no hydraulic pressure. Then shut the engine off, open the hood to let the heat out, and wait for the master cylinder to cool down where it functions it functions again. That should be enough to prove that the master cylinder is faulty.
Tester
Thanks again for all your kind help, Tester.
You’ve been great!
Maxima04
You could show them Testers post. Let us know what they say:)
Thanks for your suggestion, oldschool, I had been thinking about doing just that! I’ve got it printed and will talk to them in a few days. I will post the results after we talk.
Best,
Maxima04
As a test why don’t you wrap the master cylinder in heat reflective aluminum foil?
I agree that the clutch master cylinder is the likely cause and if the master cylinder is replaced it would be a good idea to replace the clutch slave cylinder at the same time and flush the old fluid out.
The reason for replacing the slave cylinder is that is it quite possible the master could be replaced and the slave will fail the next week or month leaving you right back in the same predicament.
Speaking of old fluid, it’s also possible the fluid could be badly contaminated due to age and is either the cause of the problem or the contributor to a failing master or slave cylinder.
This issue it not difficult to diagnose and solve. If the dealer can’t figure this out they’re either clueless or simply trying to brush you off.
We have the same program as described above with our 2004 Nissan Maxima. It started at 11,000 miles and has continued through 24,000 miles today. Our question is: How will replacing the master cylinder correct the problem (considering that the “old” one is not worn out)? Wouldn’t we experience the same problem since there seems to be a manufacturing/engineering defect?