Clutch pedal issue. 2005 Max with 18,000 miles. Hot day today. Drove with A/C on. Mostly stop and go driving. Clutch pedal lost 50% of its pressure. Total clutch travel was cut in half. Had to put my foot under the pedal to pull it back up. Full engagement occurred one inch off the floor. Turned A/C off. Clutch returned to normal within 30 seconds. Turned A/C on, clutch lost pressure. Turned A/C off. Clutch returned to normal. Drove like this for over an hour. As long as A/C was off, clutch was fine.

Stopped by local Nissan dealer on way home. Spoke with technician for a minute. Tech said he never heard of anything like this. He had a second, walked out to the parking lot and looked under the hood for leaks. Saw nothing, but said leaks could hide easily. Clutch fluid reservoir was full to the MAX fill level. Even with a leak, mechanic had no clue why symptoms were correlated with A/C. Appointment set for early next week. Any of you mechanics have a theory?

 

I have had a clutch problem like this but I didnt associate it with the AC. I have had it happen 3 times to me, all under differing circumstances. Im equally baffled.

 

This is very baffling. Your symptoms sound like you lost clutch hydraulic pressure (from a leak). Yet when you turn off the A/C, the pressure returns. Must have something to do with the heat from the A/C causing the fluid to become thinner and bypass the clutch master cylinder. That is my best guess -- hope the dealer can find the problem. Let us know what happens.

 

Concerned about safety, I stopped by the dealership again to talk to one of the Master Techs. He had no answer, but like SilverMax wrote, he suspects the A/C compressor added heat to the system.

Mentioned the problem to a friend who happens to owns a large motorhome. He said this resembles a problem they sometimes get with their brakes on hot days. If their brake systems get too hot, they can boil the brake fluid. Or, if water happens to be in the system, the water boils. Once the water, or fluid, turns to gas, it compresses and the system can lose pressure. I checked the fluid in my reservoir and it didn't appear or smell burnt. But what do it I know?

Earliest I can get the car in the shop is next Wednesday. I hope they can diagnose it.

 

same thing happened to me 2 weeks ago; really hot day, lots of city driving. parked the car and everything returned to normal the next day. hasn't happened since luckily.

 

I'd bleed the clutch. It's a two person job, but easy enough to do at home with simple tools.

I'd guess you either have air or moisture in the lines. In either case heat could trigger the symptoms you're describing.

 

I have the same problem. Lots of road construction in the St louis area and when I get in stop and go with the air on when it is hot my clutch pedal does the same thing. I changed the fluid and bleed it and it still does it. Pisses me off!!! I was gonna post something but someone beat me to it. It has happened abot a dozen times and it returns to normal as soon as the car cools off or I get out of stop and go! Weird!! Acts like the fluid breaks down and loses its viscosity but I put new stuff in it. Fluid level always stays the same and it doesn't leak!! I thought I was the only one!!

 

Yeah, ive had similar problems on few occasions and Id guess that theres a small amount of air in the lines. Weird about the a/c though.

 

I had the same thing happen several times. I went to the dealership after it happened the last time because it happened not when I was driveing but after the car had been siting for about half an hour they replaced the clutch master cylinder and I have hot had it happen again. The mechanic thought it was a seal on the piston in the master cylinder leaking internaly when the pedal was pushed.

 

That explanation makes sense and this leaking seal tends to leak more (internally) when the seal and the fluid gets hot (like from running the A/C on a hot day).

 

I had this happen to me yesterday leaving from work on my break. I drove about 25 miles to work with the a/c on the whole way... 102 degrees here yesterday! Anyhow, I parked the max, came out 4 hours later, went to push the clutch in to start and no compression??? I got the max started, pumped the clutch a few times, got a little compression back. At first, I couldn't even get it to go back in gear, eventually it went in... but it would fully engage within like an inch of clutch release. Also, the a/c was still running. I drove it like that for about 2 blocks, a/c still runnin, and it returned to normal. Did anyone figure out for sure what causes this to happen?? Def the clutch master cylinder seal?