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Stick Shift sticks in hot weather

In hot weather or even warm / humid weather, my very low mileage Mazda 626 (2002) becomes almost impossible to shift, especially from neutral to first, after about 20 minutes of driving. If I stop driving and the car cools off, it’s okay again, until another 20 minutes of driving. It’s fine in cool weather. This problem started in the summer of 2010.

Questions, on 2 topics:

Has the transmission oil been changed? How often, and when was the last one?

Does the clutch pedal feel the same as it always did? How far down do you have to press it before it starts to work?

Oh, and the 2002 Mazda 626 offered a 6 and 4 cylinder engine. Which one do you have? I’d like to assume the 4 with a manual, but I’d rather not assume.

The problem might be caused by a hydraulic clutch master cylinder being effected by heat.

The clutch master cylinder is mounted on the firewall under the hood. As the weather gets hotter the underhood temperatures increase. This increase in temperature can heat up the clutch master cylinder where the bore in the master cylinder increases in size. This then prevents the seals within the master from sealing properly to the bore and thereby no hydraulic pressure is produced to operate the clutch.

To determine if this is the problem, carry a large bottle of water in the vehicle. The next time it becomes difficult to shift into gear, open the hood and pour the bottle of water over the master cylinder to cool it down. If you can now shift gears with no problem, replace the clutch master cylinder.


It’s 6 cylinder. The clutch pedal feels exactly the same. Not sure about transmission oil change–perhaps I trust the dealer too much (?). I’m going to try Tester’s approach next time it gets hot. Thank you.

I think it’s the master cylinder too.
I’ve seen a brake master cylinder start to fail in the heat.

I would change the slave cylinder too. They’re not terribly expensive.

In the future change the clutch (and brake) fluid every 3 years.