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Car: 2010 Mazda 3 2.5L, Manual Transmission, 163000 kms.

My clutch pedal feels sticky when the outside temperature is low(below -10C). By sticky, I mean it requires a bit more effort to push it in and it takes longer than normal for the pedal to rise when I take the foot off the pedal. The pedal feels normal after about 10 minutes of driving.

I have had the transmission fluid changed when I bought the car in April, 2017. No other maintenance was done to any transmission components. This is my first winter with a manual car.

Is this behaviour normal in cold weather or is there something wrong with my car?

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  • Are you using winterized oil? Oil thickens as it gets colder, so that might cause the "sticking" that you've noticed, since it'd make the movement of the moving parts more difficult. – nick012000 Dec 22 '17 at 23:12
  • @nick012000 Which oil are you referring to? – rana Dec 27 '17 at 7:00
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At that temperature I would be more concerned about the viscosity of the grease in the clutch disc splines, rather than the brake "hydraulic" fluid.

Maintenance of this fluid is cheap and easy, however, and makes a great starting point to either confirm or eliminate that part of the clutch system as a culprit.

Re-greasing input shaft splines is quite a bit more involved.

ON EDIT:

You also might try and vigorously work the clutch pedal with the engine off. Does this change the feel after a few minutes of pumping? Also, how do the gear changes feel at that temperature? Does it seem like somebody put syrup or peanut butter in the transmission instead of the normal "summer" feel?

My '76 FJ40 clutched and shifted like it was under water when the temperature was very low, but that was a long time ago at -5 to -15 Fahrenheit, with primitive single viscosity lubricant. -10 C doesn't strike me as particularly cold, but the feeling is subjective - and the "clutch effort" perception you are sensitive to might not be a problem; just a keen observation.

You could gently heat the clutch master cylinder (no flames, something like a hair dryer) and see if that makes an immediate improvement. Or better yet, just replace the fluid completely (bleed if possible) and see if that makes an improvement. The latter approach accomplishes maintenance you need to do anyway - especially if the fluid is original at 163K.

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  • Thanks for the suggestion. This does not sound like an easy fix. I'm guessing I have to pull the transmission out just like when you replace the clutch. – rana Jan 8 '18 at 16:31
  • Yes... unfortunately. However, @Myself has a very reasonable idea, and I would replace the clutch "hydraulic" fluid (usually brake fluid, unless you are unlucky enough to have a Citroen). This is maintenance that needs to be done anyway, takes fairly little time, effort, and money ... and you might find out that was the culprit all along. That "brake" fluid is just as hygroscopic (affinity for absorbing moisture) as when the identical fluid is used in an actual brake circuit. For some reason it is often overlooked. Let's hope I'm wrong - but it's a great starting point in any case. – SteveRacer Jan 9 '18 at 2:33
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IMHO it is not normal: The clutch is supposed to spring up directly when you release it.

I can think about the following potential root causes:

  1. (Provided your car has an hydraulic clutch actuator) The brake fluid in the clutch actuator lines needs to be replaced (Often overlooked as it is a separate circuit). I would advise you to perform this as it is quite cheap and a leaking slave cylinder is your worst nightmare..
  2. Some component of the clutch mechanism degraded so that it is susceptible to cold-stiffening (clutch pedal, master- or slave cylinder). Perhaps it is time to lubricate the clutch pedal linkage?
  3. This is the normal behavior of the car.
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Hydraulic fluid will get less fluid with decreasing temperature. This is completely normal.

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