Cold weather can shrink seals around the plunger.

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Dear Car Talk: I have a 2013 Hyundai Accent with a six-speed manual transmission. When the temperature drops below 40 degrees overnight, the next morning, my clutch doesn’t respond properly. After starting and shifting into reverse, I can have my clutch to the floor and I still can’t shift out of gear or stop my car from moving backward. If I stop the car using the brakes, it kills the engine, just as if I had tried to stop with the clutch completely out. If after stalling I pump the clutch three or four times, the car runs perfectly for the rest of the day. I have only 2,000 (yes, two thousand) miles on the car. I’m 75 years old and have never owned a car, truck or motorcycle that I didn’t have to shift manually, so I know how to use a manual transmission. The service department at the Hyundai dealership where I purchased the car new can’t find the problem and correct it. Do you have any ideas? Thanks. — Hugh

A: Sure. Years ago, a customer came into the shop with a similar complaint. After running up his repair bill for a few hours, we finally discovered that he had two sets of floor mats in the car. Because they were bunching up behind the pedals, they prevented him from pushing the clutch all the way to the floor. So we tossed them in his trunk, charged him $300 and sent him away happy.

Not really. We only charged him $280.

Since you have so many years of experience driving stick shifts, Hugh, I’m going to guess that’s not your problem. But check.

If your floor mats are not guilty, and if you’re not actually leaking hydraulic fluid, I’d ask your dealer to swap out your clutch master cylinder. There may even be a technical service bulletin on it by now.

Clutch master cylinders often fail this way in cold weather. If the seals around the plunger are failing, they can shrink a little bit in cold weather and allow the hydraulic fluid to bypass the plunger. That creates insufficient pressure to disengage the clutch. Once everything warms up, the seals expand enough to do their job, and the clutch works fine again — until the next cold start.

Since you’re under warranty, I think you should politely insist that they replace the clutch master cylinder. They owe it to you to try something, and that’d be my first guess. Plus, it’s the cheapest thing for them to try.

If that doesn’t fix it, then unfortunately —for the dealer — the problem is the clutch itself, and they’ll owe you one of those, too.

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