Clutch Cylinder Question

This is for a 2016 Hyundai Veloster Turbo with 6 speed manual and close to 70K miles.

As of two weeks ago I noticed the clutch pedal getting soft to the point of making shifts very difficult until you pump it. This usually happens after cruising at 70 MPH or higher for 10-20 minutes. So I guess it has to have something with the fluid getting warm.
For this car, the slave is in the transmission housing. Brake and clutch fluid reservoirs are shared.

I bled the system and it felt better for a week, but it might had been due to the car cooling down too. I am not loosing any fluid, nor is there a visible leak.

Hyundai dealer could not reproduce the problem after driving it around, I assume to run errands for 20 miles.

Neither Hyundai nor the dealers would tell me if this is covered under the 100 K mile warranty. They have to take it out to tell me, but their labor rate is $175/hr.
I guess my question is about the proper bleeding of the system. The bleeding valve is before the transmission housing and before the slave cylinder, so when I bleed the clutch, is any fluid from the slave cylinder being refreshed?
The clutch itself seems solid, no slipping/etc.
Not sure if anyone has experience with the Hyundai warranty on these parts.
Any other suggestion is also welcome, as it seems like I either have to pay someone to change both cylinders or make a reservation for a tow truck pretty soon.

It sounds like the clutch master cylinder is leaking internally once it gets hot from engine heat.

This is how the clutch hydraulic system is bled.

I wouldn’t worry if the fluid in the slave cylinder is being refreshed.

I would worry more about replacing the master cylinder before the clutch is damaged.


Thanks @Tester
I have already bled it once.
The reason I think it is the slave is that continuous high speed driving is making this failure to show up. During that, the master is not doing anything but I am thinking the slave is getting heated up in the transmission housing.
I think I can change the master myself. Parts are out of stock everywhere, so have to order it from the dealer.

If the slave cylinder were leaking, there would be hydraulic fluid on the ground.

The master cylinder creates the hydraulic pressure, not the slave cylinder.


I’ve had the slave cylinder fail in my truck twice over the course of 300k miles. Both times it just fails suddenly, total loss of pressure and fluid squirting out. You should just leave yours alone and concentrate on the master cylinder, unless hyundai will replace both under warranty. They probably won’t.

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I almost got stuck today. So, back to the dealer. The master tech feels it is the slave because it acts up with steady high speed driving (the slave is in the transmission housing). The slave is covered under warranty but not the master. I have ordered the mast myself but waiting for the slave to arrive for the dealer to change it.
I might change the master myself and see, as I’m not that keen in them tearing into the transmission. It is a full day job where stuff can go wrong/brake/etc.

There are no clutch hydraulic parts listed as covered parts in the warranty book;

Case and all internal parts, axle shafts (front/rear), constant
velocity joints, front/rear hub bearings, propeller shafts, seals
and gaskets, torque converter and converter housing and
clutch cover and housing, transfer case for Santa Fe, Tucson
and rear differential for Santa Fe, Tucson and Genesis.

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Thanks for that list. Seems like the clutch referred to here might be the dual clutch?
Not sure, but the manager said the slave is covered, the master not. Hoping it is correct, otherwise their labor rates is high and I would rather deal with an independent shop.

If he said it’s covered, I’m sure they’ll cover it.
Let them change it, and see what happens.
Let us know.

If the system is under warranty, I would not touch any part of the system until the warranty work is done. You are very lucky it is under warranty. Anything you do (such as master cylinder and bleeding) can void the warranty, even if done perfectly. Just leave the whole problem in their hands.

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Here is the update.

The clutch issue got worse. It would be fine when cold, or when pumped ten times, but then after a 15 min drive at 60 MPH the pedal would completely sink to the floor. Went back to the dealership after I almost stalled on the exit ramp. They decided that it was the slave cylinder, it was covered under warranty.

It was changed, have picked up the car, doesn’t exactly feel like new and haven’t had a chance to take it on the open road with a steady speed to see what heat does to it.

The problem is, to change the slave cylinder on this car, the transmission has to be dropped (slave is in the housing). When I check the engine bay, I do not see traces of work that would imply this was done. From the front wheel torque (over tight), I can tell the wheels were taken off. But seems like nobody touched the batter, wiring, etc.

So, I have my doubts even though I am glad it was warrantied. Will keep you guys posted as I keep driving.

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The symptoms to me sound more like the problem is the clutch master cylinder. I had to change that part on my Corolla at around 80 k, and again at about 160K. Never had to change the slave. Slave cylinders are a more simple design than the master. That’s why they risked designing the slave into the inside of the trans, thinking it unlikely to have to remove the trans to replace the slave. The idea is that in most cases the slave would only be replaced when the clutch was replaced. The master is the more complicated gadget, therefore more likely to fail, so they made it easy to replace.

If warranty wasn’t an issue then the common sense approach would be – imo-- to change the master, bleed the system, and see if that fixed it. If not, only then would the slave be considered. But since the warranty is still in effect, best bet is to let the dealership figure it out for themselves I guess. Sort of a frustrating situation.

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The dealership probably just bled your system to see if that would cure things. Time will tell.
The slave cylinder inside the bell housing is an idiotic design. My Ford Ranger needed a replacement at 125K when the clutch was fine. Even if the design lasts longer than an external slave, the tremendous labor costs make the design very silly.


@George_San_Jose1 Agree, I had already ordered the master to change it myself but when they offered to change the slave under warranty, I didn’t pick the part and didn’t touch anything not to void warranty. But now I guess we can tell it is not the master.

The car is mostly fine now after around 200 miles. But I also feel that the just bled the system. OTOH, I am sure they took the tires off which doesn’t make sense.

Doesn’t the invoice list parts and labor? Not labor hours per se but a labor operation number.

No. It just says states my complaint, that inspection found the slave cylinder to be leaking. Part # replaced, parts and labor 0/NA.

That is part that was replaced, the customer doesn’t need to know the cost of the part.

Maybe they know a shortcut way to just pull the transmission back some instead of taking it all the way out.

Maybe the old master cylinder is a bit tired too.
Put the new one in and it may feel better.

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I am sure after 70K miles the master is a bit tired. I was ready to swap it out until the warranty coverage issue rose. Right now it seems ok, so am going to wait and see. Willing to pay them to do the master instead of DIY just in case the slave wasn’t changed and causes issues.
On this Hyundai topic, having the 100K mile warranty is nice but I would rather have a car that doesn’t need the warranty work at all.