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Help! put gear oil in clutch fluid reservoir

Manual Transmission, 2000 Hyundai Elantra GLS:

Reservoir was dry and I was having trouble getting in gear. By mistake I put about 1/4 cup of gear oil into the clutch fluid reservoir! The car sat overnight and I only drove it back and forth in the driveway before it dawned on me that I had put the wrong thing in there. I took one of those sponge bottle scrubbers and soaked up the oil and then took long cotton q tips and tried to get the rest of the oil out. Before that I called a mechanic and he said any oil in the line would make the rubber swell. He was talking what sounded like major stuff. If I only put a small amount in the reservoir is there anything I can do to divert major problems? What should I do? Have I destroyed the clutch, the transmission? I’m so mad at myself.

The hydralic clutch is very similar to hydralic brakes, most often using the same type of fluid. Since you moved the car and used the clutch to do so you have moved the gear oil from the reservoir into the lines and perhaps down to the slave cylinder at the other end.

I’d get the car to a mechanic and have them flush all the old fluid out and replace it with the proper fluid as per Hyundai spec. The longer you wait to more chance of damage. If you get this done right away I think you’ll avoid any long term problems.

You don’t want to use the clutch until you get new fluid in there, so that could mean a tow to the mechanic.

Uncle Turbo! Thank you so much for your fast reply. The car is being towed to the shop as I type this.

Great way to start the weeK! Hopefully the report from the shop will be that all is well and the rest of the week will be better for you.

All that needs to be done is to have the brake fluid in your clutch lines flushed out from the reservoir to the slave cylinder, just like you would if you were flushing the brake system.

This is typically done with a pressure system, and is quite quick, and you won’t have anything to worry about once its done.

Also, you can’t ruin the transmission this way.
The clutch fluid is a completely separate system from the manual transmission fluid.
Nothing to worry about there.


Ouch!! Since you cycled the clutch a few times, sucking the mixture out of the reservoir will probably not get all the gear oil out. Do as Bladecutter recommended and flush the system.

I suspect you will be replacing the master cylinder and/or slave cylinder in the near future anyway. As a clutch wears the slave cylinder is pushed back raising the reservoir level. Since you were low in the reservoir, there is probably a leak. You might peel back the boot of the slave cylinder and see if there is fluid behind. Do the same at the master cylinder push rod. If you find fluid you know where the fluid went and which part will probably need replacement. You don’t mention the mileage on this Elantra but usually if either master or slave cylinder goes bad, the other is soon to follow. Usually both are replaced at the same time since it saves you an extra bleeding.

Hope this helps.