megaman311

Okay, so there have been threads on having a soft clutch pedal either after hard acceleration, or just revving your motor. I have been thinking about this problem, and I believe I have come up with a solution.

DOT 3 & DOT 4 fluids are glycol-based. This means that they absorb water. While DOT 5 does not. DO NOT USE DOT 5 IN YOUR COBALT!!! Our brake systems will not support silicone based fluid!

This means that the fluid is hygroscopic. Now, for those of us that have the vent on top of our brake reservoir this means that it can suck moisture from the air into the brake system causing issues with braking performance. This happens because the water in the system causes the boiling point to go down.

Now so why is this bad? Our clutch systems use the same reservoir.

With this in mind I decided to flush my brake system and reservoir. I used a vacuum pump to remove all of the old fluid. My soft pedal problems are no more! Now, I am not saying that this will fix a leaking slave cylinder or cure all of the problems that you may have with your clutch. But it should take care of most hydraulic issues that we will have with our cars. IE: Soft Clutch pedal under hard acceleration.

roadrage06

cool. nice find.

let's get a couple veterans in here to confirm some of this and possibly make it a sticky

Dainslaif

I was under the impression the TC used DOT4 from the factory.

megaman311

Does the TC reservoir have the vent on top like the SC? If it does, DOT 4 just means it has a higher boiling point than DOT 3. It will still absorb water like DOT 3. That does not change.

Dainslaif

I'm pretty sure my Ion doesn't have a vent on the reservoir at all, and the SC uses the same part...

R4race

I am quite certain that MOST brake MC caps have some type of vent on them. this is to let air in ABOVE the seal to compensate for the fluid displaced over brake pad wear. you should also notice that the seal expands when this occurs.

chris88z24

This has already been tried before, and it doesn't work.

megaman311

????

Silver Bullet

i had this same problem and it finally turned out that my clutch had a factory defect in it there was an oil spot on the pressure plate and one of the fingers on the clutch was misaligned cusing the clutch to hang up and give me a soft pedal feel, new clutch and pressure plate along with a new slave cylinder and im good to go.