ZPmadA

I replaced a line from the master cylinder to the slave (it had a hole) and bleed the clutch yesterday with a Motive Power Bleeder. I attached the Motive Power bleeder to the resevoir, and pumped it to 10psi making sure fluid was in the line. Then I opened the bleed valve on the slave and let it drain out until I didn't see anymore air bubbles. (I saw very tiny air bubbles though, maybe my fluid is old?). It felt ok when I fnished and I parked it. A few days later I pulled it out the garage and it was feeling a little spongy.

Should I have bleed it somehow with the motive power bleeder attached to the slave to push the air from the bottom up?

Or is it likely my fluid needs to be replaced? (I attempted this 6 months ago and had half a bottle left so I used that) I didn't think it would be this spongy since the bottle was closed, but half empty.

EDIT: reservoir was still full when it felt "spongy", and no fluid was on the ground

Dimi 944

Your fluid could have picked up moisture. This happened to me whe I used older fluid.
Also, make sure you clean and dry the power bleeder before each use. It is amazing how much moisture it picks eventhough it is closed.

Yarf

I would replace the reservoir fluid with fresh fluid and then bleed the system.

ZPmadA

How do I get the fluid out of the reservoir? Just keep pushing fresh fluid in from the top and pushing the old stuff out the bottom? I have an entire can just for the clutch and don't have time to do the brakes

Dimi 944

You can use a turkey baster to suck most of the fluid out. Fill it in with fresh fluid and then bleed the system.

ZPmadA

It seems OK after fresh fluid thanks everyone.

Dimi 944

You are welcome.

67King

Did you depress teh pedal once you opened up the bleed valve? You are supposed to do that, bleed it, close it, then once you do that, manually pull up the pedal frorm the floor, which will draw fresh fuild from the resivoir.

HICKS

Where did you guys get your motive power bleeder from? It seems pelican has them the cheapest, anywhere else?

kingston944

Got mine on Ebay around $75.00 I think.

AScholtes

I got mine from Zims for like $60 or something

teamking

Maybe this is a dumb question, but why would water in his hydraulic fluid cause a spongy clutch pedal?

AScholtes

because water doesnt compress and therefore effects the amount of pressure generated from the same volume of brake fluid that has no water content. Brake fluid being hydroscopic, naturally takes in water and should be changed using a new, unopened bottle at least once a year for best performance (or more frequently for track cars)

teamking

Thanks for the response. But, it makes no sense to me.

Brake fluid is an ideally non-compressible liquid. You are saying that by replacing one non-compressible liquid (brake fluid) with another (water), that the volume of fluid changes. I don't get that.

And then you say to change your brake fluid once a year. So how is brake fluid that's been sitting in the reservoir for 10 months OK while brake fluid that was sitting in a power bleeder for six months is full of water?

I'm not saying that water is a good fluid for the system-- surely it would lead to corrosion and seal failure over time. But I don't understand how it explains the symptoms seen by the OP.

I don't mean to offend anyone... just trying to understand.

aj986s

FWIW, I think that in a cold state, water and brake fluid will probably work similarly. The problem with water is heat. Once the brake calipers get hot, the water will boil into vapor, and the vapor can be compressed, causing the softer pedal. My guess is that the problem is more likely air bubbles trapped in the system, along tubing surfaces, etc. that need to be evacuated in order to get the system completely filled with fluid. Several cycles of bleeding will usually move/consolidate these bubbles until they're finally expelled. I don't know if from a scientific/hydraulic's perspective whether liquid water and brake fluid might compress differently. And, as mentioned, water also leads to corrosion issues.

But, condensation in the Motive bottle is an issue, and getting water into the brake system is a much greater concern than for the clutch. Personally, I've resorted to only using the Motive "dry", where I monitor fluid level in the brake/clutch fluid reservoirs, and using the Motive only to generate pressure. Do need to be careful to not empty the fluid reservoir. But fewer cleanup & storage issues of the Motive.