[968bill]

After replacing the clutch I found my clutch master cylinder was leaking so I ordered the master cyl and the pressure line, the supply hose had been replaced by PO earlier.



After installing the parts I tried to bled the system, it took me many tries to get it right, here's what I learned.



First let me say when I've used the Motive bleeder in the past I did NOT put fluid into the Motive tank, I just made sure not to run the brake reservoir empty when bleeding brakes. This has always worked fine for me in the past even when bleeding a clutch system that only needed flushing. I don't like fluid in the tank since it will absorb water and can get contaminated in the tank easier than in the brake fluid can.

Unfortunately I learned the clutch portion of the reservoir inside the brake reservoir is very small, when using a pressure bleeding system (Motive) it is very easy to empty the clutch portion and get air right back into the clutch lines. Unfortunately, leaving the bleed screw open long enough to get air out the bottom the clutch portion of the reservoir winds up draining the clutch area and sucks more air in from the top! I'm embarrased to think how many times I did this.



So, I used some fresh clean fluid, rinsed out the Motive and put about 1/2 qt. in the Motive tank. Proceeded to pressurize the system, 8 lbs will NOT work, it won't get the air bubbles small enough to flow through the entire system, I wound up going to 18 - 20 lbs. After bleeding with a steady supply of fluid on the reservoir end and using a sufficient pressure from the Motive the system bled very quickly, I still had a good bit of fluid from my 1/2 qt in the Motive.



The pedal did feel a little strange but after driving it a few days it's feeling much better, as others have suggested I'll give it a few more days and bleed it again.

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[Aahz]

I watched my clutch system bleed out onto the 405 freeway last week - seemed pretty effortless. <img src="/forum/images/smilies/968/huh.gif" class="smilie" alt="" />

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[Bob Kovacs]

Thanks for the tip! I'm having a similar problem right now and this is very timely.



Also, since the hose that takes fluid from the brake reservoir to the clutch cylinder is located toward the front of the brake reservoir, tipping the car up in back will help keep fluid flowing into the hose. Standing the car on its nose would be ideal! <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" /> Seriously, a little slope toward the front will definitely help keep air out of the system.



I have a Motive Power Bleeder on order and hope to get it before the weekend, so that I can finish the work on my car.



--Bob

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[apex]

I can confirm that it is VERY easy to blow past the fill tube in the reservoir and introduce air into the hydraulics!



Also: my experience was such that it was very hard for me to get all the air out of the system - even with a Motiv pumped up to 20 psi and after a liter of fluid! But keeping the nose down helps... and driving the car for a day removed the remaining squishyness from the pedal.

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[Dave]

Yup, did this once in the old 944. Let the fluid level dip too low, suck air in, all bad.



A solution (given to me by good P-car mechanic) was to:



1) Fill reservoir to top

2) Open clutch bleed screw

3) Allow to "gravity bleed" for 30 minutes

4) Close it up and Motive one more time



The gravity bleed is slooooooooooow. Kinda like watching grass grow. That said, it seems to allow air to naturally migrate out. Not sure how, just know it worked when ALL else failed.

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[apex]

Roger the gravity bleed. It really seems to help!

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[968bill]

When I first did the clutch mechanical portion the car was on an upward tilt, I left it that way when I did the first (of many) bleed attempts. That's when I discovered just how small the clutch portion of the reservoir is! After that I put the car on blocks of wood (JWW's system) with the front a little lower than the rear, it helped a great deal but not enough to get all the air out before the reservoir emptied. I also tried the "open the bleed screw and let it drain" method but I guess I wasn't holding my mouth quite right or something....



For me, if I'm just going to be doing the "flush out old fluid replace with new" maint. I'll stick w/ empty Motive tank process, but if I need to get air out of the clutch line I'll use the "put fluid in the Motive tank" process. For brake system flushing there's plenty of fluid in the reservoir that I don't need fluid in the Motive.



JMO

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[sayporsha]

The clutch portion of the reservoir is indeed VERY small. Also, the line is short so it's VERY easy to over-bleed it and introduce air to the system. Therefore fill, bleed 2 pumps, fill again, bleed 2 more pumps, fill again, bleed 2 more pumps and you're done. The gravity bleed just doesn't work. Oh, and it helps to immobilize the clutch fork with a block of wood. Just make sure the pedal man doesn't push too hard and blow a seal or hose.

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[tloof]

I'll give you guys a little tip on how to easily bleed ANY brake system and clutch hydraulic system. The following method is how we bleed the systems in airplanes which are extremely difficult due to the length and height between the reservoir and the slave cylinder. The method is to bleed in reverse from the caliper/slave cyl up to the reservoir so that all the air in the system is moved upward (which is what it wants to do naturally in any fluid). Buy a relatively cheap hand pump brake bleeder (about $50 or so) with fluid bottle. Drain the entire system first by opening the bleeder screw on the caliper/slave cyl, and then use the hand pump to suck all remaining hydraulic fluid out of the system thru the bleeder screw (do this for each wheel cyl as well). Now reverse hand pump and slowly pump fresh fluid into the bleeder screw (with it open of course) until the fluid flows up into the master cyl reservoir until it is at the half level (you don't want to let it overflow such that fluid gets on your paint, or it will ruin the paint). Close the bleeder screw and then fill the master cyl up to its max level at the reservoir itself. By flowing upward all air should have been completely evacuated in the process and you are now good to go. Test to be sure that there is no spongy action in use, if so then rebleed in the conventional way using the Master cyl as the pump and bleeding at the caliper/slave cyl (this is rarely required since the air is almost always evacuated completely when pumping upward).



This method works really well on clutch hydraulic systems!

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[apex]

now that's thinkin' outside the box...

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[Bob Kovacs]

I got a Motive Power Bleeder, put fluid in the container and it worked like a champ. The clutch hydraulics bled quickly and I got it right the first time. I strongly recommend using the Motive Power Bleeder and adding fluid to it as described in the unit's instructions.



It's also MUCH easier to bleed the clutch slave cylinder with the starter out of the way. Pulling the starter is easy and I just let mine dangle by the cables, which are easily heavy enough to support the weight.



The Motive Power Bleeder is just $50 or so and seems like a more expensive tool. If you do your own brake work, it's a bargain.



--Bob

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[Tom in Austin]

Haven't tried this myself, but following tloof's theory, have read advice that you can bleed the slave by just pushing the plunger all the way into the cylinder, thereby forcing fluid and any air up through the master and into the resevoir.



Has anyone tried this technique?

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