Clutch bleeding failure using motive power bleeder, why

Yuta · 10-23-2015, 03:22 PM

Hi guys,

Car has been sitting three years with clutch pedal pushed in and clutch slave cylinder removed. The reservior always have fluid and brake is alway hard.

Now I finally got the engine running and was trying to bleeder clutch.

I have a new slave cylinder installed because old one looks rusty on rod, dont want to take chance. I also ordered Motive Power Bleeder.

Thought it is going to be a easy job accroding to video instrucions on youtube..... But I just couldn't get the pedal hard. Pedal can't feel anything..

Basically what I did was.. I pressurizie bleeder without fluid to 15 PSI. I noticed there was a slow drop in pressure///But I didn't see any fluid leakage in the system..

Then I add fluid in the bleeder and pressurize it to 15 PSI again. Waited a while, then open the bleed screw on the back of the slave cylinder. Fluid came out without bubble... I let it drain for a little whilte and then tightened it. Pedal still not hard. Don't feel anything on pedal...

What is wrong? Will the master cylinder be bad? It was replaced one year ago before I parked the car....something is wrong with how i did it...

mytrplseven · mytrplseven's Garage

Why did you force air into the bleeder? I would think doing that would introduce air into the system. It looks like you're going to need to force more fluid into the clutch slave and periodically move the clutch lever in and out and bleed to exercise the bubble out. To be clear, I've never had to do a clutch bleed before, but this procedure sounds to me, to be a logical method.
Good luck.

jhowell371 · jhowell371's Garage

Remove slave from car and let hang. Make a push rod retainer for the slave with two bolts and steel strap or use a big c-clamp and a socket. Twist slave carefully to allow bleeder to point straight up being careful to not kink the hard line.. Now bleed as normal with the clutch pedal, reinstall and go enjoy

Bradical · 10-24-2015, 05:05 AM

First of all, you shouldnt exceed 5 psi, 15psi is too excessive. I would be willing to bet your issue is a ruptured blue hose- the one in the picture looks pretty dry-rotted. You also have to keep filling the reservoir as the master and slave will fill with fluid, the level in the reservoir will fall low in the outer channel for the clutch and you will push air into the system and then the process has to be started all over.

JonA · 10-24-2015, 05:42 AM

Yes, 15 psi is too much. Make sure the brake/clutch resevior stays full of fluid, in the picture it looks like you are pushing some air thru the Motive line.
The clutch pedal must be in the up position and I always pump the clutch pedal when the bleeder is open while power bleeding to make sure no air is in the clutch master but that may be more superstition than physics on my part.
Try again before you go tearing everything apart. The Motive bleeder usually gets the job done.

Good luck,
Jon

flash968 · 10-24-2015, 05:53 AM

15psi while just a touch high, is within spec for the motive. i use 11.

never ever pump the pedal

check the condition of the blue line. believe it or not, if that has a crack in it, it can result in inability to bleed the system.

to answer your other question, yes, you could have a bad master. there should be signs of fluid on the seal inside the car though. you could also have a blown or bad line between the master and slave. this is extremely common.

even if you get it all working, there is a more than 50% chance of failure of the next weakest component in the chain. this is why all components of an hydraulic system should be changed all at the same time.

Bradical · 10-24-2015, 07:58 AM

Quote:

Originally Posted by flash968

even if you get it all working, there is a more than 50% chance of failure of the next weakest component in the chain. this is why all components of an hydraulic system should be changed all at the same time.

This! Almost every "I cant get my clutch to bleed!" post ultimately ends with the OP replacing everything.

...also, I think I read somewhere that pumping the clutch pedal during this process was an "unforgiveable offense"? Ha!

flash968 · 10-24-2015, 03:03 PM

hydraulic systems are a mixed blessing. they work great when they work. unfortunately, if they are neglected, they go bad, and they go bad all across the system. it's the nature of a fluid that moves from one component to another. if one is contaminated, so are the others. it's not an "if" but "when" for the next weakest link in the chain to fail. after watching this for 11 years now, and having had a shop and working on these things for 30 years, there is a strong database supporting the over 50% failure rate of changing only one component. sad but true reality. i sell a lot of clutch hoses that way though.

as for pumping, what many do not understand is that this introduces microbubbles, which is exactly what you don't want. you cannot "build pressure" on the hydraulics. if that were true, the system would be worthless. the only thing that builds pressure is air. that's why pumping the pedal does not work. it might feel "fine" when you think you are finished, but then a day or so later, the pedal will feel mushy again.

if you have to bleed things manually, then it's "push (slower than you would depress the pedal to shift gears poking around town), open valve on the way down, close valve when the pedal hits bottom, release pedal, repeat". never ever ever pump the pedal.

mytrplseven · mytrplseven's Garage

Quote:

Originally Posted by flash968

hydraulic systems are a mixed blessing. they work great when they work. unfortunately, if they are neglected, they go bad, and they go bad all across the system. it's the nature of a fluid that moves from one component to another. if one is contaminated, so are the others. it's not an "if" but "when" for the next weakest link in the chain to fail. after watching this for 11 years now, and having had a shop and working on these things for 30 years, there is a strong database supporting the over 50% failure rate of changing only one component. sad but true reality. i sell a lot of clutch hoses that way though.

as for pumping, what many do not understand is that this introduces microbubbles, which is exactly what you don't want. you cannot "build pressure" on the hydraulics. if that were true, the system would be worthless. the only thing that builds pressure is air. that's why pumping the pedal does not work. it might feel "fine" when you think you are finished, but then a day or so later, the pedal will feel mushy again.

if you have to bleed things manually, then it's "push (slower than you would depress the pedal to shift gears poking around town), open valve on the way down, close valve when the pedal hits bottom, release pedal, repeat". never ever ever pump the pedal.

Well, like I said, "I've never had to do one myself". Thanks for clarifying that info. It'll surely help me down the line if mine fails.

pfarah · pfarah's Garage

I had an issue with no flow while first using the Motive. It turned out to be large particles in the brake line which prompted me to reduce overall system pressure to about 3-5psi, then remove each bleeder valve (one at a time) until flow began. Three out four bleeders were clogged!

This is why it's very important to regularly flush the entire system as required.

JonA · 10-26-2015, 03:55 AM

OK, poorly written post on my part. What I do is pump the pedal once as the Motive bleeder is pushing fluid thru the system. This would be to clear any air that might be trapped in the clutch master cylinder. With the whole system under 5-10 psi of positive pressure I can see no way this would introduce air into the system. Always done it this way and maybe it doesn't help but it hasn't caused problems.

Jon

flash968 · 10-26-2015, 05:03 AM

if you have a leak elsewhere, then when you release the pedal, it will draw in air. in anticipation of the next question, while you might, you won't necessarily see fluid escaping at the leak, because air molecules are much smaller than those of the fluid.

thomasryan · 06:15 AM

I somewhat lost my religion during the bleeding process.

Replaced the master and slave and it failed to bleed due to a ruptured flex line. A lame initial diagnosis but I did have fluid running down the carpet and the blue supply line was decomposed.

After replacing the flex line, raising the rear of the car a few feet and filling from the bottom gave me enough pedal to use the motive and manually bleed for the final step. I had to manually massage the slave cylinder through the inspection port to work out the micro bubbles on the bottom and I used a 19mm socket to block the clutch fork when it came time to manually bleed at the end.