83 porsche 944 NA bleeding the clutch

[thomas944]

Replaced master and slave cylinders today. First we tried to bleed by pumping the pedal a couple times and opening the valve but it didnt seem to work. Now we are trying to bleed the system with oil can attached to hose attached to the bleeder valve. My dad pumps the can and I look for bubbles in the reservoir. I see a few but not very often. I try and depress the pedal with the valve closed but it goes straight to the floor and stays. I have to pul it up. We have to slave cylinder attached and seated properly but do we need to take it off so the piston is completely open while bleeding it? Are we doing something completely wrong and just overlooking something? Please help!

[Rasta Monsta]

[89-944NA]

+1 Rasta

[Cocacolakidd]

Back in the day before the Power Bleeders, and with a one man garage how did we bleed brakes ?

Get a 4'-0" piece of plastic hose (See through plastic/vinyl, etc.), jack up rear of 944, and fill the Master Cylinder Reservoir until the complete front half is full of fluid. Place the 4'-0" piece of plastic tubing on the Clutch Slave Cylinder Bleeder Valve. Then loop it up at least 12" and Fasten in place (Usually Duct tape), and then down into a bucket or pan. Loosen the bleeder valve on clutch slave until you can see some fluid leak out into the tube. Go inside the cab and pump the clutch 8 times, each time pulling up on the clutch pedal to rest, and final time leave the clutch pedal in up position. Under the car inspect the upper loop of the bleeder tubing for air bubbles. If no air bubbles in upper loop close off the bleeder valve - finished.

If there are bubbles in upper loop repeat until free of air bubbles.

Just another way to save money and bleed your own brakes/clutch system.

[flash968]

definitely the motive

never ever EVER pump the pedal. it will create microbubbles which later become bigger air pockets.

to bleed hydraulics manually it is a stroke by stroke process, generally requiring 2 people(one guy at the bleed screw - one guy at the pedal)

open bleed screw
push pedal gradually and evenly to the floor and hold it there
close bleed screw
release pedal
repeat until no bubbles come out

[Cocacolakidd]

never ever EVER pump the pedal. it will create microbubbles which later become bigger air pockets.

to bleed hydraulics manually it is a stroke by stroke process, generally requiring 2 people(one guy at the bleed screw - one guy at the pedal)

open bleed screw
push pedal gradually and evenly to the floor and hold it there
close bleed screw
release pedal
repeat until no bubbles come out

Bah-Humbug

In one sentence you state never to pump the pedal, then three sentences later with two people you state it's OK to pump the pedal - make up your mind.

I've been doing it the old fashioned way for 40 years, and with 100's of thousands of miles and never had a problem.

With the old fashioned one man way you are actually setting up a siphon that is constantly bleeding the system even when the pedal is at rest.

[flash968]

i never said "pump" the pedal, which by definition is a fast motion designed to build pressure. that is EXACTLY what not to do.

i just love the old "never had a problem" line, as if that had any validity. that just means that you've either been lucky, or don't know the difference. nobody has every had a problem with anything, until they do. does that mean that it was fine all along? obviously not.

i have also been doing this for at least 30 years. i guess you've just been doing it wrong for 40. no worries. i learn new stuff every day too.

you can read just about any manual on hydraulics and learn about microbubbles and how they are formed. you NEVER allow the pedal to travel back with the bleed screw open. also, fast movement creates turbulence in the line, causing microbubbles. you should be moving the pedal smoothly and evenly, not too fast, and only letting it back up after you close off the bleed screw.

[mikepellegrini]

+1 Rasta. Motive Bleeders are the best!

[CHICKS]

+15 on the Motive. The Motive is the easiest and fastest way to do.

[porschetub]

Originally Posted by Cocacolakidd

Back in the day before the Power Bleeders, and with a one man garage how did we bleed brakes ?

Get a 4'-0" piece of plastic hose (See through plastic/vinyl, etc.), jack up rear of 944, and fill the Master Cylinder Reservoir until the complete front half is full of fluid. Place the 4'-0" piece of plastic tubing on the Clutch Slave Cylinder Bleeder Valve. Then loop it up at least 12" and Fasten in place (Usually Duct tape), and then down into a bucket or pan. Loosen the bleeder valve on clutch slave until you can see some fluid leak out into the tube. Go inside the cab and pump the clutch 8 times, each time pulling up on the clutch pedal to rest, and final time leave the clutch pedal in up position. Under the car inspect the upper loop of the bleeder tubing for air bubbles. If no air bubbles in upper loop close off the bleeder valve - finished.

If there are bubbles in upper loop repeat until free of air bubbles.

Just another way to save money and bleed your own brakes/clutch system.

Great answer it's just not hard to do,leave the power bleeders for brakes thats what there best use is.
BTW you should replace the cups in your slave cylinder cheap and easy to do.

[Cocacolakidd]

i never said "pump" the pedal, which by definition is a fast motion designed to build pressure. that is EXACTLY what not to do.

i just love the old "never had a problem" line, as if that had any validity. that just means that you've either been lucky, or don't know the difference. nobody has every had a problem with anything, until they do. does that mean that it was fine all along? obviously not.

i have also been doing this for at least 30 years. i guess you've just been doing it wrong for 40. no worries. i learn new stuff every day too.

you can read just about any manual on hydraulics and learn about microbubbles and how they are formed. you NEVER allow the pedal to travel back with the bleed screw open. also, fast movement creates turbulence in the line, causing microbubbles. you should be moving the pedal smoothly and evenly, not too fast, and only letting it back up after you close off the bleed screw.

Idiot -

I have read several manuals on Fluid Mechanics, and studied in several classes of Fluid Mechanics, along with six years of study and college credits towards my masters in Mechanical Engineering.

I do see you did not say "Pump", you said "Stroke" and "Push". You also stated by definition that "Pump" was a fast motion (Who said that - you!) - Here you are just showing your ignorance. By the way learn to use a spell checker, plus your grammar and diction tells me you barely graduated out of a dysfunctional California School System.

So do you really have any idea where the air bubbles come from in a sealed hydraulic system? - surely not from out side - so then where? Can you balance a chemical equation ? that's what it takes to prove where the air comes from.

By your definition of the mechanical system any old Hot-Rodder should wind up with a non functioning hydraulic system because they speed shift to many times. So when they pump the clutch to fast this always creates the air bubbles? - haw haw.

Other people complain about water accumulating in an older hydraulic system - So if this is true where does this water come from in a sealed system? Maybe the same place the micro bubbles come from? Remember we are still working with a type of carbon chemical equation.

[Tervuren]

Cocao, a little reading comprehension and you'd understand better, he's talking about pumping the pedal rapidly with the bleeder valve OPEN. ok?

[flash968]

tervuren - correct

sodahead - actually i graduated 9th in my class (man, was that a long time ago), attending college classes at the same time, and then went on to finish college on scholarship, and was a mechanical design engineer for DOD for years.

while i choose not to capitalize when i type here, my grammar is nearly flawless, and my diction is intentional.

continue to bleed things however you want. i'll choose to do it right. a quick google popped these on top. not one of the results says to pump the pedal and ALL of them say to make sure the bleed screw is closed before releasing the pedal.

How to Bleed a Hydraulic Clutch - Team Rip Engineering
How to Bleed a Clutch Master Cylinder | eHow.com
Bleeding or Flushing Brake and Clutch Hydraulics

[Cocacolakidd]

Cocao, a little reading comprehension and you'd understand better, he's talking about pumping the pedal rapidly with the bleeder valve OPEN. ok?

Speaking of reading comprehension, he is the only one who is insisting that the process is rapid, well maybe you also.

continue to bleed things however you want. i'll choose to do it right. a quick google popped these on top. not one of the results says to pump the pedal and ALL of them say to make sure the bleed screw is closed before releasing the pedal.

Try it sometime, you may like it. With a siphon involved there is only hydraulic fluid near the bleed valve to be pulled back into the system. Properly done with the upper loop of the tubing filled with fluid bleeding the clutch is a one person job.

The whole point was to introduce a method where a single person, without access to a power bleeder, can make a simple repair.

[flash968]

i've done it that way, before i learned why it was the wrong way. i had the "pleasure" of learning all about hydraulic systems in cars from 25 years of dealing with british cars, notorious for their bad hydraulics.

"pump" from the dictionary:

• apply and release (a brake pedal or lever) several times in quick succession