OT: is prefilling an hydraulic clutch system practical?

tnmgcarbide · May 28, 2020

i'm in the midst of replacing the master and slave
cylinders in my wife's Honda element . the master
isn't too bad after removing the battery, airbox
and intake . the slave is a real bitch to get to,
and there's nothing to move to get to the bleeder
valve.

would there be any reason not to pre-bleed the whole
system outside the car, then install as a unit? i
know it's common to fill + prebleed a brake master

john.k · May 28, 2020

Not one of those slave cylinders thats around the gearbox shaft ,is it.They are quite popular with carmakers who want to guarantee dealers that owner repairs are impossible.

Ecarter · May 28, 2020

No reason not to try. As long as you can put it all in as a unit without removing lines it should work. Restrain the piston in the slave so it dosent push out while you're bleeding it. I know nothing about how the hyd clutch system fits into this car, but I've done it before on other cars without problem.

I've also carefully "reverse bled" some using the bleeder on a nearby brake caliper and a good clean length of hose to connect to the slave bleeder and carefully push fluid back through the clutch system. This works in a pinch for systems that are hard to get started taking fluid when empty.

Garwood · May 28, 2020

Typically you buy as a complete sealed set and install. Done.

Bleeding outside the car works fine too.

tnmgcarbide · May 28, 2020

replacing master and slave, seemed logical to assemble as a sysrem and fill beforehand, but i'm a machinist, not an auto mechanic.
i really despise working on most cars, especially when the engine is shoehorned under the hood

David Utidjian · May 28, 2020

I used to do a lot of this kind of work but it has been decades(!) I stopped working on cars before the Honda Element even existed... so I went to look to see if someone has posted how they did it. Found a pretty good video on youtube. In the video she removed it all as a unit. From the way those parts fit together (reservoir, master, lines, slave) it seems like a good idea to do it as a unit. She is careful to clean out the old fluid and flush it with brake cleaner then air from all the lines and reservoir. She does not bleed it outside before installation. Afer installation she does a "gravity bleed" first then uses a vacuum bleeder at the end. As far as basic procedure goes the video shows exactly how I would have done the job. Only thing left out that I would have done is to apply they vaccum to the bleeder at the same time as I am tightening the bleeder. Doing it that way insures that any little bubbles left in the slave cylinder are drawn out by the vaccum as it is sealed off.
Link to video: YouTube
Link to vaccum bleeder: How to use Vacuum Brake Bleeder - Capri Tools

-DU-

tnmgcarbide · May 28, 2020

i saw that video too. funny how the leave out how you
have to remove everything under the right side of
the hood -battery, fuse panel ,wiring harness, intake , airbox, battery
tower , vacuum lines ,etc just to access the clutch hydraulics... actually painless compared to the rest of the job , which took me over three hours - ALL
the fasteners were impossibly frozen , and i broke
an S-K 3/8 universal and damaged another (crapsman)
removing bolts i could barely see down two 10" extensions plus another 4"on the end. no way in hell
i could fit my meathooks way down in there to get
any leverage (24" cheater pipe) , much less operate a bleeder valve . pre-bleeding the line was a godsend, but the repair still sucked.

kustomizingkid · May 29, 2020

I always power bleed these, about 50% of the time they need additional manual bleeding. Honestly these are easy as hell to bleed. Just be glad you didn't have to do a starter.

tnmgcarbide · May 29, 2020

i agree. vacuum it . i have an old Gomco medical vacuum pump -with the glass belljar and stopper- that
i use for brakes, but it would be nearly impossibe for me to maneuver a wrench on the fitting if i could actually get a hose on the thing.

BT Fabrication · May 29, 2020

tnmgcarbide said:
i agree. vacuum it . i have an old Gomco medical vacuum pump -with the glass belljar and stopper- that
i use for brakes, but it would be nearly impossibe for me to maneuver a wrench on the fitting if i could actually get a hose on the thing.

Yes you can, as long as its a sealed assembly when you install it.
other then that, there is always a way to get at those bleeder valves, it's why there are flex head wrenches etc.
no need for a hose on it. just need a guy in the car to push it down, then you open, let the air out then close and he lifts the pedal and repeat till there isnt any air.

David Utidjian · May 29, 2020

I wonder what the 'official book time' is on remove and replace the master and slave cylinder is. All that rust and corrosion leading to seized up parts is one of the reasons I got out of being an auto mechanic. Older more worn out poorly maintained vehicles are more expensive to fix in time and headaches than better maintained ones. Something that many customers can't seem to understand.

-DU-

moonlight machine · May 29, 2020

tnmgcarbide said:
i saw that video too. funny how the leave out how you
have to remove everything under the right side of
the hood -battery, fuse panel ,wiring harness, intake , airbox, battery
tower , vacuum lines ,etc just to access the clutch hydraulics... actually painless compared to the rest of the job , which took me over three hours - ALL
the fasteners were impossibly frozen , and i broke
an S-K 3/8 universal and damaged another (crapsman)
removing bolts i could barely see down two 10" extensions plus another 4"on the end. no way in hell
i could fit my meathooks way down in there to get
any leverage (24" cheater pipe) , much less operate a bleeder valve . pre-bleeding the line was a godsend, but the repair still sucked.

You are so lucky you did not twist any off!

J Grainger · May 29, 2020

Reminds me of changing the aux belt on my old Passat.. the grill is the first thing to come off those and the captive nuts were spinning.

Bill D · May 29, 2020

I remember years ago there was a special Volvo bleeder wrench. It looked like a deep socket with a handle brazed on. I think you used a standard wrench to loosen the bleed screw first. Then this deep socket had a o-ring inside and a hose out the top for the fluid to go out.
Bil lD

David Utidjian · May 29, 2020

Bill D
I had one of those. I don't remember what size it was or vehicle it fitted but I do remember it was finished in black oxide with a red plastic covered handle. IIRC it was an odd size and if I had the tooing I would have made them for all the sizes of bleeders I worked on.

Other little trick I did was remove the bleeder and smear a bit of Girling red brake assembly grease on the threads. Helped in preventing air from getting sucked in via the threads.

-DU-

Strostkovy · May 30, 2020

I replaced the master cylinder in my truck and bled just the master cylinder first, loosely threaded the connections together, then pushed the slave cylinder back to get some fluid to squirt out the fitting then tightened up the fitting. I have no air in the lines that I can tell and it is all working great.

Not exactly what you plan to do, but maybe that info means something.

SBAER · May 30, 2020

I have successfully bled a hydraulic clutch system with no bleed screw (2001 f250) by pulling a vaccuum on the the lid of the master cylinder with a vaccuum pump. It took a while.

Chip Chester · May 31, 2020

One-man vacuum bleeders are good. So is 'bench bleeding' if you can keep it assembled and upright as it's installed.

On my 60's sports car, I ran a flex line from the slave bleed valve back up to the reservoir. Then I put a self-bleed fitting on the hose, and position it over the reservoir when bleeding. Make sure things are full, open up the self-bleeder (topside) and start pumping the air out. No need to re-fill. After your leg gets tired, tighten self-bleeder, wipe stuff off, and test clutch. So far, so good...

OT: is prefilling an hydraulic clutch system practical?

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