Bleeding Master Cylinder

94B2300 · Jul 15, 2014

Clutch - Bleeding Master Cylinder

I know there are many threads about this subject, but I've searched quite a bit and I have a unique problem that hasn't been covered anywhere else.

1994 Mazda B2300 - 2.3 with 5-speed manual.

I just replaced the clutch, flywheel, pilot bearing and the slave cylinder.
The clutch will not disengage and the pedal has little resistance, so there is obviously air in the system. I was unable to successfully bleed the air out, even while inverting the master cylinder at the firewall. I tried the next step by removing the snap ring at the master and pulling out the piston. As a result, it began leaking after I put it back together so I must have ruined the inner seal. :annoyed:

So I bought a new master cylinder and performed the bench bleed as shown in the video for Perfection Clutches. Here is the problem: that fitting on the end of the hydraulic line does not seal itself off - it will consistently drip during the bench bleed procedure. I did the bench bleed as best as I could, reinstalled and did a gravity bleed. I refilled the reservoir three times during the gravity bleed until no more bubbles came out of the slave. Now the pedal is even worse than before! I'm about to give up.
Is that leaky quick-connect fitting allowing air to get back into the system?

I've spent four days on this thing and I can't waste any more time on it. Any ideas?

Dale_K · Jul 15, 2014

I have a 2006 so the trucks might not be the same but mine has a bleeder on the slave not the master cylinder. The shop manual says to have somebody pump the clutch pedal 5 times and hold it down while a second person opens the bleeder (on the side of the transmission). Disregard if you know this doesn't apply to your model year.

94B2300 · Jul 25, 2014

Yes, I'm using the bleeder on the slave.

I've been at this thing for nearly two weeks and I still can't bleed it. I've gone through several bottles of brake fluid and I'm about to flip out. I don't have the money to have the damn thing towed and repaired somewhere. I've watched the video, I've read the Haynes, I've read the technical Ford service manuals, and I'm completely out of patience.

Does anybody have any advice on this??

4x4junkie · Jul 28, 2014

What worked for me one time since I was lazy and didn't feel like pulling the master out of the truck to bench-bleed it, I cracked open the bleeder on the slave just a little bit, then very rapidly slammed on the clutch pedal about 8-10 times in rapid succession, closed the bleeder, topped up the reservoir, and then repeated it an additional time.
At that point it produced a workable pedal which over the next 100 miles or so eventually returned to normal.

Worth a shot anyway. (this assuming that fitting doesn't leak when it's connected to the slave's fitting)

94B2300 · Jul 29, 2014

First off, thank you for the reply - I appreciate the help!

I have tried that technique a few times with no success. As a matter of fact, after the most recent bleeding process, I can push the clutch pedal to the floor with one finger. There is something seriously wrong here.

That fitting does indeed leak because it doesn't seal all the way when it's removed from the truck. It would steadily drip while I was bench bleeding it. I tried re-seating that little valve inside with a small punch but it continued to leak. While bench bleeding, I was able to quickly reinstall while keeping the reservoir full; so there should not have been any introduction of air into the system.

With that evidence in hand, it still doesn't make any sense to me that I can't bleed it. I'm currently bleeding it with the master inverted as well as the hydraulic line pulled away from the frame rail (so I can manipulate the bends to let the air purge). And yet, it just keeps getting worse.

Thanks again for the reply!

Dale_K · Jul 30, 2014

Here is a link to a video about bleeding a Ranger clutch master cylinder from another thread. Not sure if it applies to your year truck.

http://www.youtube.com/watch?v=Pd1KDCAhTLc

4x4junkie · Jul 31, 2014

I would suggest returning it then because of the leaking fitting.

94B2300 · Jul 31, 2014

The fitting that leaks is original to the truck; there is nothing to return. When I bought the master cylinder, it only came with the flexible line that leads to the reservoir. The replacement hydraulic line (with fitting) is $60 on Rock Auto, and I'm tired of buying parts and not solving the problem.

I just gave it another shot. I gravity bled it with over 60 fluid ounces of brake fluid and the bubbles never stopped coming out at the slave. The pedal practically falls to the floor, even after all that bleeding.

I am absolutely giving up on this thing before I start throwing my tools around. I'm going to gather some money together and have it towed somewhere. Whoever engineered this system was out of his frigging mind.

94B2300 · Aug 3, 2014

Well, I was able to step away from it and cool off enough to give it one more shot.

I removed the assembly (master, reservoir and lines) from the truck and bench bled it according to the Perfection video. I'm getting a full stroke on the master cylinder with minimal force, so I think I got a bad master cylinder out of the box. There is simply no compression, and there cannot be any more air in the lines. That coupler on the end isn't leaking anymore, either, so that can't be the issue.

I'm going to look for yet another master cylinder and see if that fixes the problem. Thanks to all who have replied.

scotts90ranger · Aug 3, 2014

Just as a note, the best way I've got air out of the master is fully compress the pedal and slip your foot off several times, I think that one might be too mad to have that work though but might be worth a shot.

adsm08 · Aug 3, 2014

I never ever try to bleed the clutch master in the vehicle. I take the whole thing, hard line and all out, hook it up at the slave, bleed it, then put it all back together.

Bleeding Master Cylinder

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