NO pressure after replacing master cylinder

[blue90]

So a friend and I replaced the clutch master cylinder in my 90 dx last night..... After installing the new hardware, we couldn't get any liquid or air flow through the clutch pipe... We've followed instructions precisely and can't quite figure out why we aren't getting some sort of pressure. We've removed the master about 3 times now rechecking all our attachments and connections seem to be solid. Only thing I can think of is that we don't have a pressure bleeder, and we don't have an air compressor to force the slave to kick back out

This should be a 45 minute job thats taken up about 7 hours of my time so far. And today is my Sunday, so any help is greatly appreciated. Thanks guys!

[deevergote]

I'm on about 3 years with this problem...

Did you replace the slave cylinder as well? If not, it would probably be wise to do that at the same time.

I don't know ANYBODY that uses a pressure bleeder. They just do it the old fashioned way... pumping the pedal and opening/closing the bleeder valve. I've gotten half-pressure in my clutch by doing it that way. I've replaced the master and slave twice, and I get the same result.

[blue90]

hmm

Should there be any reason I need to remove the slave while replacing the master?

[blue90]

also

While pressing in the clutch, there is A) No pressure and B) It doesn't engage the slave cylinder at all. ..... Should I manually engage the slave with my hand? When I do this, small amounts of fluid start coming out of the bleeder valve, and the reservoir levels fluctuate slightly........ So it seems like manually pumping the slave is bleeding the system better than using the slow press on the pedal...? Any insight?

[deevergote]

It's all connected, so yeah... if you get results by manually operating the slave, do it that way. Just don't suck air back into it.

Again, I do suggest replacing that slave. If it's original, it will probably fail fairly soon, and you'll have to do this all over again.

What made you replace the master in the first place? Was it leaking, or did you have no pedal pressure? If you had no pressure, the problem could have been the slave just as well as the master.

[19dabeast85]

With the clutch master, the pedal will not return until all the air is out of the line so you will have to return it by hand. Process:

1. Clutch pedal to floor.
2. Crack open bleeder at slave, let air out, close bleeder.
3. Manually pull the clutch pedal back up slowly.
4. Repeat steps 1-3 making sure to keep fluid level high.

You'll work the air out pretty quickly and when you get it all out the pressure plate on the slave will return the clutch pedal.

[CB7/KA8]

Did you bench bleed the master? Also, please replace the slave. Mine went out when I was stuck in traffic on 495. I had to push the car across 2 lanes of oncoming traffic and nobody bothered to stop and help.

[blue90]

Everythings been bled. Still no pedal pressure. Fml lol.

[blue90]

bleeding the master

Hey, apparently I didn't actually bleed the clutch master cylinder.... I was looking on youtube and I used the search filter on this site, but I couldn't find a how to on bleeding the master alone... Thanks for any help!

[deevergote]

Bench bleeding? As far as I know, the slave is the only one that gets bench bled. Most people don't bother. It just takes a little longer to get the air out.

[dj_ender]

Bench bleeding? As far as I know, the slave is the only one that gets bench bled. Most people don't bother. It just takes a little longer to get the air out.

I ALWAYS bench bleed my master cylinder, maybe that's why you only have half pressure deev. If you start out with air in the master cylinder, its near impossible to get full pressure, let alone the air bubbles out.

[19dabeast85]

Hey, apparently I didn't actually bleed the clutch master cylinder.... I was looking on youtube and I used the search filter on this site, but I couldn't find a how to on bleeding the master alone... Thanks for any help!

Bench bleeding is the same for all applications.....

1. Clamp the flange (NOT body) in a vise so it is as level as possible.
2. Find an adapter to screw into the brake fitting on the cylinder and put a piece of clear tubing from here into the MC reservoir
3. Use short 3/4" strokes to slowly pump all air out of the MC.
4. Cap off and install. Unscrew cap and install brake line.

But yeah the clutch MC doesn't necessarily need bench bleeding.

Another thing to try is take the bleeder completely off the slave and let gravity slowly pull fluid from the master, this worked fine with me. If this doesn't work attach a suction to the bleeder screw and suck the old fluid and air through. One of these HAS to work or there's major malfunction somewhere lol....it's possible your new MC is bad off the shelf.

[deevergote]

I ALWAYS bench bleed my master cylinder, maybe that's why your brakes only have half pressure deev. If you start out with air in the master cylinder, its near impossible to get full pressure, let alone the air bubbles out.

We're talking about clutch, not brakes.

[dj_ender]

We're talking about clutch, not brakes.

yeah, I know.

Edit....lol, just now noticed i wrote brakes up there...

[blue90]

Hey guys

Well, I guess there was a reason this was posted in the "beginner technical" thread lol.... I still am not sure exactly what we were doing wrong, but we got her running again. Started over again after removing the master and hand pumping it to ensure it was legit... I don't know, somehow or another we weren't getting everything sealed up right..... But we just kept bleeding it, and finally got some pressure back in the pedal.

I've probably driven about 50 miles on it, and it seems smooth as butter. One other question I had about the pedal itself is that at the top of it's motion there's about an inch of dead space where it just seems like no pressure.... After I engage past that inch everything is fine, can I remove that, or shorten the travel of the pedal? Thanks again, and sorry for the noob questions. I just acquired a factory service manual so I'll be doing some HW.