BJ74 Clutch Master rebuild/clutch booster seal replacement w/pics (1 Viewer)

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May 22, 2014
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Hey all. So I found myself in the unknown after chasing my clutch fluid disappearance to my clutch master after replacing the slave (may or may not have been needed), and right after that discovery, my truck stopped shutting off. It was then I discovered it has a clutch booster, something I never realized. I had an HZJ73 a few years ago, but never had to touch any of this so I never thought much of it.

So the fix was pretty simple, but since I had never played with this system before I found myself with little info and no pictures on what I would find in there, so I snapped a couple quick pics along the way of the important bits. I'll throw them up here so now someone in my shoes knows what they're going to be looking at.

So first, the symptoms. I suddenly began losing clutch fluid at an alarming rate and couldn't figure out where it was going. I changed the slave because it was pretty haggard and may have been weeping, but that didn't stop it. Soon after, my truck stopped shutting down with the key. I scrambled to locate the VSV in the parking lot at work before a meeting, I did a little internet search and realized it had a clutch booster, and the vacuum is where the clutch fluid is going (the engine was eating it). That night I spent a few minutes figuring out how the shutoff works, and realized that if I pulled the vacuum line from the booster (under the clutch master on a RHD) and plugged it with my thumb with the key off, it would pop the VSV and shutdown like normal, which means the clutch booster wasn't getting sealed. This was a bummer revelation because the booster isn't made anymore, neither is the clutch master cylinder. I reached out to Cruiser Outfitters and Kurt explained that there is a seal behind the master that gets worth out, and that a clutch master rebuild along with the firewall booster seal usually does the trick, so I ordered parts. I was super worried about having a bad booster because I did see some seepage out of the pedal side, and I hit it with WD40 to see if that would create a seal that would shut down the truck... it did seem to work one time, more on that later. I had to drive the truck to work for the rest of the week (I bought it to daily drive and then had an opportunity to offload my Volt, so I did it before getting a chance to shake the BJ74 down). Randomly the shutoff would work but I usually had to pop the hood and hit the VSV. Not a good look picking my daughter of from chichi private school.... It drank a half reservoir of clutch fluid per day (about 15 miles total commute in LA traffic), and I had to bleed it every couple of days. The clutch would also randomly become stiff, a sign the booster wasn't working.

The removal of the clutch master is super simple and not really worth getting into too deep. Remove the heat shield with a 12mm, a 10mm wrench removes the line, a 12mm ratchet with an extension takes care of the two of the three nuts holding the master on, a box end gets the bolt that's behind the brake booster, don't lose the nut, there's just enough space to get the nut off and to slide the clutch master off. It is not attached to the pedal like a normal clutch master, it just comes off. The pedal linkage attaches to the booster, which pushes this little nub into the plunger which simply receives it. This is what you'll see, notice the pile of gunk around the edges of the seal...
IMG_0640.jpg


There's a little spring retainer thingy with tabs that keeps a seal anchored back there. During the day the shutoff was working properly after not driving the truck all weekend. At the time the seal was holding a vacuum and even hours after driving there was still pressure in the booster, which hissed when I poked and pried on it with a screw driver. Here's a picture of the retainer and how it sits against the seal, the master is presses onto the retainer.
IMG_0643.jpg


To remove the retainer, use a flat head to carefully pry the tabs back a little. There is no groove, just the friction of the tabs against the little housing, then work the retainer out without destroying it, then work the seal out using a screwdriver around the edges.

My booster was leaking because all of the crap that had been blown in there from the leaking master was interfering with the seal. This was actually a pleasant surprise. There was years worth of junk piled up in there. It was indeed contaminating the booster, which is where the seepage was coming through on the other side. This has since stopped, so I know the WD40 seeming to create a seal was happenstance. Sorry the picture kinda sucks but you get the idea...
IMG_0642.jpg

I am a little worried the booster diaphram was compromised by being hosed down by brake fluid, but it seems to have dried out and works just fine. I cleaned housing out really well with a rag. The replacement just gets worked back in. I flattened the retainer with a rubber mallet against the garage floor very gently before reinserting it. You just pop it in there against the seal.

The master rebuild is really simple. You remove the c clip and in mine...... nothing happened.
IMG_0645.jpg

The plunger wouldn't come out. I looked at the replacement plunger and there was no reason it was being held up as far as I knew. Out of frustration I started popping the plunger in and out with my thumb until it suddenly shot out and hit me in the chest like a chestburster from Alien, praying me in the face with a fine mist of old brake fluid. Problem solved.
IMG_0646.jpg

There was a ring of hardened gunk from years of grime running through the clutch. I thought it was rust, but after carefully scratching it with a screwdriver I realized it was just gunk and I carefully widdled it away, being careful not to scratch the bore. The master was also full of crap. I used a t shirt on the end of a flat head to clean everything out. Ended up with a good looking bore, so I knew I was in business.

I stuck the new plunger in, reinstalled the c- clip, and bolted the master back up, reinstalled the line and heat shield and bled it. No issues, so far, everything is staying squeaky clean and works like a charm...

Anyway, I hope this helps someone out! It ended up being a really simple job, but as a former FJ40, FJ60 and FZJ80 owner, the vacuum system was a bit of a mystery to me. After learning about the system, it's really quite simple, but unusual in context of the other Toyotas I've owned.
 
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