Clutch Booster Question

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LS1FJ40

LS1FJ40

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So, this may seem like a silly question. Is the clutch booster necessary? Can I just bypass it? I can't imagine that the clutch is so heavy on my LJ71 that a booster is necessary.

The reason I am asking is that I have replaced my master cylinder and it is taking in air in the system somewhere. All new hoses. The slave cylinder is still original but my understanding is that it isn't likely that this could be the problem. I have ordered a slave cylinder and going to replace it.

Any suggestions.

Symptoms: Replaced master cylinder Friday evening. Bled the line. Drove it and it was fine. Truck sat all day Saturday until about 8pm. I hopped in, pushed the clutch to the floor, stuck there. I pumped the clutch about 40 times and got pressure. Drove it and it needed to be pumped every few times. Any suggestions?

Thanks.
Jeff
 
I replaced the clutch master. I'm not sure I understand how it could be leaking out the back. Where the rubber boot is?
 
LS1FJ40 said:
I replaced the clutch master. I'm not sure I understand how it could be leaking out the back. Where the rubber boot is?
Click to expand...
Where it bolts to the booster. You might not see the fluid, as it could be held in there
 
I'm not losing any fluid out of the reservoir. It's weird. The pedal will stay at the floor after the first push after sitting overnight. After that it's normal but sometimes I have to pump the pedal to shift.
 
Sounds like the system just needs a thorough bleeding.
 
I will give it another go with bleeding it. See if that helps. Thanks.
 
OK. Out of curiosity what would the new fluid mean? Do you think there is something wrong with the fluid that was in it?
 
Ok. So, I bled it again using new fluid. Pumped up and had pressure. Let it sit for about 3.5 hrs. Pushed pedal and it stayed down. Didn't rebound. So, I pulled the master cylinder off to see if there was fluid behind it. Nothing. So, I guess I'm at the point of replacing the slave. Anyone have a part number for it?

Also, is the Clutch booster necessary? The purpose is to make the clutch easier to push in correct? I'm 6'1" 240lbs. I can't imagine that I wouldn't be able to push in the clutch without it. I was thinking about bypassing it to see if it is somehow the problem before I pull the slave off.
 
I've replaced it twice. It could be that they are not OEM JDM masters. I'll order OEM. I know better. I originally bought the Duralast one to get me by until I got an OEM one. It worked for a couple of weeks just fine. Should've ordered the OEM one.
 
Problem solved. I removed the clutch booster. Now the master runs to the slave how it was intended. Bled it. Put fresh fluid in, she shifts like butter. The clutch actually feels like how a clutch should feel. A little resistance. With the clutch booster it felt soft. Not anymore. Thanks everyone for their input.
 
Glad you solved it. I'll remember this if mine starts acting up.....
 
I drove it around town. About 60 km. Then let it sit. No issues. Shifts like new.
 
Was your booster inside the cab or in the engine compartment? How did you connect the linkage after removing the booster?
 
The booster was underneath the frame. About 2' behind the slave (towards the rear of the vehicle). There wasn't linkage. The setup was a hydraulic line from the master cylinder went to the booster, a line then went from the booster to the slave. It was about 21' of hydraulic line instead of 7'. It was a terrible setup. Then the brake booster vacuum line had a "T" that supplied the clutch booster with vacuum pressure. Eliminated the "T" and ran the hydraulic line directly from the master to the slave. The clutch is much more firm than with the booster. The only reasoning I can think is that the LJ71 was meant to be a luxury competitor to the Range Rover in JDM. They wanted the clutch to shift as easily as possible. That or maybe they thought that Japanese people are smaller and wouldn't like how hard the clutch is.

I hopped in it this morning. The clutch was firm. No pumping the clutch necessary. Drive about 45 km. no problems. I'll be removing the clutch booster completely this weekend sometime.
 
It is factory on JDM LJ71's only, I believe. It is idiotic. Day three of no clutch booster and it shifts perfectly. Best "upgrade" I've ever removed.
 
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