Service Bulletin: Hydraulic Clutch Master Cylinder

The hydraulic clutch master cylinder used on the 02‐06 Acura RSX, 02-05 Honda Civic Si and 04-08 Acura TSX have a feedback plate that is known to fail after installing a performance clutch with a higher release load than the factory pressure plate. ACT engineers have researched this problem and recommend replacement of the original equipment master cylinder with one from a 2001 Honda Civic (Honda part number 46920-S5A-G05). This earlier master cylinder design is a direct replacement, does not have the feedback plate feature and installs without any other modifications. The factory feedback plate is intended to increase driver comfort by softening clutch feel, yet it does not decrease maximum pedal effort. There are no performance drawbacks to running without it.

If you have any questions please feel free to contact our technical service department using the information provided below.

Advanced Clutch Technology, Inc.

206 East Ave K‐4

Lancaster, CA 93535

Phone (661)940‐7555

Fax (661)940‐7541

20 thoughts on “Service Bulletin: Hydraulic Clutch Master Cylinder”

  • […] feedback plate which seems to be a weak point. I also saw a bulletin by ACT that describes this: Service Bulletin: Hydraulic Clutch Master Cylinder / ACT News // Advanced Clutch Technology Also, Hybrid Racing offers an Civic EM1 clutch plus a braided line for the 8th gen Civics- 8th Gen […]

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  • […] that the EM1 CMC fits the TSX. ACT has a bulletin that describes the EM2 CMC as a direct fit- Service Bulletin: Hydraulic Clutch Master Cylinder / ACT News // Advanced Clutch Technology If you decide to install this, be prepared to pull out the brake master cylinder and booster in […]

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  • […] did install Sat and pulled the old one out Fri night on my '06 TSX... woof. old on left, em2 on right... straight bolt up for my TSX... pretty sure it should be the same for 8th cars aswell Per ACT, they have come to the conclusion the feedback plate (triangular object at end of CMC) is to blame for failure Service Bulletin: Hydraulic Clutch Master Cylinder / ACT News // Advanced Clutch Technology […]

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  • […] did install Sat and pulled the old one out Fri night on my '06 TSX... woof. old on left, em2 on right... straight bolt up for my TSX... pretty sure it should be the same for 8th cars as well Per ACT, they have come to the conclusion the feedback plate (triangular object at end of CMC) is to blame for failure Service Bulletin: Hydraulic Clutch Master Cylinder / ACT News // Advanced Clutch Technology […]

    Reply
  • […] come to the conclusion the feedback plate (triangular object at end of CMC) is to blame for failure Service Bulletin: Hydraulic Clutch Master Cylinder / ACT News // Advanced Clutch Technology old on left, em2 on right... straight bolt up __________________ '06 | 6M | PWP | Ebony | […]

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  • […] come to the conclusion the feedback plate (triangular object at end of CMC) is to blame for failure Service Bulletin: Hydraulic Clutch Master Cylinder / ACT News // Advanced Clutch Technology old on left, em2 on right... straight bolt up __________________ '06 | 6M | PWP | Ebony | […]

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  • dong

    I recently encounter this issue with my 06 tsx with ACT's heavy duty pressure plate and my honda parts guy told me there was an updated part number (46920-S5A-G06).

    Reply
  • mike

    i had the same issue with my 03 rsx after blowing the seal outta the feed back plate twice and a bolt out of it once too bad i didnt see this service bulletin sooner but now im replacing it with and omni power cmc it dosnt have the feed back plate and also has a bigger piston

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  • Anthony D.

    Good to know that you are giving the worthy suggestions. If any problems I would face, sure I would like to know the answer from you.

    Reply
  • Aaron

    Has anyone tried JB welding the edges around the feedback plate?

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  • […] has no feedback plate and therefore you can feel the RPMs in the clutch pedal more than before. ACT recommends the older G05 revision as a drop-in. I'm not aware of who manufactures the OEM CMC so best to buy […]

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  • Jon Collins

    A friend recently had the same issue with his cylinder. Thanks for including the part number -- I'll get him to look into it.

    Reply
  • Lazaro Roig

    Does anyone offer a complete hydraulic clutch kit upgrade for 2007 civic Si sedan. Master & Slave included.

    Reply
    • advancedclutch
      advancedclutch May 11, 2016 at 7:05 am

      Since the problem is typically in the Master cylinder, most aftermarket upgrades are for just the master cylinder and not the slave cylinder. We are not currently unaware of anyone who sells a slave/master combination upgrade kit.

      Reply
  • Juan ropain

    I own a 2002 rsx type s with an stage 3 action clutch kit with lightweight flywheel , (my car is mostly stock besides that clutch) I switch out the cmc for the 2001 civic cmc and replaced the slave a bunch of times the best life i seem to get out of this cylinders is around 5 months. Any ideas? Should i go back to an oem replacement exedy clutch? Or just replace the lightweight flywheel?

    Reply
    • advancedclutch
      advancedclutch June 10, 2016 at 9:15 am

      Since we do not know what the bearing load is of the Action Clutch stage 3 it is hard to say if the switching to a lighter clutch will help the issue. We can say that our AR1-HDSS has been tested and will work with the master cylinder suggested without issue. The key is that the master cylinder suggested does not have the feedback plate like the unit that came in the RSX from the factory. The lightweight flywheel, as long as it has the proper step (UP .045"), should not affect the performance of the hydraulic system.

      Reply
  • Chris

    I have an 04 RSX-S w/ an ACT HD-SS and a Streetlite flywheel. When i first started having problems i replaced the stock CMC w/ the honda civic part in your original post. clutch pedal lost pressure again, was determined it was the slave. replaced that and now the pedal has lost pressure again. debating between omni power cmc alone, or maybe a k-tuned cmc and slave. don't know what else to do. Assistance would be greatly appreciated. thanks in advance

    Reply
    • advancedclutch

      Hey Chris,
      The first thing that we'd recommend doing is checking the entire hydraulic system for leaks and after that bleeding the system just to be sure there is no air in the lines. If the new master cylinder has failed then you will most likely find fluid leaking from the master; this could be in the engine bay or in the interior of the car where the rod comes through the fire wall. If there is no large leak from the master then it most likely hasn't failed and could be something else in the system; in which case you should continue inspecting the entire hydraulic system.

      Reply
  • Chris

    04 RSX-S w/ ACT HD-SS, have replaced the master three times now, and the slave twice. Most recently in Aug when I had a ktuned master, slave & ss lines installed. As previously stated in other post I've also tried the updated Honda Civic part and it failed also. Unless there is a particular brand you recommend I don't know what else to do. It's not my first manual transmission car, and I shouldn't have to replace these parts so much.

    Was the HD-SS a bad choice? Is there ANY other part that could be causing the clutch to continuously lose pressure? I'm at a loss, I don't know what to do anymore. I love the performance of the clutch, but cant keep dealing with the same issue every 6 months.

    Please help.

    Thanks in advance
    Chris

    Reply
    • advancedclutch
      advancedclutch March 20, 2017 at 3:22 pm

      Hey Chris,

      We're sorry to hear that you're having so many master cylinder issues. The Civic part number we recommend is for the non-SI master cylinder that does not have a feedback plate, the feedback plate on the OEM RSX design is usually where the problem lies. We have not tested the K-Tuned master ourselves so I won't be able to provide any feedback regarding that brand of master cylinder. However, we do know that many customers have had great success with the OmniPower master cylinder. Another item to check is the clutch pedal adjustment. If the adjustment is incorrect and has the pressure plate pre-loaded by the release bearing, then this can cause additional wear to you master cylinder.

      Reply
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