4th Gen Clutch Dampening Delete (Master & Slave)

So after reading up on the clutch damper delete on the 5th gen LGT, as well as on the STi, I decided to take a crack at this on my car.

I'm not sure which other models this applies to, but I performed this on my '07 spec.B. I imagine it'll apply identically to any of the '07-'09 spec.Bs, but anything with a 5MT may be a bit different (since the slave cylinder is most likely different). I'm sure it's a similar procedure for those, however.

A quick overview on the procedure... there is a fluid damper built into the bottom of the clutch master cylinder (as an EE, to me it's best described as a fluid "capacitor"). Additionally, there are restrictive elements in the slave cylinder (best described as a fluid "resistor"). Removing both of these should give the clutch pedal a much more linear and predictable response.

The overall method is to remove both the master and slave cylinder, remove the damper from the master cylinder and replace it with a plug, and then remove all of the restrictive elements inside of the slave cylinder.

The only thing you should need to purchase (short of any tools) is a drain plug to replace the damper. My master cylinder (and I imagine all of them that have a damper) uses an M16-1.5 thread. I used this oil drain plug, part number "NOE 7043003" from NAPA Auto. Everything else involves tools, brake fluid, and some time/patience. I ran into a couple annoying parts, which I'll chat about in the step-by-step.

As for results, the difference is significant. The clutch pedal feels slightly lighter at the top of its travel (when you start to depress it), and engagement now happens MUCH sooner than before. My car has, I believe, a stage 1 South Bend Clutch, so I'm not sure if the difference is more or less noticeable than the stock clutch/other clutches. Engagement always occurs at the same point very close to the floor, no matter how quickly or slowly I release the clutch. It feels much more linear and predictable than it did before the mod. I'd absolutely recommend it, just like anyone else who has written about this for other cars.

Let's get down to the procedure! Note that if you don't intend to modify the slave cylinder, you can skip removing the intercooler mounting bracket and the starter.

1. Hop in the car, remove the plastic piece under the dash for some space (3 plastic clips), and then unhook the clutch master cylinder from the pedal assembly (it's above the pedals, between the gas and brake pedal). Getting the pin off can prove to be a major PITA... I eventually just pried it off and broke the plastic tip off of the pin since the snap pin holds it in well enough as is.
   http://i986.photobucket.com/albums/ae347/bvallerand/UnderDashcroppedandlabeled.jpg
   Above picture of the area you're looking for taken from this thread at RS25.
    
   http://i.imgur.com/TkDX63y.jpg
   Here's a picture of the pin with the plastic part broken off, and the snap pin
   
2. Disconnect the negative from the battery.
   
3. Remove the engine cover and intercooler (you don't need help yet... right?)
   
4. Remove the intercooler mounting bracket, for space (two 12mm bolts).
   
5. Remove the starter: disconnect the electrical connector (just slides off), then remove the 12mm nut and washer holding the positive connection on. Then remove the bolts that hold the starter to the bellhousing (two 14mm bolts). This can be a bit tricky, but doable from the top. Use the right set of sockets/extensions to make your life easier. You might need to move some hoses out of the way.
   
6. Drain and remove the clutch master cylinder. I used my trusty Harbor Freight brake bleeder/vacuum pump to empty the reservoir, and then drain the main cylinder through the bleed nipple (8mm nipple). After draining, remove the hard line running to the MC (10mm bolt). Be careful with this, it's generally on there pretty tight. I used a full-size spanner instead of the midget spanner to allow me more torque without the chance of stripping the head of the nut. Once the line is removed, unbolt the MC from the firewall (two 12mm nuts), then pull the MC away from the firewall and put it aside.
    
   http://i.imgur.com/oZDhEen.jpg
   Hard line removed. Note the shop towel used to catch any residual fluid.
    
   http://i.imgur.com/iIOlbz5.jpg
   Draining the MC.
   
7. Next up, the slave cylinder. First, unhook the spring from the release lever and set it aside. Then, remove the banjo bolt (14mm) on top of the slave cylinder (and don't lose the two washers around it!). Have a couple shop towels around to soak up residual brake fluid in the line. Move the line aside, then unbolt the slave cylinder from the transmission (two 14mm bolts).
    
   http://i.imgur.com/ZVWp71a.jpg
   The slave cylinder, the banjo and both mounting bolts visible.
    
   http://i.imgur.com/0AQH9jo.jpg
   What has been removed at this point!
   
8. Now it's time to remove the damper from the MC. I figured it'd be easy... should just screw off, yeah? After trying by hand, by applying heat to the MC body, by using vice grips, the final solution ended up being a bench vice to grip the damper, another vice/clamp to grip the MC body, and all of my strength to finally break it free:
    
   http://i.imgur.com/8Ca1H3G.jpg
   Thanks, UMass!
    
   http://i.imgur.com/C09PFbr.jpg
   The MC, the new plug, and the damper.
   
9. Now, replace the damper with the oil drain bolt. I discarded the gasket that came with the bolt and reused the gasket that came off with the clutch damper. I sprayed the gasket with some Permatex Copper Spray-a-Gasket to ensure it would seal, but chances are you'd be fine without it. Torque the bolt down as tight as you can reasonably tighten it (17mm bolt head). You're done with the damper delete!
   
10. On to the slave cylinder. Removing the rear 24mm bolt seemed to be impossible without a vice or something similar. In the end, I ended up using my impact gun to break it loose (I used a 1" impact socket, since I don't have a 24mm impact socket). After removing the bolt, out should come an o-ring, a metal plate with a rubber washer on it, a plastic piece, and a spring.
     
    http://i.imgur.com/b5g3F8O.jpg
    Rear bolt removed, thanks Ingersoll-Rand!
     
    http://i.imgur.com/aXZNuKl.jpg
    http://i.imgur.com/zU644sM.jpg
    Slave cylinder internals.
     
    http://i.imgur.com/eOh6sid.jpg
    Orifice plate in the slave cylinder, from the side that faces the SC piston.
     
    http://i.imgur.com/agM3zjU.jpg
    Orifice plate, from the side that faces the rear of the SC, with the rubber washer removed.
     
    http://i.imgur.com/MBhkOfC.jpg
    Plastic piece, from the side that faces the SC piston
    
11. At this point, it's a good idea to clean up/rebuild your slave cylinder if you want. Pull the piston, clean off all the dirt/grime/grease on the pushrod, clean everything else with fresh brake fluid, and rebuild it. I added grease between the piston and the push-rod, which I think is a pretty good idea if you're planning on rebuilding the slave cylinder.
     
    http://i.imgur.com/ZoiiPUQ.jpg
    http://i.imgur.com/bf0kkdB.jpg
    All cleaned up!
    
12. Reassemble the slave cylinder without the spring, the plastic piece, or the metal orifice plate. The only thing that should be in the rear side is the o-ring and the 24mm bolt. Tighten it as best you can (I just used the impact again). At this point, I'd fill the slave cylinder bore up with plenty of fresh brake fluid, then insert the piston from the front end. Tilt the slave cylinder so the banjo-bolt hole is vertical (and as high up as can be relative to the rest of the SC), then SLOWLY push the piston back into its bore until fluid starts coming out of the banjo bolt hole. If you put in enough fluid, then as the spring returns the piston to its fully extended position, there should be a little bit of fluid still in the banjo bolt well. Make sure to keep the SC upright at this point onwards until it's installed into the transmission (this will ensure that it's fully bled from the start!).
    
13. Bring the SC back to the car and re-attach the banjo bolt along with the two washers (14mm bolt, torqued to 13ft-lb) to the SC.
    
14. Reinstall the MC back to the firewall (two 12mm nuts, torqued to 13ft-lb). Insert and tighten the hard-line into the MC (10mm nut)
    
15. Now it's time to fill/bleed the clutch system. The process was painless for me with a vacuum bleeder. I attached the bleeder to the bleed nipple on the SC (8mm bolt), set the SC down in the engine bay such that the bleed nipple was the highest point of the SC, then added fluid to the MC and applied vacuum while opening the bleed nipple on the SC. The vacuum will pull fluid from the MC through the system into the drain bottle of the vacuum system. I only applied at most 5psi of vacuum to ensure I didn't stress anything, and waited for it to drop to 0psi before pumping again. Keep the reservoir topped off during this process. When clean brake fluid starts filling the bottle, you're done bleeding, and can close the bleed nipple on the SC, then reinstall it to the transmission (two 14mm bolts, torqued to 30.2 ft-lb). Make sure to apply grease to the contacting surfaces between the push-rod and the release lever! Finally, reattach the spring to the release lever.
     
    http://i.imgur.com/5k01f2w.jpg
    http://i.imgur.com/uKQUriQ.jpg
    Filling/bleeding process
    
16. You're pretty much done! Reinstall the starter (two 14mm bolts, torqued to 37ft-lb) to the bellhousing, then reattach the electrical connector and the positive lead and the corresponding washer/nut. Don't forget to attach the ground bracket along with the top 14mm bolt on the starter!
    
17. Reattach the intercooler mounting bracket (two 12mm bolts), then the intercooler.
    
18. Reattach the MC pushrod to the clutch pedal. Make sure to grease the pin before installing it. Re-insert the snap pin.
    

You're done!

Very nice work and very nice write up Shamit. :::thumbsup:::

Thanks!

Anyone with a 5MT LGT/Outback wanna chime in on what (if anything) needs to be done for their slave cylinder? You know you want this ultra-responsive clutch pedal...

Im very tempted to try this. What difference have you noticed?

As for results, the difference is significant. The clutch pedal feels slightly lighter at the top of its travel (when you start to depress it), and engagement now happens MUCH sooner than before. My car has, I believe, a stage 1 South Bend Clutch, so I'm not sure if the difference is more or less noticeable than the stock clutch/other clutches. Engagement always occurs at the same point very close to the floor, no matter how quickly or slowly I release the clutch. It feels much more linear and predictable than it did before the mod. I'd absolutely recommend it, just like anyone else who has written about this for other cars.

It's a minor, but very significant difference. My shifting is much more consistent now.

Holy crap this is fantastic. I never even considered the fluid resistance leading to the less then ideal clutch feel. Any idea of my light weight flywheel impacting the engagement without the added factory resistors?

I'd imagine a LWFW would make your clutch feel a little more sporadic and grabby with the dampeners in place, since the lower mass (i.e. lower rotational inertia) of the LWFW would make it more sensitive to an inconsistent pedal.

Bump. Anybody did this with their 5MT? I am quite sick of the non-linear response of the clutch engagement feel.

You can be the first

covert doesn't have a spec b, does he? i was pretty sure he's done both, but maybe i'm mistaken...

edit: halfway...

(post 825 in his build thread)

https://r.tapatalk.com/shareLink?url=http%3A%2F%2Flegacygt%2Ecom%2Fforums%2Fshowthread%2Ephp%3Fp%3D5568939&share_tid=218363&share_fid=5383&share_type=t&share_pid=5568939

Bump. Anybody did this with their 5MT? I am quite sick of the non-linear response of the clutch engagement feel.

Haven't done this damper removal, but something else that helped my shifting and clutch engagement a lot was installing the Whiteline rear diff insert bushings. I was surprised at how much better and more direct the clutch pedal felt. Removed a whole lot of the 'rubber band' like effect while shifting. With the bushings, and this damper removal, I bet you could perform surgery with the clutch pedal

covert doesn't have a spec b, does he? i was pretty sure he's done both, but maybe i'm mistaken...

 

edit: halfway...

 

https://r.tapatalk.com/shareLink?url=http%3A%2F%2Flegacygt%2Ecom%2Fforums%2Fshowthread%2Ephp%3Fp%3D5568939&share_tid=218363&share_fid=5383&share_type=t&share_pid=5568939

Nice. So am I to understand that the internal of the slave cylinder are slightly different (compared to the 6spd) or exactly the same? Not that bad of a job really.

In any case, it does not matter now that I just saw the pics from covert.

With the bushings, and this damper removal, I bet you could perform surgery with the clutch pedal

I went ahead this evening to swap that dampener with the oil drain plug bolt on our 05. Drained the fluid and took out that dampener off no problem. When it was time to put the oil drain plug, I then realized that the one I had was too big . Looks like the required oil drain plug for this mod is the later version.. Dang it! Have to go and grab that bolt tomorrow.

Also, I am realizing that our slave cylinder is different than the one you have OP. It looks like I cannot modify it; I don't have that 24mm bolt.

@bonbon the early cars only had the dampener in the first reservoir. The later ones had two for extra special clutch gooiness.

Still need to do this to mine....maybe a this weekend project.

Even my wife who is currently learning how to drive, she was able to master it very quickly. So, we may not have to get a car with an auto after all

win-win!