Clutch master cylinder install

[bvallerand]

How to change the clutch master cylinder in a 1998-2001 Subaru Impreza 2.5rs
A tutorial by: Ben W. H. Vallerand
The clutch master cylinder is a vital part of the clutch system on your car. It is the unit that transfers the direct input of your foot on the pedal to the hydraulic pressure that releases the clutch. Over time the seals in the clutch master cylinder wear out and create inconsistent clutch and pedal action and excessive play in the clutch pedal. In the long run this can lead to premature clutch failure and possible transmission damage. These instructions will walk you through, step-by-step, the process of replacing a worn out clutch master cylinder and properly bleeding the clutch system on a 1998-2001 Subaru Impreza. Replacing your own clutch master cylinder can save you a significant amount of time and money.
Conventions: Warnings will be noted with the word WARNING in RED. Helpful hints will be noted with the word HINT in green.
Skill Level: This project can be easily undertaken by someone with a general knowledge of automotive mechanics.
Time: Less than 1 hour
WARNING: Improper installation of the clutch master cylinder and/or improper bleeding of the clutch hydraulic system can cause damage to the clutch and transmission.
Disclaimer: All modifications to your vehicle are done at your own risk. Carefully read all instructions before proceeding. If you are under 18 we recommend the assistance of a parent or guardian during this process.

Image courtesy of Rockauto.com
Materials and equipment needed:
• Replacement clutch master cylinder
• 3/8” drive ratchet
• 3/8” extension 6” long
• 10mm & 12mm sockets 3/8”drive
• Needle nose pliers
• 8mm open end wrench or line wrench
• Flat head screwdriver
• ½ quart DOT3 or DOT4 brake fluid
• Brake cleaner or similar to clean spilled fluid and any fluid that might have been leaking from the bad clutch master cylinder
• Brake bleeder catch bottle
• Energy Drinks or similar to aid in focus (WARNING: Energy drinks can cause complications in young children and individuals with heart problems. Do not consume if you are under age 16 or have a heart condition.)
• A cold 24 pack of Coors Light™ (WARNING: Consumption of alcohol can impair your judgment. Do no drive after consuming alcohol. Do not consume alcohol if you are underage or it is illegal in your region.)
• A friend to help you bleed the hydraulic system



IMG 1 (materials)  
Instructions: Removal
1. Start by removing the negative battery cable from the battery.
(WARNING: Do not touch the positive battery terminal or do any work on your vehicle without disconnecting the negative terminal. Failure to comply can lead to electric shock or damage to the vehicle.)

IMG 2 (Disconnect battery)

2. Remove the air box to allow better access to the clutch master cylinder.
a. Remove the 3 hoses marked by Yellow (The hoses can be removed by pulling on them with your hand)
b. Remove the 2 flat head band clamps marked by Green (The band clamps are unscrewed to loosen)
c. Remove the 10mm bolt marked by Orange and place in a small parts tray or cup.

IMG 3 (Air box removal)
3. These next few steps are to make sure that you have enough room to remove the clutch master cylinder.
a. Using the needle nose pliers remove the vacuum line running from the brake booster to the intake manifold marked in Orange.
b. Using a flat head screwdriver, carefully release the clip holding the wiring harness above the clutch master cylinder marked in Green. Then the harness can be pulled below the clutch master cylinder.
c. The A/C line marked in Blue is held in place by a single 10mm bolt just off screen to the left. Remove the bolt and carefully pull the line down allowing enough clearance to easily access the clutch master cylinder.

IMG 4 (Making room)

4. Under the dashboard: The pin connecting the clutch pedal assembly to the clutch master cylinder (circled in Green) is held in place by a codder pin and a plastic clip (remove with needle nose pliers) and place the pin and codder pin in a small cup or parts tray.

IMG 5 (Under dash)


5. Using an 8mm wrench loosen the hard line connected to the clutch master cylinder.
HINT: The connectors on automotive hydraulic hard lines and made of soft low-carbon steel and are prone to corrosion, stripping and breaking. If the connector looks corroded spray it with some WD-40 or similar penetrating oil. When attempting to break the connector free; first tighten it just slightly to break it free and then loosen it. This will greatly reduce your chances of breaking it off.

IMG 6 (Line removal)
6. Place something under the line to catch the small amount of fluid that will fall from the master cylinder. The cap from a spray paint can works just fine. Carefully push the line to the side.

IMG 7 (Fluid catch)
7. Using the 12mm socket and an extension remove the two nuts holding the cutch master cylinder to the firewall. The clutch master cylinder should easily pull away from the firewall. (Note: your clutch fluid will most likely be clear or brown. Mine is high performance racing fluid which is why it is blue.)

IMG 8 (Nut removal)

8. Thread the nuts back onto the studs so you don’t lose them and use the brake cleaner to clean the fluid that leaked from the master cylinder on the firewall as well as the surface that the new master cylinder will mount on.

IMG 9 (Empty mount, cleaning needed)
Old vs. New: This is what the old clutch master cylinder looks like disassembled next to the new one. The two black rings on the white piston are what seals the fluid in and what wear out over time. If you notice the only difference between the two master cylinders is the shape of the reservoir and the new one has a bleeder screw on the end of it to allow for better bleeding of the clutch system.

IMG 10 (comparison)
Instructions: Installation
9. Make sure to adjust the end of the new clutch master cylinder to the same length as the old one. (WARNING: Failure to properly adjust the end of the clutch master cylinder can result in bottoming out or over stroking of the clutch master cylinder damaging the part.)

IMG 11 (Adjust end)


10. Install the new clutch master cylinder in same way you removed the old one.
a. Seat the clutch master cylinder onto the two studs sticking out of the firewall and tighten the nuts up snug, aproximately 20-30ft/lbs. (WARNING: Overtightening the nuts can either strip the nuts or break the studs causing you a lot more work and a large head ache.)

IMG 12 (New M.C. mounted)
b. Make sure the threads are clean on the fluid line connector. Insert the hard line into the new clutch master cylinder and tighten it down with the 8mm wrench. Again be careful not to over tighten because these connectors are prone to snaping.
c. Connect the clutch master cylinder arm back to the clutch pedal assembly under the dash.

IMG 5 (Under dash)
11. Fill the reservoir to max line with fresh dot 3 brake fluid from a sealed container.

IMG 13 (Fill reservoir)
Instructions: Bleeding

12. Attach the brake bleeder catch bottle to the bleeder nipple on the clutch master cylinder.
a. While your friend puts light pressure on the clutch pedal loosen the bleeder screw ¼ of a turn to the left. Air and fluid will exit through the line. The pedal will fall to the floor, as it does close the bleeder valve so air does not re-enter the system.
b. Have your friend pull the clutch pedal back out and repeat step “a” until fresh clean fluid is coming out without any air bubbles. You may need to refill the reservoir a few times during this process.

IMG 14 (Bleeder bottle hooked up)


13. Next move to the slave cylinder. Attach the bleeder bottle to the slave cylinder bleeder nipple. Repeat the bleeding process explained in step 12a with the slave cylinder until fluid is coming out clear and free of bubbles.

IMG 15 (Bleeder hooked to slave cylinder)


14. When you are finished bleeding the system make sure to top off the fluid in the reservoir. Check over everything you have done make sure all nuts bolts and connectors are tight. The clutch pedal should now feel much more consistent and solid. Start the car up and try to shift into gear making sure the clutch disengages all of the way. If the transmission grinds you may have to re-bleed the system. Take the car for a test drive and enjoy your clutch acting the way it should.

[bvallerand]

Please let me know what you think of the instructions. I have to use them for a class and also have to do user test results.

[sd70feb]

i wish every write up was like this......good info,tips, and pics so i can actually see what im dealing with.... great job man...

[URABUS]

Originally Posted by sd70feb

i wish every write up was like this......good info,tips, and pics so i can actually see what im dealing with.... great job man...

+1

Great write up! My only input would be that you may want to add a caution on step 12 to be careful not to push the pedal all the way to the floor while bleeding. There is always the possibility that with the bleeder open, if the pedal is pushed too far, you may over stroke the master cylinder thus damaging your new one. Just my .02, take it or leave it.
-Shawn-

[bvallerand]

i was unaware of that being an issue Shawn. I read that if you bench bleed it there is a good chance of over stroking it but i thought once it was hooked up properly it could only go so far.

[URABUS]

I know that with brake systems, it is still a possibility to over stroke the master when bleeding calipers. I could be incorrect since you have the adjustment on the plunger lever. I would have to get under my dash and look, the clutch lever may have a stop on it and you may be only going that far no matter what. It would be more of a possibility to over stroke on a bench bleed if you weren't careful, since the stroke isn't being controlled. It is always a good idea to do a bench bleed though, although it doesn't necessarily have to be done on a bench. You could do the same thing with the lines plugged and the master in the car. Just hook it to the pedal and stroke the pedal. Excellent job though.
-Shawn-

[bvallerand]

i had always been told to bench bleed BMC's literally by hand till you bottom it out. The CMC came with instructions that said dont bench bleed because it will damage. i havent done a BMC in a long time so i could be wrong. The last one i did was in HS and my autoshop teacher told me what to do lol. He was a crazy old drunk.

[bvallerand]

BUMP because everyone needs to know how to do this and it makes me feel good!

[SubyRS1]

Excellent DIY bvallerand ! But you need to add "DIY with pics" in the title to draw attention to it. I did a search and there were six possibles and yours was the last one I looked at actually. And the only one with the right info.

Thanks for taking the time to make this topic. I am waiting for my clutch master and slave right now (Rock Auto rocks) and I was dreading stuffing my head under the dash backwards with my bad back. The simplest things just plain hurt for days. It turns out that I was looking at the wrong place under the dash. I did not notice that the pedal pivot shaft went over to the right and then into the firewall. You pictures made it clear as day. You just made my day because that connector is very easily accessed.

I am doing a clutch replace DIY right now and I have 107 pictures to go through. Thanks again!

[Spec R]

thanks for the DIY.

i would change one thing though. I would recommend 8mm line wrench ONLY. Stripped line bolts are the worst.