DIY: Master Cylinder Swap -

Scion tC 1G Drivetrain & Power Engine and transmission discussions...

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Old 08-13-2015, 06:13 PM   #1  
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Default DIY: Master Cylinder Swap


This is what I did to swap out (replace) my clutch master cylinder...

This is not the only way to do this, and I am sure that there is a better way to go about it, however, I did not find a write up on this, so I wanted to offer up this to everyone in hopes it might help.

1 - Buy new master cylinder (clutch Master cylinder) --- O' Reillys has them 33 bucks

2 - Make sure you have 10 mm wrench (there is a special kind that is specifically made for hydraulic metal hose flare nuts) or you can use a reg. 10mm wrench this is what I used. , a 12mm wrench, a 14mm wrench, a 10mm deep socket 3/8" drive, a 12mm deep socket 3/8" drive,
14mm deep socket 3/8" drive, I used at least two 3/8" drive extensions (12" each), needle nose pliers, and a set of needle nose 45 deg. long shank, 1 big bottle of Dot 3 brake fluid, or two small bottles... also a 16mm deep socket 3/8" drive, buy three hose clamps (Harbor Freight sells them) these are used to clamp off the brake hose from the reservoir and the clutch master cylinder lines from the reservoir.

3 - Use the 16mm 3/8" deep socket (or shallow socket) to remove (5) bolts that hold the drivers seat in. ** there are two bolts that are close the the tranny tunnel, which are under neath a plastic piece... remove that and there they are **

4 - Remove your seat ***** make sure your disconnect the wire harnesses and clip the zip tie also ****

5 - If you sit in the floor of your car (after removing the seat) the left side kick panel needs to be removed. (because nuts will fall behind it)

6 - Get your 12mm deep 3/8 drive socket and ratchet with a 3/8 knuckle if you have one, needle nose pliers (both reg. and long), and get under your dash above the clutch pedal.
There is a bracket that you will see the Slave cylinder piston coming from the firewall into your car, and attaching to the clutch pedal arm.

7 - Take the cotter pin out using the needle nose pliers. (this is where the piston arm connects to the clutch pedal arm)

8 - take the pin out of the piston arm fork, that holds it to the clutch pedal arm.

***** Your Clutch pedal and Slave cylinder are now separated *****

9 - Go into your Engine bay (if you have not popped the hood yet, do so now)

10 - Take your factory air box out. (should be 1-10mm screw on the intake tube, allowing you to remove the air intake and air box upper portion away) then there should be three 10mm bolts inside the air filter box bottom portion.
There is also a tube that comes out of the box and goes down into your fender, you should not have to remove that)

11 - Once this is out of the way, take your hose clamps and place them on the two lines that go to the brake Master cylinder, and on the line that goes to the clutch Slave cylinder, this will allow you to remove them with out having to worry about leaking all of your fluid out.

**** You do not have to remove the brake hoses from the reservoir or the Master cylinder if you don't want to, you CAN use a set of zip ties to hold it out of the way, however I would strongly suggest clamping off the hose from the reservoir to the clutch Master
so that you don't loose your fluid ****

12 - Once this is done, you have options... the way I did it was more than likely the harder of the choices... I will explain below....

--- You can remove the windshield washer arms, and the plastic cowling, and see if you can access the cylinder better there or not... I did not do that, I simply put my hand back there in the very tight space, and said a lot of nasty words and got it out.

--- **** Keep in mind, the hydraulic line that runs to the Master cylinder will need to be removed from the cylinder before you can remove the cylinder. ***** This nut should be a 10mm nut, and be careful if you do not use the proper wrench, you can twist, or crimp the line...

13 - Once you have the hydraulic line removed, and you also remove the black hose from the cylinder (runs to the bottom of the reservoir) you can now go back into your car...

14 - Once back inside your car, you will want to fully remove the nuts (should be 12mm) one to the upper left hand side of the clutch pedal arm mounting bracket (not visibly seen) and the second one is located to the right of the piston..

15 - Once you have both of those nuts off of their bolts, you can push on the piston rod a little bit to help break the seal that the cylinder has with the firewall, but do not try to push it out from here...

16 - Go to the Engine bay again

17 - You should now be able to pull the Master cylinder away from the firewall, keep in mind your hydraulic line is still there and so you need to be careful NOT to damage it, crimp it, or bend it...

18 - Once you have the old one out, put the new one back in its place..... then do all the steps above again just in reverse order...

************** IMPORTANT ************* ************************

Keep in mind that most Master cylinders like this are bench bled from the factory... so that means at all cost try Not to depress the piston of the new master cylinder, if you do so, you can cause air to become trapped inside the part
and will cause you to have a LARGE PAIN IN YOUR BACK SIDE when you go to bleed your system.*****************************

The final part at this point, is to make sure that everything is tightened like it is supposed to be, all the hoses are back on, and unclamped, and that you have plenty of brake fluid...

19 - Bleed the system.

This part I will HIGHLY recommend that you find another source because at the moment this is where I am at, and am not having a ton of luck....

USUALLY...all you do is simply pump the clutch pedal a few times, and then depress it to the floor, leave it there... open the Slave cylinder bleed valve and let out the air / fluid, then close the valve, and pull up on the clutch pedal, depress it again, etc. until you have your clutch pressure, you will need to KEEP AN EYE on the fluid level in your reservoir so that you do not go dry and suck air into your system from there. You MAY OR MAY NOT have to adjust your engagement piston, that also is another topic that I am not going to say do it this way or that, because there are some exact specifics I believe that need to be followed or it can cause issues.

As always, any comments or questions are welcome.

Keep in mind, I am not stating that this is the only way to do this, I am just offering up the way that I did it in hopes that it might help someone else do the job easier or faster.

Last edited by MR_LUV; 01-10-2018 at 11:39 PM. Reason: typos, spelling
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Old 08-16-2015, 10:34 PM   #2  
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Nice write up..I did this procedure 4 times ugghh...1st was a PITA...but after that,was pretty easy, least for me

Last edited by MR_LUV; 01-10-2018 at 10:55 PM. Reason: typo
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Old 01-10-2018, 11:29 PM   #3  
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Nice DIY article!

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Old 03-04-2018, 06:59 AM   #4  
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speaking of master cylinder, if you have an upgraded clutch/pressure plate and your wondering why you keep killing master cylinders, your not alone!. I replaced mine 4 times before i finally said enough was enough and did some research. Found out its not the master cylinder itself that's junk, its the clevis (the piece that connects the rod to the back of the pedal). theyre junk and bend under pressure and eventually cause the rod to either not go in all the way (clutch not engaging) or they cause the master cylinder to leak fluid all over your foot. thankfully, Twos R Us makes a solid clutch clevis out of solid steel for an MR2 that fits our cars. solves the problem immediately. clutch feels brand new, no play and no low engagement. Heres the link.
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