Clutch Master- Rebuild / Mod

[yxmj]

Just a quick walk through on how easy it is to rebuild/repair a master cylinder.

 

Determine if it is your master cylinder…..If you have leakage in the cab over the fuse panel….YES

 

No leakage but soft clutch …or you have to double or triple pump to get clutch… take off the MC reservoir lid…press on the clutch…..does the fluid rise in the reservoir and/or do bubbles come out? If so then.....Yes

 

To be sure remove the exit line (shown in the pick below with a red arrow) …….place a rag to catch any spillage and push the clutch down……is there a strong blast of fluid shooting out…..if not then…..YES

 

Rebuild kits are available….but unless you have leakage in the cab you might not need one.

 

If you have determined the master cylinder is bad ….you have to remove it anyway…take a couple of minutes and see if you can’t do this quick repair/modification before you shell out $$ for a new one.

 

Removal/Repair/Modification

 

Tools required-

7/16 Wrench

½ wrench

½ socket with extension and ratchet

Snap ring pliers

Flat screw driver

Air compressor

 

If you have fluid left drain it out….I use a clear plastic Turkey baster that will suck it all out with a couple of pumps….if the fluid is new and clean some might what to re-use it.

 

This is a YJ but the position mounting and proceedure are the same.

 

To make removal easy I like to take off the reservoir (bolt with blue arrow) Then a 7/16 for the line fitting (red) and the two mounting nuts….the bottom one is a stud in the fire wall and easy to do…the top is a bolt (why not a stud again?) that you will have to get at under the dash with a 8” extension ½ socket and ratchet. While you are under there you will see the clutch rod is attached to the clutch pedal bar with a cotter pin and a plastic washer….just pull the pin remove the bar and the whole assembly will pop out

 

 

First order of business is a snap ring that holds the whole assembly in (Pic 2 red arrow) Snap ring pliers and a small flat screwdriver make quick work of it.

 

 

Ok, this part is tricky and I do not what anyone to hurt themselves or others….of the dozen or so that I have done I have only had 1 that the inner assembly slide out with a couple of taps on the work bench….try that first….if not…

 

Use a clamp or vise and clamp a block of wood or piece of metal over the reservoir hole (plastic reservoir off)….Now place a coffee can or pail full of rags as a “Catcher’s Mitt” to get the inner assembly when it comes out…..Using a compressor with an air gun slowly start to shoot air into the opening that the line screws into. Now I can pop it out easy just by controlling the air with my blow gun….but the first time resulted in a shotgun blast that gave me a blood blister on my thumbnail that lasted 5 months and a permanent dent in the tool box!!!!! Be smart and careful!!!!!

 

 

So now you will have the whole assembly apart . On the exploded diagram below look at #14…. The valve stem retainer. It is a silver cap with a hole in the lid and 2 small tabs that are bent in…you will have to carefully insert a flat screwdriver and bend these out slightly to allow you to fully disassemble this (then you bend them back in during reassembly)

 

 

Here is where the repair/mod comes in….look at the exploded diagram Above…..the culprit is the small spring labeled #11….it sits in the spring retainer cup…its job is to allow #9 the stem tip seal to move back when your foot is off the clutch, this lets fluid from the reservoir into the cylinder and then when you press the clutch it “plugs” the hole and forces the flow to go out the line down to the slave and activate the clutch.

 

 

 

Almost all I have opened the spring is toast (in one I could not even find it????)…you could replace that spring or try this.

 

The first time I did this I used a normal ballpoint pen spring….but when walking though one of our hardware stores (Called Princess Auto…..I think it would be comparable to Tractor supply or the like) I found a bag of surplus springs….for $2… that had a larger version of the ball point spring in it so I use these.

 

 

As you can see in Pic 6 below…instead of installing the spring in the cup….I install it behind the cup on #10 the valve stem (in that pic you can see a normal ball point pen spring alongside one of the others (top one)….The pen spring will work…you can even stack 2 together if you put a small washer in-between…or hunt down a larger one.

 

 

Now just re-assemble in reverse order……before I install I bench test by simply adding liquid and pressing the plunger…you should now get a “Super Soaker” strength stream out of the line out hole.

 

Re-install and good luck. :thumbsup:

 

*****NOTES*****

 

This MC was an aftermarket one that had been replaced at one time (I am assuming it is a “Doorman” because the exploded diagram I used I found on the web, it was labeled doorman, but I got it off a Honda web site.) There are other types out there….from the factory they could have been NABCO….and there are NABCO replacements….If yours is a Nabco you might be even luckier…..the process is the same but as seen in the pic below the NABCO uses a metal spring cup, which is not only stronger than the plastic but it will allow you to use an even bigger spring.

 

 

 

****If you have a newer MC with the permanent line to the slave look at the end with the connecting rod….if it has a snap ring this would be a possible solution for you.******

 

*****If you are experiencing leakage in the cab you will have to obtain a rebuild kit…..the procedure is the same but you would replace the 2 rubber seals on the piston with the new ones in the kit (IMHO if it is this kind of rebuild I would consider a new MC as I have yet to find a rebuild kit under $30)*******

 

Maybe this can save you some Time and $$ (I know that after I did this for the first time I went to the back shed and dug out about 4 or 5 MC’s that I had changed over the years and went through them all for repair and or parts!) :thumbsup:

[Comanche County]

Great info!

 

:thumbsup: