Manual S-10 master cylinder fail

[87geeinn]

I bought a new (reman) manual S-10 brake master cylinder, bench bled it, and put it on the car with a custom length pushrod. Just a minute or two as I started to bleed the brakes, I heard a "clink" as the pedal was coming back up and looked under the dash to see that the pushrod had lost it's seat because the master cylinder piston did not return to full stop. It even stayed this way until I pulled it off of the car and put it in a bench vise to take a picture. Now, I can't for the life of me think of anything I did incorrectly, although I'm not ruling out operator error. However, just an FYI, that IF there are bad reman units out there floating around, you other fellas running this same set-up should be aware of this potential problem. FYI, I bought this unit (Part #10-1905) from Advance Auto Parts and the box had a sticker indicating that it originated from a company called OEM (Original Equipment [Re]Manufactured):

 

[87geeinn]

See attached pic and video. The video depicts how the piston is binding inside the shaft and picture shows the signature marks where the piston is scraping the inside bore. There was also some debris in the form of fine metal flakes that was gathered up on the brass-colored piston, just to the left of the scrape marks on the bore. I'm not sure how this happened, but whatever the cause, this just goes to show that it is possible to have the pushrod fall out of the back of the master cylinder with no positive way of holding in there.



[video=youtube;COJIg9dptdQ]http://www.youtube.com/watch?v=COJIg9dptdQ[/video]

 

[LSJM1]

You need the pushrod cup that comes on the s-10 it holds up the pushrod and will not let it lose contact with the master I tried an s-10 manual master setup,cut and welded the pushrod to the right length I took it off the car and went back to power brakes after driving on the street for about a week I learned that I like to be able to stop it was not worth the little bit of weight savings I guess for a track only car I could live with it

 

[Nick Micale]

I has been a while since I installed a S-10 MC on a GN, but I used a rubber boot, maybe the one off a Powermaster, that fit on the end of the MC and kept the rod from falling out if the pedal retracted further than normal.

As far as the MC being bad, since the application is for cars/trucks almost 20 years old, wonder how long it has been on the shelf?

 

[charlief1]

Everyone wonders why I don't use a remanned master and this is one of the reasons. I haven't had a remanned on that was worth a crap in over 20 years. Get a new one and you should be good.

 

[87geeinn]

You need the pushrod cup that comes on the s-10 it holds up the pushrod and will not let it lose contact with the master I tried an s-10 manual master setup,cut and welded the pushrod to the right length I took it off the car and went back to power brakes after driving on the street for about a week I learned that I like to be able to stop it was not worth the little bit of weight savings I guess for a track only car I could live with it

I looked around but my only hope of finding that cup and pushrod is a junkyard and there just aren't that many around here. I am doing the next best thing and affixing a large freeze plug to the back of the master cylinder with a hole drilled in the center. The outside diameter of the section of the master cylinder is 45mm and the freeze plug is 43mm. I'm going to bore out the hole in the pedal/powermaster adapter for everything to fit through there and that should do the trick. As far as the pushrod, I cut the ring off of the powermaster rod and bought some 3/8" rod stock that I am going to have welded to the end of it. I will take pictures when I'm through.

As far as the MC being bad, since the application is for cars/trucks almost 20 years old, wonder how long it has been on the shelf?

Who knows, the same thought went through my mind too. I peeled the "OEM" sticker and there was a Cardone sticker underneath that one. Makes you wonder what is going on behind the scenes doesn't it?

Everyone wonders why I don't use a remanned master and this is one of the reasons. I haven't had a remanned on that was worth a crap in over 20 years. Get a new one and you should be good.

You're absolutely right. I've already ordered a new unit. FWIW, after I took the cylinder off of the firewall to drain the fluid and put it back in the box for a return, I already noticed some crud at the bottom of the reservoir even though I was as meticulous as possible when bench bleeding the thing and starting the bleeding process. I bet that the internals looked like $hit from the get-go.