What's the trick with adjusting the master cylinder push rod?

[Mfr426]

Hey All, I have a 69 Charger with factory disc brakes. I think my push rod is adjusted in correctly. I've measured it and it appears to be about 3/4" away from the body. It appears that the measurement should be .92? I tried to adjust the 5/16 nut on the end but cant get it to move. Is there a trick to holding the main rod while adjusting the nut (or is the old vise grip the right tool)?

Any help would be great. My issue is that I have fluid dripping down the front of the power booster where the master cylinder meets the booster. I'm guessing that the rod is adjusted too short and causing the MC piston to come out too far?

[is_it_EVER_done?]

Your MC is shot. That's why you have fluid leaking out. It has nothing to do with the push rod adjustment. I guarantee this! Don't mess with the push rod length until you replace/rebuild the MC, I'm sure you won't have to touch the length.

[Mfr426]

This is a new MC??? I know my buddie's 68 had an issue with push rod length (car's brakes would lock up after it warmed up).

[Just 6T9 CHGR]

Mike, where did you get that spec from?   I was curious about this as well  (Ill be adding my new booster & master assy soon)

I looked in the FSM and all I found is "make sure the plunger is adjusted properly"

As far as the piston coming out too far, below the master \, in the middle, is a bolt that acts as a piston stop.

I tend to agree with is_it_EVER_done? on the maste piston seal being the problem.  What type of fluid are you running?

Im still using the DOT 3 and a leak like that is my worst nightmare

[Charger-Bodie]

quote]

just curious why arent you using dot 5 ?

[Just 6T9 CHGR]

I really dont know......when I did my SSBC conversion 2 years ago is when I should have switched.....read up on the subject and at the time I got the impression that the DOT 5 was more trouble than it was worth.   The spongy pedal issue concerned me.....

Now I think it might be too late.   can you just drain out all the old DOT 3 and replace it with DOT 5?  Wont all the older seals be damaged from the silicone (rear wheel cylinders, rubber brake hoses)

[Charger-Bodie]

I really dont know......when I did my SSBC conversion 2 years ago is when I should have switched.....read up on the subject and at the time I got the impression that the DOT 5 was more trouble than it was worth.   The spongy pedal issue concerned me.....

Now I think it might be too late.   can you just drain out all the old DOT 3 and replace it with DOT 5?  Wont all the older seals be damaged from the silicone (rear wheel cylinders, rubber brake hoses)

the dot 5 we get at napa is supossed to bw ok to mix with dot 3 ..... i personally never had the spongy pedal problem related to dot 5 there is just no way i can put paint stripper in my master cyl. we did a friend of mines 70 rr a few years ago it was one of those " ill put it together to save money " deals and when he put the brake stuff all together the little plug on the bottm of the master leaked on to the fresh apron and left frame rail needless to say we got to repaint it , not fun ever since then ive used nothing but dot  with the exception of my clutch cyl on my charger which kiesler said now way on using dot five , they call for dot 4

[Mfr426]

Chris, that .92 was from the factory service manual for 69. They have a picture of it.

When we redid the engine and bay of my buddies 68 RT we took the out for a test drive. When we got gas after a few miles of testing the brakes completely locked up. We let the car cool down and after a few minutes we could drive it fine. We ended up measuring the rod vs. the manual and sure enough it was off.

I believe I am running DOT 3. I know that I did not put any silicone fluid in the system.

[is_it_EVER_done?]

This is a new MC??? I know my buddie's 68 had an issue with push rod length (car's brakes would lock up after it warmed up).

This is not a pushrod length issue, it's a brake fluid moisture content issue. You will need to flush out all the old fluid before you try to figure out what your problem is for sure (probably just moisture leaching).

I can assure you that the booster pushrod length has nothing to do with your problem. Wether it is adjusted correctly is unknown, but it's not causing your problems.

P.S. I don't use DOT 5 either. Our MC's, Calipers, brake cylinders were not designed for it, so unless you have units that are specifically designed/rebuilt for the Silicone DOT-5, AND unless you have totally drained/flushed the existing fluid out, it is a BIG mistake to attempt to change to DOT-5.

[Just 6T9 CHGR]

I really dont know......when I did my SSBC conversion 2 years ago is when I should have switched.....read up on the subject and at the time I got the impression that the DOT 5 was more trouble than it was worth.   The spongy pedal issue concerned me.....

Now I think it might be too late.   can you just drain out all the old DOT 3 and replace it with DOT 5?  Wont all the older seals be damaged from the silicone (rear wheel cylinders, rubber brake hoses)

the dot 5 we get at napa is supossed to bw ok to mix with dot 3 .....

Really?  I've never heard of this type.   All the online articles state that you cannot mix these fluids period.  You must use alchohol to flush the system to clean it enough to make the switch.....

how have you done it?   I hope there is a fluid now that you can mix it a bit.....

Mike, how's the paint holding up on the booster with the DOT 3 leak?

I now see that pic in the manual and Im not sure that applies to the Bendix type booster.   Our booster doesnt use the filter retainer like the Midland-Ross manual drum brake booster uses....

[Just 6T9 CHGR]

P.S. I don't use DOT 5 either. Our MC's, Calipers, brake cylinders were not designed for it, so unless you have units that are specifically designed/rebuilt for the Silicone DOT-5, AND unless you have totally drained/flushed the existing fluid out, it is a BIG mistake to attempt to change to DOT-5.

This was one of the issues I was afraid about 2 years ago when I was contemplating changing the fluids.....

maybe a call to SSBC & Booster Dewey is in order to get the scoop on the adjustments/fluid info (or at least what they recommend with their brake kits)

[Charger-Bodie]

I really dont know......when I did my SSBC conversion 2 years ago is when I should have switched.....read up on the subject and at the time I got the impression that the DOT 5 was more trouble than it was worth.   The spongy pedal issue concerned me.....

Now I think it might be too late.   can you just drain out all the old DOT 3 and replace it with DOT 5?  Wont all the older seals be damaged from the silicone (rear wheel cylinders, rubber brake hoses)

the dot 5 we get at napa is supossed to bw ok to mix with dot 3 .....

Really?  I've never heard of this type.   All the online articles state that you cannot mix these fluids period.  You must use alchohol to flush the system to clean it enough to make the switch.....

how have you done it?   I hope there is a fluid now that you can mix it a bit.....

Mike, how's the paint holding up on the booster with the DOT 3 leak?

I now see that pic in the manual and Im not sure that applies to the Bendix type booster.   Our booster doesnt use the filter retainer like the Midland-Ross manual drum brake booster uses....

the first one i used it on was my driver 69 valiant 2dr i pulled a blown up 6 banger and put a 318 from a 74 dart k frame disc brakes and all put a 65 b body 8 3/4 and 11x 2 1/2 drums never flushed anything just hooked up the hoses filled the maste {from the dart}with dot 5, bled them out and that thing stoped better than any mopar ive ever owned it was manual disc and 11 x 2 1/2  rear drums

[Mfr426]

Chris, I saw that the diagram was not for our type of booster but if you read further along in the section it once again refers to the measurement of the rod end. The manual is in the garage now but I think the second reference was in the disc brake section. That diagram of of the rod matches my rod (but not necessarily the booster) that I have. The paint on the lower section of my booster is gone now. I wont be pulling it to redo it either since I think I've pulled my brake assembly for the last time (baby #2 due in 9 week so car time is limited).

My entire brake system is brand new. I put in new SS lines, new cailpers, new wheel cylinders, all new pads, new MC, new fluid (duh). I could understand the leaky M/C (even though it was new) but the moisture I doubt.

[resq302]

I did not think that there was an adjustment for the disc brake master cyl cars.  I thought that was only a manual brake master cyl issue?  As for the Dot 3 to Dot 5 change, I stuck with Dot 3 when I redid all my lines and calipers and such only because I have heard that the Dot 5 does not absorb the moisture and will trap pockets of moisture in certain areas causing a scaling of rust issue and having moisture collect in lower areas on the system since silicone will float on water.  The only advantage I have heard of Dot 5 is that it does not ruin the paint but will not displace or absorb moisture like the Dot 3 and remove it from the system.  The key to Dot 3 is to periodically flush or bleed out the system to keep fresh Dot 3 throughout the lines.

[Mfr426]

I just looked at the manual and sure enough there is a comment about checking the rod end measurement on the disc brake booster assembly. There is only one diagram in the manual but the measurement is mentioned at least twice.

I'd like to get the final word on whether or not this rod needs adjustment.

[bill440rt]

Mike & Chris,
If it makes you guys feel any better I'm running DOT 5 in both my '68 & '70 Chargers with no problems. The brake system was completely rebuilt in the '70, stainless sleeved calipers, wheel cylinders, etc. SSBC did the rebuilds years ago, I've been running DOT 5 ever since. I flushed out the system in the '68 when I converted it to DOT 5.
I'll be running DOT 5 as well in the '69 with a completely new SSBC 4-wheel disc brake system.

[Just 6T9 CHGR]

I just got this back from SSBC.....

Chris,
  The calipers in the kit are DOT 5 compatible but I'm not sure about
the master cylinder because that is a part we do not make here. If you
get a seal kit that is compatible with DOT 5 for the master cylinder
then you can use the DOT 5 fluid.


Sincerely,

Bill Cummings
Technical Specialist
Stainless Steel Brakes Corp.
b.cummings@ssbrakes.com
(716)407-0133

Bill, what did you use to "flush out the system"?

[Mfr426]

I hate to ask but what did those SSBC systems cost you guys? Do you like them? With this stroker pushing over 550 HP I think good brakes might be in order...

[Mfr426]

I'm revisiting this issue this week and based on the inexpensive cost of the master cylinder (and the continued comments about replacing it from you folks) I am going to purchase a new one.

Can anyone suggest a good way to drain the fuild from the system, flush the system and refill with clean/new fluid?

Thanks for any comments.

[Just 6T9 CHGR]

Mike, have you sourced one out yet?  I got mine from PartsAmerica.com

[Mfr426]

Hey Chris, this must be the same back end database of parts as it is for Advance Auto Parts. It's the same exact picture of the MC for the disc brake cars that is on Advance. Must be one and the same company?

I'm gong to pick up one this week. I'm debating pulling the booster to paint the entire assembly (which means I'll do it). I'm just not looking forward to crawling under the dash to unbolt those nuts. 

[Just 6T9 CHGR]

I thiink they are all the same parts store (Advance, Chuckers, kragen)   I dont have any of that chain near me so I did it on line