Master cylinder rod adjustment needed after hooking up vacuum line?

[Dirtyrat]

Tonight I got the motor running again, and it seems with the vac line hooked up to be brake booster, the pedal feels like it has 2" of travel before resistance?

When I bled the brakes with no vac source it was a nice firm pedal [S[S[S

Any thoughts or lessons learned from you all would be excellent right about now...

 

[Yankee Transplant]

wow .. but does it stop real good ? or is the pedal almost to the floor ?

 

[Dirtyrat]

wow .. but does it stop real good ? or is the pedal almost to the floor ?

I have not driven it, I was going to see if it at least still stops the wheel from spinning... its weird... I've never seen anything like that with the brakes becoming like a sponge when vac is applied to the booster. Especially since I had a rock solid pedal prior...

 

[Yankee Transplant]

if it stops like a champ .... maybe adjust the rod a tad to give you a higher pedal Just a thought [S

 

[Dirtyrat]

if it stops like a champ .... maybe adjust the rod a tad to give you a higher pedal Just a thought [S

I'll try it once I get it back on the ground, but I'd like to hear from other people as well if they have seen anything like it?[S[S

 

[Yankee Transplant]

you got that right Im not good with brakes [S got to be careful on the adjusting so it dont drag I just put some brakes on a yota and they were like that not running good pedal when running a little lower pedal but it stops on a dime ..

 

[Bamamav]

Funny, but that's the way mine on the Lincoln act. Without vacuum, pedal was very solid, after I hooked up the vacuum, pedal goes down a couple of inches before it "hooks", but it still has plenty of pedal and stops fine. I almost left the vacuum off of mine after that first time, but I adjusted to it.

 

[rustybeercan]

Had the same type problem, turned out the booster had a vacuum leak! [S

Beercan

 

[I-R-POPS]

Hey DR, I had the same thing on my Dodge and adjusted the rear drums up and it helped a bunch. Don't know if that's your case but it might be worth checking.

Sounds like you're getting close. Don't weaken and remember,you can sleep when you're dead.

 

[Dirtyrat]

Another person mentioned bleeding them as they had seen a good pedal with no vacuum, and spongy with vac applied...

The other weird thing is with the motor off, when I hit the pedal I can hear sound through the vac line into the intake plenum, kinda sounds like a duck... I know there are no blockages because its brand new line and it did it when there was no vac line... I'm really hoping its not a bad booster...

Hopefully I can bleed them tomorrow or later today and if I cant get it to improve, I'll be calling MP Brakes to see about a replacement booster I guess...

Is there any way to test the booster for leaks?

 

[Neverdone]

Old school check for vac leak? Spray with WD40 when running and listen for motor rpm change..... If leaking idle up???

 

[Yankee Transplant]

On a quiet car you can push the brake and hear air leak or vacuum suck the whole time you have you foot on the pedale.

 

[Dirtyrat]

I talked to MP Brakes today, they suggested looking at the rod between the booster and the MC and make sure that is correctly adjusted.

(I did re-bleed the brakes last night, but no real pedal feel with vac applied. it does stop the wheels, and seems like its capable of stopping but feels like stepping on an egg never really feels firm on the pedal or any pedal feedback...)

I'll post what I find tonight as soon as I can, maybe it can help someone else at some point.

 

[christcrusader13]

I'd like to know what you find, I have had this issue on my 64 Chevy C-10 pick-up 'Vicky' for some time. I thought I didn't have enough brake pressure, so I adjusted the rod and it stopped quicker, but now it's doing the same thing, all new brakes, new brake lines, and bled with an air bleeder, so I'm thinking it may be the booster is leaking somewhere, I'm going to test the brakes without the booster now, to see if it makes a difference.

 

[Dirtyrat]

My booster had no adjustable rod, but I did pull the MC off and look at it without removing the lines, and I adjusted the pedal rod some more, and it appears to be working as designed. I have not tested it with vacuum applied yet, I am going to bleed them one more time tonight and hopefully a test drive to make sure it works even with the weirdish pedal feel.

MP Brakes reminded me that if the booster was leaking it would be an excessively hard pedal, not what I have now. And this is the largest bore MC they make, so fluid travel is not an issue... however the safety setup for the brake light I needed to remove and put the steel plug in to help bleed too, which I will be bleeding them that way this evening to make sure I have all the air out of the system.

 

[Yankee Transplant]

Maybe you will get lucky and just that little adjustment was all you needed

 

[Dirtyrat]

So far nothing corrected the issue, I disconnected the booster vac line, and plugged the intake port for now. Firm pedal, but it stopped fine.

I'm going to be getting a new booster from MP Brakes hopefully sooner than later to test out.