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sticking brake booster

Posted: November 15, 2015, 2:30 pm
by sproino
It came to me seized. I squirted silicone in there, and it got it free, to a point. I had it to where it would spring back slowly, over about ten seconds or so. Then it sat for a day or two and now it's stuck in the down position again.

It's my 66 F-350. Am I going to have to pay through the nose to get this thing rebuilt?

Re: sticking brake booster

Posted: November 16, 2015, 11:59 am
by sproino
Here's a pickle.

It isn't stuck; the brake booster is too strong. It's applying the brakes all by itself.

Re: sticking brake booster

Posted: November 16, 2015, 4:00 pm
by Toyz
Need to set your brake pedal linkage to correct dimension and/ or adjust the output rod on the booster.

Re: sticking brake booster

Posted: November 16, 2015, 8:02 pm
by Mr. Jones
Sporino,
Two questions
Is the booster mounted and connected to vacuum?
Are your brakes totally locked up?
If they're locked up try this. Chock your wheels,start engine and open one of the bleeder valves.If that frees up the system then as Toyz mentioned the booster push rod is to long.can text shop manual specs for proper length,pm a number if interested
Dan

Re: sticking brake booster

Posted: November 16, 2015, 10:11 pm
by Toyz
OK, time to think this thru! Is your booster firewall mounted? If so, does it have a band separating the two shell halves? Since you mentioned the booster being seized before; if in fact it is the Midland booster, I would suspect the control assembly has sticking parts even if the diaphragm itself seems to be fully retracting. Replacing the Miidland booster usually does not require any external adjustments, so I do not believe that to be the problem from the limited info. Remove the vacuum source and see if that has any effect. I suspect it will not, which still leaves the possibility of problems in the master cylinder as well as booster. That unit used to be serviced as an assembly, master and booster; I am not sure if it is that way in the aftermarket, or even still available.
Paul