Found a document that describes exactly how a booster works, what is correct behavior and tests to confirm it’s ok or not. Seems I may be needing a new brake booster. Both my booster and my spare don’t seem to hold vacuum.
Doc on troubleshooting brake booster problems
Ranger
#3
Neg. I pretty much never buy OEM parts. Too expensive.
I figured out what the problem was today with my booster that seem go away when I blipped the throttle to heel and toe. The above document was key because it explains how to troubleshoot bad boosters. My new $15 Harbor Freight vacuum gauge helped too. The problem was no o-ring between booster and MC. I installed this MC last Spring when the one that came on New #6 became flakey. But it apparently came w/o it’s o-ring and I didn’t notice during it’s install. So vac was leaking out between the booster and the MC. All is well now. No more getting my ass kicked in the braking zone because I have to start my braking 100’ before everyone else. I will now have power brakes all the way thru the braking zone, vs. having power brakes only briefly.
I had this symptom with two boosters…of course I did, because the o-ring is on the MC.
To figure it out I took my spare booster and taped over it’s big MC hole. Then I connected the booster to the intake via the vac gauge and started the car. The booster that should have leaked, held vacuum. Then I pulled the MC off and noted no o-ring. Just to be sure I taped over the MC hole in the booster that was already in the car and tested it. Sure enough it held vacuum with tape whereas it hadn’t with the MC fastened on an hour prior.
I didn’t have the right o-ring so I made one and used lots of goobage for good measure. When I got it all back together it tested find.
This was a good learning experience. The $200 worth of parts I bought but didn’t need will go into the attic as spares. Any one need a new booster and vac checkvalve?
Ranger
#5
There’s 2 kinds, the cheap 2 port and the expensive 4 port. I have a spare 4 port that I just bought, but now I don’t need. I’ll sell it for $60 shipped which is about $10-$15 cheaper than you’ll find it anywhere else.
The 2 port one is cheap and I don’t have a spare. Using that one requires buying some other parts too tho, like the rubber elbow and a different idle control valve.
jls8177
#6
Thanks Scott. I didn’t realize they were that expensive. I’ll have to get one off of a junkyard car.
Ranger
#7
It’s pretty much impossible to get the checkvalve free of the hoses so you have to take it hoses and all. I busted up a checkvalve trying my goddamndest to get it’s hoses off w/o hurting it.