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I have this issue with my truck 1976 4X4 Ranger break pedal not returning all the way up when the truck is not running the pedal is hard and the pedal comes back up normal but as soon as I start the truck and the break booster works the pedal gets softer and breaks good but doesn’t return all the way
new master cylinder and booster along with breaks bleeding work done
any ideas
maybe the vacuum is not enough to bring the pedal back all the way or need to re bleed the breaks but the feel great when the truck is off
any help would be much appreciated
thanks
Vacuum does not pull the pedal up. A return spring in the master cylinder pushes the piston back towards the booster, that in turn pushes the brake pedal up. If anything, vacuum might pull the pedal down some if there is an issue inside the booster. You say brakes are good .... so maybe add a spring to pull up on the pedal, under the dash.
When you step on the brake pedal with engine running, a valve is moved in the booster that lets the vacuum if present pull a diaphragm to help you apply more pressure. Might look at some videos.
Yes the new booster and MC are brand new from AutoZone and seems that they work properly when the truck is off the pedal feels hard and breaks with no power breaks of course
but as soon as I fire up the truck the pedal works but doesn’t return to the non break position all the way causing the truck to have undesirable breaking
I can try to adjust the rod in the master cylinder more if that helps
I guess the smaller I make the rod the higher the pedal will go right ?
also someone said sometimes even when the are not leaking the wheels cylinders can suck air and cause a pedal act weird
but since my pedal breaks fine just doesn’t return all the way I might just go for a spring adapted to bring it all the way up every time
If you mess with that adjustment and mess up, you'll either be pumping the pedal, or the brakes will maybe never release.
I bought a simple gauge to measure mine.
... since my pedal breaks fine just doesn’t return all the way I might just go for a spring adapted to bring it all the way up every time
That would be just masking the defect, even if it worked. Say if the return problem is in the MC itself, the piston will still be extended.
I think there was a similar problem posted not long ago and it was found to be a defective booster. You have to be careful of where you buys parts now.
