: Weird brake problem
02-25-2005, 05:05 AM
Here's one for you:
Installed a 455 buick in my 76 Elky. Long duration cam, lopey idle but not too bad.
Problem is , when it's in drive brakes work as advertised.
Throw it in reverse and the brake pedal is very hard to push and takes forever to engage.
How do the brakes know what gear I'm in !?
Any ideas ?
02-25-2005, 10:46 AM
First thing I would do is hook up a vacumn guage and see if the vacumn available to the booster is different in R and D.
02-25-2005, 12:21 PM
Vacum modulator problem at trans, causing engine vacum to dump when reverse is selected. Just a guess.
02-26-2005, 10:39 PM
For some reason I cannot explain, you will experience this problem in reverse IF your vacuum source is marginal to inadequate. My 86 has a vacuum reservoir (vacuum ball about half the size of a volley ball) installed all the way to the front, driver side, inside fender well, just above the steering assembly. It collapsed, from age I think, and caused the brakes in reverse to work just like yours does. I replaced the collapsed vacuum reservoir and the problem went right away.
By the way, in this condition, you will sometimes experience a hard brake pedal in drive but nothing like in reverse. Why? It beats me, but it is a fact. If you learn why this is , let me know.
02-27-2005, 03:25 PM
???? Sounds like an aftermarket vacumn reservoir could handle the problem.
03-01-2005, 04:56 AM
I have a couple of vacuum reservoirs lying around , I'll hook one up and see if it helps.
Thanks for the help.
03-01-2005, 06:07 AM
That's a good one, Let us know.
03-05-2005, 10:05 PM
Installed a vacuum reservoir inline with the vacuum modulator on the trans and made the tranny freak out!
Shift points were ungodly high ( 6000rpm! )
Scared the hell out of me...
Looks like I'll need to plumb them into the brake vacuum line. Then hopefully it will help the brake booster when the pedals depressed.
03-06-2005, 06:26 AM
El Kujo, I don't think the resevoir is supposed to be inline with the vacuum modulator. It's supposed to have engine vacuum to it but not a constant supply of it. I think that would cause the shift points to be too high.
03-06-2005, 04:15 PM
Yeah , I kinda figured that out after my tach went to 6 grand!
Amazingly nothing blew up.
I'll try plumbing it into the brake booster and see if that helps..
Chalk it up to experimentation.
At least it didn't cost anything..(this time)
03-09-2005, 05:28 PM
installed in your vacuum line to the resivior should be a vacuum check valve. if its not there you could also experience this, or if you pump the pedal a couple times. your moraine booster is a resivior. if the check valve can be blown through either way replace it and you should be fine. inline to the resivior if it is pulling about 14" vacuum, it should work reliably, unless the check valve is bad. they only cost a couple bucks at the part stores in the help section usually.
03-09-2005, 05:31 PM
typo-sorry-you should be able to blow through it one way only, the direction suction towards the intake. vaccum generated by intake, you follow?
03-09-2005, 10:27 PM
A faulty check valve in the booster will make you crazy. I have seen dishonest mechanics remove the booster, clean and paint it, then reinstall it with a new $3.00 check valve and charge the customer $150.00 for a rebuilt booster. And people wonder why auto mechanics have a bad reputation.
03-09-2005, 10:30 PM
Just remembered. I once found a small crack in the vacuum line at the check valve and it caused a hard petal at times. To test it, I taped it up with electrical tape and the problem went away. Went to the parts store, bought new hose and intalled for a permanent fix.
03-10-2005, 05:06 AM
Thanks for all the tips. I'll get me a vacuum gauge and check all of those things this weekend.
While scratching my head over this the other day I remembered that a few years back I replaced the booster with one from a junkyard, ( I was VERY broke at the time).
An internal leak would probably cause the same symptoms.