So a year or two back I went thru my brake system which I thought wasn't working that great. New wheel cylinders in the back, new master cylinder and a thorough bleed of the system. After that the brakes worked awesome. Just like new. So skip ahead to this summer, I'm driving the car and I hit the brakes. Feels like the pedal goes to the floor. The car stops but not great. It wont lock em up, just sort of decelerates to a stop with the pedal pressed all the way down. Now this summer I'm not driving the car a lot for reasons I will touch on later. I drive it a couple of more times and I realize the pedal is not actually going all the way down. Maybe like half to three quarters of the way and stops with normal pressure. I put both feet on the pedal and push hard. The pedal does move a bit more. But like I said you really have to jam it to get to move the rest of the way to the floor. The extra movement does seem to add more pressure to the brakes. This is how it brakes now. So the reason I'm not driving the car much now is that I gave my good carb to JW because he is building me a motor. I have a second junky carb I put on just so I can move the car around (unless you're the Hulk, a 74 Lesabre is not pushable by yourself). Car is hard to start cold and idles like crap. I bring this up because my brake issue started right around the time I swapped carbs. So just looking for thoughts. This is a new one to me.
In my old age my memory is not so good. I want to say it was a reman. Pretty sure I got it from Rock Auto.
Does the car have a vacuum booster? Perhaps that's not working(leaking)? That would require a lot of extra pedal pressure...
Every reman master I've installed has failed within a couple years. Check for a leak between the master and booster. I'd bet a beer you'll find brake fluid leaking out the back of it.
Well I took a look and there was no leak that I could see. Popped the lid off and the master was full (doing that did spill some fluid onto the booster. But i checked for leaks before i opened the master).
You can also test the check valve. Get a clean piece of hose and pop the hose off the check valve where it runs into the booster. Put the clean hose on there and then try sucking (should work) and blowing (shouldn't work) If you can blow into it. the check valve is bad and the booster is leaking back.
I have a shelf in the garage filled with rebuilt masters and another shelf filled with adjustable fuel pressure regulators. While the regulators were a crap shoot outta the box, the reman masters were all crap right outta the box, had to buy new in box....Jim
Well I might be missing something but it seems like the carb is leaking a ton from somewhere so the vacuum is super low. That would explain the really poor idle and a lack of vacuum for the brake booster. No vacuum, no power brakes... this all started when you swapped the carb... I've been wrong plenty of times, but it sure seems logical...
My personal preference when it comes to brakes is always new never remanufactured. Nobody likes surprises when they step in the brakes.
Put a vacuum guage on it.... Let us know what it is at idle. Use WD40 or equivalent to look for Vacuum leaks around/ under carb if it is indeed low...JIM
Stupid phone lost what I wrote so here it is again. So I checked the check valve and its OK. I put a vacuum gauge on one of the lowest connections on the carb (where the air cleaner has a connection). After the car warmed up, the vacuum bounced between 6 and 9 in hg. I did spray lots of joints with starter fluid. No changes in idle noted. Finally I looked up my purchase record at rock auto. It was a new master from AC Delco.
6-9 is not enough vacuum. You probably have it hooked to the wrong port. Need at least 14 at a minmum.
It's a junk carb but I'm willing to retest with a different port. At this point I'm starting to lean towards it's a carb issue that's hurting the vacuum.
with a mild cam, if the gauge is bouncing you do have some issue somewhere. I found this interesting and informative https://www.moroso.com/pub/media/wysiwyg/PDFs/hotrod-vacuum-gauge.pdf
Tom is correct...not enough vacuum. If this is a temp carb to move it around a bit, I would not chase the cause of it, unless you are curious or need to drive it elsewhere... Not sure where you are located? Up north, car driving season is about up. Sounds like you'll be getting a fresh engine soon.
Thanks guys for helping me to narrow it down to the carb. I won't be trying to fix the carb but it's good to know it's not a real brake issue.
