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Hello all, I seem to be having a hard time figuring out what my problem is. Hopefully I can narrow it down for some of you.
The other day on my 1989 corvette the brakes decided to get really hard and I knew immediately it was the brake booster. The booster arrived today and I got it installed and have noticed a few things. It seems as if the new booster is actually smaller around than the old while also having a longer rod that goes to the brake pedal from the booster, I found this out by the new pedal height compared to the old (about an inch higher or so). The brakes work fantastic, way better than before, but I am having issues with the pedal.
The pedal at its new point with the car off and pressing it a few times to get rid of the vacuum will stay firmly seated at the top against the stop like it should and I adjust the cruise and brake switches accordingly. With the car on and running however, the pedal likes to drop I'd say maybe half an inch below this point and has a decent amount of free play. When I noticed this, I adjusted the switches so my brake lights were not on all the time and it takes the slack out of the pedal somewhat.
Before my pedal was just slightly higher than my gas pedal and now it is a lot higher causing my foot to bump it a little letting off the gas to brake and it pops the cruise and brake light switch towards the rear of the car and brings back the slack. Also if I let off the brakes fast and it bounces back it moves the switches too.
I was wondering if maybe the booster is not functioning 100% or what but it is annoying. Any help or guidance would be awesome. If you need anymore info let me know, but I think I covered it all haha.
Reseller, brand and part# of the booster you used might help to maybe ID a specific trend to expect maybe for future needs. Someone might also recognize the brand and part# and recall what they experienced. Since it's installed you can't compare the push rod lengths but what is the diameter of the new chamber? Any other issues when installing?
Having just done it you haven't had a chance to call the reseller or maybe the tech support of the manufacturer but it might be the first thing to do.
It is the steel brake booster from Zip Corvette. The rod on the new one is a little bit longer, but barely as I just checked. The new one is over a different design or something as my old one has a metal square plate on the back that the new one does not have which I believe might be the reason for the longer rod on the new one. Other than that everything else is the exact same.
It is acting like the return spring inside is not pushing the rod all the way back out or something similar. I have some videos but am not 100% sure how to post them without using youtube.
I have adjusted the brake and cruise switch to multiple position and no matter what, when I press the brakes and then release with the car running the pedal will not go back up the last quarter of an inch or so. Plus my switches are stripped a little for some reason but I can zip tie them in place haha.
It is driveable, but I have to pull of on the brake pedal to get it up the last little bit so the lights go out and so I can use my cruise and that is when I thought just adjust the switches, but no matter the position the pedal will not go up that last little bit.
I believe the next move before attempting anything unusual is to call ZIP. I've always thought them to be pretty good guys and seem better with the TECH SUPPORT than some. I'd think you couldn't be the first and maybe it's a potential packaging issue that they're familiar with. How closely did you compare before the install? If you can supply them with snapshots of yours to compare to maybe another unit in their stock it would help. Are you quite sure yours that you removed was original?
Thank you, I will call them the first chance I get. I have another one coming in tomorrow from them that I originally order, needed one sooner than expected, and will also compare the 2 and maybe swap them just to see.
the longer rod is not letting the internal valve seal and is keeping atmospheric pressure on the back of the diaphragm. you need to either get a shorter rod or adjust the linkage until the pedal has about 1/4 inch of play before it starts to compress the booster valve.
Here are some images of the new one that arrived compared to the old one. You can see the rod length is a good half and inch or more than the old one.
I also noticed this backing plate on the old one, the sqaure silver piece, and took it off and put it on the new one. It helped a little bit, but did not fix the problem of the pedal going all the way back to the top.
EDIT: The brake booster show is a new one that came in and is not the same as the one in the car. Only difference though is the yellow check valve. I will try tomorrow to swap the newly received one in and see if that helps any.
Last edited by Red89'-L98; 01-05-2017 at 07:04 PM.
First I show that the brake pedal when released slowly will not come up all the way unless moved by hand to the top and then once let go, it goes down just a tiny bit. I also noticed when down there and filmed it, that pressing the throttle is allowing the brake pedal to drop slightly to the same spot that as if I were to slowly release it
Last edited by Red89'-L98; 01-05-2017 at 07:08 PM.
I had a situation with my booster about a year ago when I replaced it which was under warranty from AutoZone. The new booster came with a shorter rod and skinner. After 2 weeks and 5 boosters that I ordered or saw at other AZ stores I finally get the correct one.
The problem was Cardone was manufacturing the booster wrong installing the wrong rod. All boxes had the correct part number. The pedal was too close to the floor and the switches did not contact. I ended up even talking to the factory and explained the problem and spend much time on this till I got everything straighten out and was really a major pain.
The skinner rod looked like it fit the earlier years of the C4. I have a 94.
Line: BHH | Part # 54-71401
$152.99 Each
Plus Core $20.00
Same for yours
I don't remember any spring return or anything but if you adjust the rod in or out will it not take out play in the backside. Just a thought. Vid not working
12-30-2016, 01:25 AM
Brake pedal problems
