Herb

I jumped in my 93 C4 and to my surprise I could hardly come to a stop.

I had to press very hard to get it to slow to a stop.

Is this a booster problem?
Thanks
Herb

runner140*

Usually, hard pedel= booster problem
soft pedel = master cylinder problem
Do you hear a hissing when you depress the brake pedel?

383vett

New booster is in order.

jhammons01

For a '93, and if it happened over night......there is a ABS computer reset technique that I would look at primarily.

I don't know how to do it as I have an '84....but there are many threads on the topic.

ABS Codes....or something like that.

bowtie350_428

I have the same problem, so I am just curious. But how would this be related to ABS?

jhammons01

^^You've tapped me as far as info is concerned. I "think" the ABS computer is fighting against your foot.....it is misaligned. Once you reset the ABS computer it makes the pedal feel normal again.

I can't speak from experience....only what I've read here.

jwt1603

little98dime

After looking over the brake system from my 85 I noticed it is exactly the same as my 98 s10. I had the brake booster go out on my truck and it had the same symptoms as what you are having. A brake booster would more than likely solve your problem.

Analog Kid

OP,
I also have a similar thing and it has been on my "to fix list" for 2 months now, a list that keeps getting longer for some reason.
Anyways, your post got me started on this so I did a search (there is a ton of stuff on it) and it seems that you clear the ABS codes via the LCD screen and fuel info buttons and then activate the ABS while driving a few times by getting on the brakes hard and that worked for a few folks.
I did all of that tonight and long story short, it did nothing for me. Brakes still take much more effort than a sports car should to bring to a stop.
So give it a shot, it's free to try after all, but maybe it really is a bad booster or check valve.

If you want to clear your codes, give me a PM and I'll talk you through the paperclip method via phone or something as it is kind of long to explain here.

steve40th

Booster is definitely the problem. Also, do you have headers?

92ZR1WANNABE

Had the same exact thing happen in my 92. Booster it was.

pcolt94

If you have a high hard pedal which is radically different than the day before, chances are it is the booster.

As far as resetting the ABS system, some say it has helped and some say it does not. It all depends if there are codes stored in module 9. It also said that locking the brakes up on gravel will cycle the ABS pump and increase braking power. Never the less when any of these things are done the brake pressure modulator valve in pump near the EBTCM clicks and resets. If you go into module 9.7 to reset it regardless of any codes, you can hear the valves.

Truth or fiction sometimes it may work depending if there is a problem to begin with that can be rectified. But this will not make the pedal feel like a bad booster but will increase braking power and the pedal will feel about the same.

l98tpi

JrRifleCoach

If the booster is bad, vacuum restricted, or the push rod between the MC and the booster is not of the correct length,
a hard pedal can result.

But we have also seen where the ABS system is behaving poorly and this will also cause for a hard pedal.

Some CF'rs have had the ABS "reset" which has cured the problem.
I have no idea what is required to reset this device .

So if anyone knows where/how to do this, now is a good time to chime in.

pcolt94

I will say it again for all who did not actually see it in my above post in case it was not clear.

To reset the ABS, go into the diagnostic mode and using the manual buttons enter module 9 and go to sub module 9.7 and clear the brake codes and reset the system. Taking the battery cable off is not a short cut that will work to simulate this process.

jhammons01

Thanks Colt and Thanks Jr Rifle Coach. My point earlier was that this ABS module has had some replace Boosters, Brake shoes, Rotors, etc. and the whole time it was the ABS messing them up.

I just feel that resetting the ABS module should be one of the items listed as a fix for "Hard brake pedal"

I mean really, wouldn't you rather find out that it was a "Reset" process FIRST rather than after you payed for and installed a Booster??

I would.....

neat

Are you sure the vacuum line didn't come unhooked from the booster?

littlesk8cracker

if you do end up having to replace the booster, checkout the step by step guide i did about a month ago complete with pictures on how to change it out. pedal was getting hard on my 94, so i changed it out and problem solved

pcolt94

To clear PCM/ECM codes do the following:

Short A and B on the connector. (On the 92-93)

To clear ABS/ASR codes do the following

You’re looking for “9.7” on the trip odo

1. Press the trip reset button on the DIC until the desired system is displayed. In this case it will be 9.0.

2. Press trip/odo button on the DIC until the desired diagnostic mode(9.7) is displayed on the trip monitor area of the cluster.

3. Press & hold the eng/met button on the DIC until "---" is
displayed in the speedometer area of the cluster, this will clear PCM codes.

This should work

JrRifleCoach

Hey! pcolt94!!
Thats great!
Exactly what I had hoped someone would post.
Maybe the newb is still following this thread......

Except the earlier C4's are handicapped with the old ECM.

These need a special diagnostic box found at Chevy dealerships.

Maybe someone has access to one of these as well?????