ddahlgren

To sum up tires Kumo's all weather high performance though fairly inexpensive grippy enough for me until I get some body roll under control. I can easily chirp them when the trans shifts to second and a bit spirited driving less than 2 years old. The brake pedal is hard and hardly different at all engine running or not. Installed Hawk HPS pads new GM rotors J55 fronts bias springs flushed system. On a dry road at 60 mph if I slam the brakes on they will not so much as squeak a tire or set off abs. I talked to an independant rebuild for the booster and he assured me my Corvette power brakes should act like any other GM power brake like the ones in my 2002 Pontiac with a v6 that will probably outstop the Corvette currently with small single piston calipers and they are much different between the engine running and stopped. The booster is off to the rebuilder and will let everyone know how it all works out when i get it back and installed.
Dave

anciano

I guess that makes the Corvette engineers even more idiotic than me, because they put the ABS feature into cars that don't need it. What were they thinking?

Or maybe "hard as rock pieces of crap" were the specs they supplied when ordering from the OEM supplier.

RedLS1GTO

Or it could be that ABS was designed more for less than optimal road conditions... just a thought.

I have averaged almost 20,000 miles a year in ABS equipped Corvettes on street tires over the last decade and can count on 1 hand the times I have had them into ABS on a dry road.

Out of curiosity, what kind of tires (how old and how many miles) are on your super duper brake equipped Corvette that goes around constantly bouncing off of ABS?

anciano

Not that this dialogue is worth continuing, since you seem convinced that your non-functional ABS is the norm, but I have newish (500 miles or so) Falken tires. They are not the stickiest but have an A traction rating.

But there's no need for us to debate this issue. Ask any Chevrolet dealer or brake specialist if your car should be able to lock up your brakes and/or activate the ABS. If they say yes, then you can share your "expert" opinion with them and set them straight. Poor dears.

BTW, I have not had to use the ABS in normal driving -- I've just made sure a few times that it is there if ever needed. The fact that you somehow concluded that I am "constantly bouncing off ABS" indicates that you either have a problem with reading comprehension or (more likely) make up your own reality as you go along.

If you are happy with your braking, good for you. It's all the same to me if your car has no brakes at all. Just don't follow me too close, OK?

Over and out. Really.

RedLS1GTO

First off genius... if you are going to insult me, the plural of deer is... deer (not dears). That was an awesome insult by the way. I'm guessing that you are exactly the type that if you had a deer in front of you on the highway you would panic, plant the brake pedal through the floor at 70 mph, and cause a 10 car wreck.

Second... I wouldn't put Falken tires on an Escort, much less a Corvette. If you were paying attention, I said long ago that my 87 would lock up the factory wheels and tires so yes, I am certain that you can lock those things up and get into ABS with no problem at all. Try putting on a set of C5 Z06 sized wheels (which is not uncommon for C4s) with a good set of tires, like Michelin PS2s and watch the difference. It may come as a surprise to you but locking up the tires isn't the point of braking. There is a whole lot of money spent and research done to tune suspensions so that the brakes don't lock up.

Third... If your idea of an expert is a Chevrolet dealer, you really are an idiot.

Fourth... As for my non functional ABS, want to bet on whose car stops in a shorter distance? I'll even let you choose which one of the non-functional cars I use. You say that you test your ABS occasionally to make sure it works... I test the brake systems that I have built at 160mph with a wall in front of me but hey, you're right, I probably have absolutely no idea what I am talking about. What do you say we stop from 30, 60, 90, and 150 back to back? I think we should have a pretty clear winner by then.

All of this started because you said that a properly functioning system should ALWAYS be able to lock up the brakes on a smooth dry road. You were wrong then and you still are. In the case of the C4, the brakes (especially the non J55) simply don't have the stopping power to lock up big sticky tires even when in 100% working order. If I took my track wheels and tires and bolted them on your car without any other changes (we'll use yours since in your "expert" opinion, the ABS on all of my Corvettes is broken) do you really think that you would be able to lock them up on smooth dry pavement? I'll give you a hint... the answer is no.

ddahlgren

Got some info from the booster rebuilder and mentioned the first one he saw with the pedal rod + 0.250 so not imagining anything this was Thursday last week so should have it middle of next week to install and test. They did find issues and suggested I do not neeed to look for another solution sounds promising!!!
Dave

jhammons01

There is an ABS reset procedure.

I am shocked that this thread went on so long..................I always chime in on these threads and the ABS reset always works....YOUR ABS is functioning correctly.....it just needs it's computer reset.

Alas....I don't know how to reset the ABS module....but other do. So slam me for knowing the answer....I can diagnose your cancer...I just don't know how to treat it.

Search for ABS reset and see what you get.

Before you scoff, I have received three PMs in the past telling me thanks for pointing out a simple fix....all from folks that replaced their entire brake system trying to address the hard brake pedal syndrome.

tequilaboy

Just a word of caution:

If you adjust the output pushrod rod length for correct clearance by partially appling the booster first (so that it is easier to hold the pushrod stationary with vice grips or pliers while turning the adjustment screw):

Be sure to keep pressure on the input rod while doing so, since the return spring has sufficient force to separate the output rod from the control group within the booster. Ask me how I know.

For fun, I just took my old booster core apart. It was very easy to disassemble. I removed the two studs first and then applied heat with a heat gun around the circumferential joint.

After a couple of times around the booster shell with the heat gun, the shell halves popped apart due to the return spring force. I saw it start to move just before it popped. Keeping the nuts loosely on the studs wouldn't be a bad idea to keep parts from flying when the shell comes apart.

I'll post up some pictures of the internal components when I get a chance. Should be an easy booster to rebuild if you can get the internal parts.

Update: There's only a small spring washer with 6 little radial tabs that prevents the output rod from being pulled out of its bore. Looking at the parts, its easy to see how it failed as I adjusted the output pushrod for length.

The spring washer doesn't prevent the rod from fitting back where it belongs, so I just put it back into position and installed it. The output rod would need to travel outward approx 10 mm independently of the control group to ever fall out of position in service. With the master cylinder in place, this should never happen, since the master cylinder should return faster than the booster. I'm still using the new (damaged) booster, since it works fine.

Note: My original booster failed due to a tear in the diaphram. No surprises there.

klkordzi

You mentioned in your original post that you replaced the calipers. When you installed them, did you install them with the bleeders facing up?

jhammons01

ABS module.....reset.......leave the wrenches in the box

ddahlgren

Yes bleeders up and flushed fluid with DOT 3 new Hawk HPS pads new rotors from Corvette recyling rebuilt master stainless brake lines and drm spring. Brakes better pedal still hard. The rebuilder said the booster had issues with the control valve and knew I did not care if it was a broken booster but just wanted to rule it out of possibilities. He seems like a straight shooter with no reason to lie to me. I will certainly bring the car to the dealer if after reinstalling the booster there is still a problem. Without the power assist feel the booster to me is the only answer I can see no connection from the ABS to the fact the pedal has no power assist. Sure I can have power assist and poor braking and that would send me in another direction

tequilaboy

Here are some booster pics:

jhammons01

http://forums.corvetteforum.com/c4-t...d-0-spent.html
http://forums.corvetteforum.com/c4-t...n-finally.html
http://forums.corvetteforum.com/c4-t...-problems.html

The third link has a step by step how to reset the ABS module and clear the codes. Once the codes are clear, the ABS module senses correctly again.......just sayin'

jhammons01

Here's another one

http://forums.corvetteforum.com/1572226709-post19.html

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

red 90

I went to a car show today at the IX center in cleveland and the corvette club was there and I asked for a c4 guru and they laughed. What ya got they said ?. I hava a 90 and the service abs light comes on after about 30 to 40 seconds after start, hard pedal all of the time but dosent want to stop well, they said booster is bad,.. what do you think??

ddahlgren

Got the booster on this weekend took the car for a ride this morning and all seems like a normal car now with about 1 inch of softer pedal pressure before getting to a harder pedal. Have not bothered with a panic stop yet but does require about half the effort to get previous braking results. So maybe it is not always the abs... I would reccomend anyone with a 9 or 91 to get your booster rebuilt as all the rebuilders lump them in with 89 and back and it is not the same part.
Dave

jhammons01

wait till you actually reset the ABS module

TomP.

I used the third write up most common abs problems to reset the ABS in My 1990 Vette . I connected pin A to G turned on the ignition and followed the procedure . I never saw a display but when I hit ENG/MET i heard a clicking noise . When I drove the car the brakes are really working great now . Plus when I start it up that ABS test sounds like relays clicking . Before when I started I heard what I though was a caliper dragging or a brake pad rubbing a disc .