Todd B

I've searched the forum and checked the shop manual. But still can't find an answer to the following quesiton. I have a 96 C2 with ABS/ADB, so it's the 4 circuit ABS. While at the MetroNY DE at Summit Point, I was able to lock the wheels during heavy braking. This was from various speeds, and either one wheel or multiple would lock up. I have no ABS/ADB lights light on the dash. I only felt a slight pluse in the brake pedal, it's very faint. So my question, Is this normal? Or should I go and find somebody with a Hammer to read the codes from the ABS controller. Could the ABS pump have air in it and the system thinks it's operating fine?

Thanks in advance for any insight.

Todd

tom_993

Not normal. You should not be able to lock up your wheels at all. Don't know what the problem could be. I'd certainly have it checked out.

Tom
'95 993

Todd B

Thanks Tom. I'm going to take the car in next week to get things checked out.

Todd

Mark in Baltimore

Todd- Saaaay, I know that car behind you! Did Lisa shoot that? Your car looks great; nice shot.

Where at Summit was your car locking up? Was it Turn 5?

I thoroughly enjoyed running with you Todd. Summit is quite challenging. What's your next DE?

Todd B

I was getting some wheel lock in turns 1, 5 & 6 at various times depending on how hard I was breaking. Turn 5 tends to lock up the front left wheel more often, but it depends on my position on the track. May have something to do with the slope of the track. I don't feel the pedal pulse before the wheels start to lock, and I'm applying steady pressure.

Yea it was fun running together, it's always nice to have somebody with a similar car. I was bummed when I saw you moved up out of the run group. All I was left to play with was a 930, I could not stay with him on the straights.

My next DE is the Potomac time trails weekend later this month.

Lisa did get the picture, she's getting better with the digital camera. Here's the orginal.

Todd



And here's one I took later on Sunday. Looks like you are getting on the brakes before turn 10.

Greg H.

Todd -

Having just driven a 930 yesterday, I can imagine that he would pull you on the straights. Could you catch him on the turns or was the car clearly faster around the track? I drove a friend's 1976 Turbo Carrera, which I understand has the least power of all the Turbos, and it was quicker'n heck from 4000 to 6000 RPM. But the handling was less than confidence inspiring. My friend drove my 993 and when he got out his comments were 1) Nice brakes. 2) That car is glued to the road. And I have stock suspension.

Greg

Todd B

Greg,

First he was behind me and I would loose him through the twisty's (turns 6, 7, 8, 9), but he would catch up by the end of the straight. I let him pass then tried to stay with him, only to fall back on the straight. I would slowly catch up again in the twisty's, but could never quite get on his tail. It was interesting to see that when he lifted his tailpipe shot flames.

Todd

Kim thanks for the input. I'm taking it in on Monday.

B-Line

Hey Todd,

My last time at Sebring I was chasing a 930 RUF. He was shooting flames too. I was much faster than he was but he wouldn't point me by. He definately had the horsepower but not the suspension..
Here's the link to the video.
Enjoy!

B

http://www.burnpro.com/videos/Winter..._002%20_LO.zip

p.s. if any of you guys from "Hey Wait For Me Racing" read this..
SORRY.. I'll try to slow down :+)

Sam N

Todd,

My brakes were also locking (front left) into 5 in the Chute @ Summit. I think that with the uneven/bumpy suspension, loading bias towards the front of the car and the high speed, the ABS is unable to modulate fast enough.

It happened several times too.

Btw, any pics of me?

Sam

Edward

Todd,

Just guessing here, but is it possible that the wheels aren't really "locking" as much as they are just chirping under heavy braking on uneven/rippled surfaces. What Sam says makes sense, especially if you're running street tires since these would be more likely to chirp under "extenuating" circumstances than R rubber. The slight pulse you say you feel is consistent to what I've experienced, so perhaps it's just the ABS trying to keep up with an uncooperative road surface.
A simple test would be just driving down an empty street or lot at 30 or so, find smooth, even pavement, then STAND on the brakes. They either will lock or not.

Edward

Todd B

Sam,
Thanks for the input. That's the same thing I have experienced. My instructos always freak when they hear the wheels chirp there, the question that's always asked "doesn't this car have ABS?"

I did have what seemed to be 4 wheel lock going into turn one. I ended up modulating the brakes and each time I went beyond the threshold the wheels locked.

Sorry I didn't get any pictures of you, couldn't get any since we were in the same run group. But I think I did get some video of you during the third session on tuesday, before my camera's battery gave out. I haven't had time to watch it or pull it into my system. I'll let you know if I have something.

Edward,

I dug through the shop manuals last night and figured that I would reseat all of the connections in the trunk. Plus swap the two relays just to see if there's anything different. After reseating all of the connections, I took the car for a drive. Got up to speed and went hard on the brakes. I tried this before resetting the connections and I had wheel lock. Now I get the front left wheel in a locking and rolling cycle (leaving a black dotted line on the road), the front right is in full lock (leaving a long black line). I kept steady pressure on the pedal during the breaking. One thing I did find in the shop manual is a faulty solenoid will not throw a fault code or light the dash light. So this might be my issue or a cable/harness problem.

I have Michelin Pilot Sport Cups for tires

Todd

Edward

Todd,

Interesting find, thanks for the update. I 'd be interested in learning what your final fix is. Perhaps you can post when you get it all resolved. Thanks!

Edward

Todd B

Here's an update on my ABS problem.
In short, I was able to fix my problem . Ended up being a bad ABS brain.

The long version: I didn't take the car in to read the codes off of the ABS brain, since the service manager said if there's no fault light then there's no codes. So I went through all of the procedures in the diagnostic volume of shop manual. I was able to manually fire all of the solenoids and run the pump. All the cables from the brain connector so the pump showed the right resistance, so there were no shorts or broken connections. Both relays also checked out. Since it seemed that the solenoids where firing, at least one wheel was pulsing. I had narrowed my search to the pump. I ended up wiring a light bulb to the pump relay to see if it would light, (I didn't think the wife would ride in the trunk and tell me if the pump was coming on or not ). The light never came on under heavy breaking. So I now knew I had it narrowed down to the ABS brain. I bought a new one and replaced it last night. All is happy now. And I'm very happy I did not have to replace the pump.

Todd

Edward

Excellent job troubleshooting, Todd! Thanks!. I hate to ask, but how much did the brain cost?

Edward

Todd B

The ABS-ABD brain was $730 from the one of the dealers in the area that provides a PCA discount. I did find a place where I could get a recondition one for $450. But with a DE looming next weekend I didn't want to take a chance on something being wrong with the brain. My other thought on the reconditioned unit was the age of the electronics, not sure if that would be an issue.

Todd