Troubleshooting slow braking - now abs?

[Hoffbrohaus]

Funny I knew you guys were going to ask. I plan on working on it this weekend. Sorry I was in Mexico for 10 days

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[Wh33lhop]

You could have a bad ABS module or one or more weak/bad rear wheel sensors.

This would be my bet as well.

[Hoffbrohaus]

I finally pulled the rear abs sensors and cleaned them. I think it's better. I need to drive some more to test it. But stopping from 60mph engages abs slightly now. It wouldn't activate at all before. And stopping distance seems normal although I feel like no abs was better but I will give it time.

Check out the passenger side sensor though. After I cleaned it I could see some build up that I can't get off. Looks almost like JB weld. Compared to the driver's side rear you can really see the difference.

Dirty passenger side sensor


Cleaned passenger side sensor


Cleaned driver side sensor


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[jlevie]

I'd say that the sensor with the stuff oozing out (probably potting compound) needs to be replaced.

[Todd Black 88]

If there was any problem with the sensors, wouldn't it illuminate the light on the dash?

[Hoffbrohaus]

If there was any problem with the sensors, wouldn't it illuminate the light on the dash?

Right. That's what I was wondering too. I have no dash warning lights

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[jlevie]

Right. That's what I was wondering too. I have no dash warning lights

If the sensor isn't working at all you will get a light, but if it is missing pulses you'd get ABS activation. This being a rear wheel sensor the symptom of ABS activation will be a hard pedal and reduction in stopping force (Ice Mode).

[whitewatermd]

If the sensor isn't working at all you will get a light, but if it is missing pulses you'd get ABS activation. This being a rear wheel sensor the symptom of ABS activation will be a hard pedal and reduction in stopping force (Ice Mode).

jlevie, i have a similar situation, however the abs is engaging when the car is almost slowed to a stop. the pedal feels firm, which i actually like, however i cannot seem to get rid of the engaging. I have replaced all of the abs sensors, and i think i have narrowed it down to being the right rear sensor, which has been replaced, but im still getting the pulsing. if i go out to a quiet road, get up to about 40 and slam on the brakes, the abs works perfectly. i just cant get rid of this pulsing when stopping. i actually noticed this morning, that it pulsed even after the car had stopped... help!!!

[Todd Black 88]

Any more updates?
Did cleaning the abs sensors solve your issues?

[Hoffbrohaus]

Wow sorry I thought I updated this thread. Yea that fixed it right away. Cleaning the sensor and reinstalling I could brake fast and engage abs.

In the months that followed I have noticed it starting the slow braking symptoms again. So I bet jlevie is right and if I pull that sensor again it will be oozing potting compound. I have been looking on the classifieds for a known good sensor.

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[Todd Black 88]

Cool, I will check my sensors and see how it goes.

Thanks again

[Liquidity]

On the track this happens occasionally if you hit the brakes while bounding over a gator. If the timing is such that a rear wheel is airborne then the brake can stop the rear wheel from turning (LSD plays a role here), ABS pump reduces pressure to the rear, brake pedal goes hard, and driver shrieks in horror.

Our car's brakes are very front biased. The slave cylinder creates a 2/3 to 1/3rd bias, and the bias valve, active over 250-300psi depending on who you talk to (light/med foot pressure), adds another 2/3rd to 1/3rd beyond that. As a result, your rear wheels should never lock up before your fronts. I've put hugely more aggressive more pads in the rear vs. front, but I was never able to equalize braking forces on the track. It takes more then pads to make up for all that bias.

So why on god's green earth would anyone choose to keep the ABS system in their race car if its this horrible???

[Hoffbrohaus]

I have been looking on the classifieds for a known good sensor.

Bought 2 rear abs sensors and replaced my faulty sensor. Everything works as it should now. I have one extra if anyone needs one.

btw I bought them off an early model and apparently there is a difference. My late model had a cover over the length of the wire, the early model did not. Still works.