I have a friend that has an '89 that is used for autocrossing, at the last event of his season last year he started to have an ABS problem, it seems like they would get an ABS light and one or more wheels/tires would lock up, like the ABS had failed at that/those wheels.

Anyone have any ideas?

Anyone have an ABS module/manifold at a good price?


vettmike

 

ttt

 

Honestly it can be anything from the simple, a bad connector or ground to a completely shot ICU ("ABS module").

Having just some wheels lock-up and others not is not odd even without ABS.

It sounds like they're not getting any ABS activation, can you get fault codes?


For a tracked car it most likely, a wheel speed sensor (WSS) or tone wheel since they get beat up. But without a minimum of the fault codes to at least get a basic idea of where to look it's difficult to even start.


They can do a basic visual check of the WSS, the wire and connectors.

Here's a post that's along the same lines, though on C5's, but basically applicable.

http://forums.corvetteforum.com/show....php?t=1015582

 

The 89 ABS controller does not store or display codes. The 86-89 ABS systems are all pretty much the same and not as advanced as the later ABS systems. An ABS light on while auto-crossing could mean the ABS was activating, or that the ABS system was seeing a problem. From your description the ABS wasn't activating, so it must have seen an intermittant problem.

I think Mighty-Mouse has it figured. "For a tracked car it most likely, a wheel speed sensor (WSS) or tone wheel since they get beat up." The wheel speed sensors used on the 89 are in essence simple, but powerful magnets. An AC current is induced in the sensor by the passing of a toothed wheel located on the axle or wheel bearing (depending on the location front/rear) as the wheel turns. The ABS controller uses the absolute voltage and the wheel to wheel voltage differential values to decide if a given wheel is in a skid or lock-up condition.

The easiest test/fix is to remove the sensors and clean them. Each sensor is mounted in the wheel knuckle and held in by a 10mm screw. Very easy to remove and clean. Being powerful magnets they pick up lots of tiny road debris over time which affects their ability to sense the toothed wheel. Just get a ratchet and socket and unscrew the retaining screw. Pull the sensor out and clean with WD-40. Apply a thin coat of anti-seize compound and re-install. If that doesn't fix it, email me and I'll send you a more complete write-up on troubleshooting the early C4 ABS.

 

Sounds like his brake fluid level is low.

Had that happen to me at a few autocrosses, the ASR/ABS lights would come on and bye-bye abs. How annoying.

I added about an ounce of brake fluid (broght the level from just under the line to just above the line) and never had the problem again.