Re: C4 Brake Problem
Michael------
There's actually a few other possibilities, too. First of all, there's the ABS modulator valve. This is a motorized valve that re-directs braking effort when it receives the signal from the ABS control module. The ABS control module (the component the dealer suggested was the culprit and for which I previously provided information) is a completely "solid state" device and it is completely separate from the modulator valve. The modulator valve is anything but a "solid state" device. It has many "moving parts" and "fluid channels".
The modulator valve for 86-91 Corvettes, originally GM #14084081, later GM #14105966 and last available under GM #12506759, is discontinued. When discontinued, it carried a GM list price of over $1,700. I know of no source for a rebuilt or repaired valve assembly.
Neither the ABS control module nor the ABS modulator valve are the sort of parts that one wants to replace on a "shot-gun" basis. Not to mention the fact that they are both discontinued, extraordinarily expensive and difficult to locate, they are both electrical parts. That means that they are not returnable under the policies of virtually all automotive parts suppliers.
There is a available a publication called the year-specific Corvette Service Manual. Dealers have copies of these but OFTEN neglect to ACTUALLY USE THEM. Using the manual, the problem can be diagnosed using a well-defined protocol. I certainly hope that the dealer performed this as part of their diagnosis of the problem being with the ABS module. If their instruction that the problem was with the module was a "guess" as the next round fired in the shot-gun approach, that could generate another round of unsuccessful repairs. However, this round will be considerably more expensive than the first.
Another possible problem which should be checked is to determine if there is any damage to the TBW brake line supplying the affected caliper. These lines are well shielded from damage. However, "klutz" mechanics could probably find a way to damage them during vehicle lifting or jacking procedures.
In any event, this episode just reinforces what I've said many times before: C4 Corvettes are the most complicated Corvettes ever built. Their repair and restoration makes work and restoration on earlier model Corvettes virtually child's play.
Michael------
There's actually a few other possibilities, too. First of all, there's the ABS modulator valve. This is a motorized valve that re-directs braking effort when it receives the signal from the ABS control module. The ABS control module (the component the dealer suggested was the culprit and for which I previously provided information) is a completely "solid state" device and it is completely separate from the modulator valve. The modulator valve is anything but a "solid state" device. It has many "moving parts" and "fluid channels".
The modulator valve for 86-91 Corvettes, originally GM #14084081, later GM #14105966 and last available under GM #12506759, is discontinued. When discontinued, it carried a GM list price of over $1,700. I know of no source for a rebuilt or repaired valve assembly.
Neither the ABS control module nor the ABS modulator valve are the sort of parts that one wants to replace on a "shot-gun" basis. Not to mention the fact that they are both discontinued, extraordinarily expensive and difficult to locate, they are both electrical parts. That means that they are not returnable under the policies of virtually all automotive parts suppliers.
There is a available a publication called the year-specific Corvette Service Manual. Dealers have copies of these but OFTEN neglect to ACTUALLY USE THEM. Using the manual, the problem can be diagnosed using a well-defined protocol. I certainly hope that the dealer performed this as part of their diagnosis of the problem being with the ABS module. If their instruction that the problem was with the module was a "guess" as the next round fired in the shot-gun approach, that could generate another round of unsuccessful repairs. However, this round will be considerably more expensive than the first.
Another possible problem which should be checked is to determine if there is any damage to the TBW brake line supplying the affected caliper. These lines are well shielded from damage. However, "klutz" mechanics could probably find a way to damage them during vehicle lifting or jacking procedures.
In any event, this episode just reinforces what I've said many times before: C4 Corvettes are the most complicated Corvettes ever built. Their repair and restoration makes work and restoration on earlier model Corvettes virtually child's play.
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