On wet days the rear brakes will make a loud clunk sound and lock up the first few times they are applied. When the brakes lock, of course I instinctively release the pedal, but the brakes remain locked until the van comes to a complete stop. Sometimes they release immediately upon coming to a stop. Other times, they won't let go for upwards of 30 seconds. I bought the van used and was told that the ABS pump had been out for years. The ABS fuse had also been pulled. However, the dealer says the ABS system cannot be fully disabled (whatever that means).
Everything I have read says that the first time the brakes are applied, the ABS system does a self test (which may be accompanied by a clunk sound) and can disable itself if the test isn't nominal, thereafter working as a conventional brake system. If the ABS system can disable itself, why can it not be permanently disabled? If, in fact, it is disabled, then why don't the brakes release? The dealer attributed it to the "front springs and 'something' in the ABS system," whatever that means.
I've seen the following causes of brakes locking on this and related vehicles (including the Dodge Caravan)...
1) Sticky Calipers 2) Sticky Pistons 3) Sticky Master Cylinder 4) Some kind of restriction in the brake fluid lines 5) Sticky ABS relayAnyone seen these symptoms before or have any ideas?
By the way, the occurence appears to have more to do with wet roads that any moisture in the system, since it is independent of whether or not the van was in the garage or left outside, but I could be wrong on this. Maybe it's both. Thanks.