s-10 back brakes lock up when get wet

[imageine]

Hi, my son has a 1998 chevy s-10, whenever it rains the back brakes when he applied the foot pedal lock up, it only does it when his truck is driven in the rain, we are so frustrated, as we can't figure out what is causing this problem, and really at this time he can't afford to take it in to a specialist, you help would be greatly appreciated, or any advice on web sites etc we might be able to locate the cause of this. Thank you

[sector95]

Does the truck have anti-lock brakes?
Some trucks had A/B only on the rears but I think yours is probably new enough for it to be 4 wheel anti-lock brakes.

Does the truck do this *every* time you brake when it's raining or just the first time?

When was the last time you checked the rear brake linings (for wear) and wheel cylinders (for leaks)?

mike

[imageine]

Hi and thank you for your reply, I made an error on the age of the truck it is a 96, not a 98, oops, yes the truck does have anti lock brakes.
The truck does this everytime you brake when it is raining.
We recently took the rear tires off, etc, and checked the brakes, they are in excellent shape as far as wear and no leaks, but just can't figure out why it is doing this, please help.....

[imageine]

One more thing, when you put the brake on, the rear ones lock up, then the anti lock brakes kick in, it didn't do this all winter, but now is, but only when it rains, and they get wet, apparently the snow in the winter didn't have this effect on it, he bought the truck in the winter time, about 3 months ago.

[sector95]

I would start with electrical connections. There are sensors for the anti-lock system to indicate wheel rotation (or a locked condition). On the front, each wheel has a sensor but for the rears there may be just one sensor (possibly taken off the drive shaft... if the wheels are locked the drive shaft isn't turning).... I don't have my shop manual in front of me so I can't say for sure.... Since this only occurs when it's raining, the electrical connection(s) for the rear sensor(s) may possibly be getting wet.... even just a little dampness can cause problems. Check the connections: carefully seperate the connectors, give 'em a squirt of electrical contact cleaner (this will dry and clean them), get some silicone grease and give the rubber gaskets on the connectors a swipe, reassemble and see what happens.

Something else to consider: replacing the brake fluid is actually a recommended maintenance item...and is especially important for anti-lock systems... but something few people ever do. Most good auto shops have the machine that will purge all the old fluid and replace it with new fluid... and in the process bleed the brake system. The service, I would guess, will set you back $75.... but it is worth it.

Usually, within the first few minutes of starting, the anti-lock system does a self test; you'll hear the small motor that is part of the system run briefly. Does the system self test? Is there a seperate light for the anti-lock system and is it on?

[imageine]

Thank you for responding, and so quick.
We will definately try your suggestion, we beleive it is something to do with electrical, as it only happens when it rains, their is no light on for the anti-lock system, and when you first start up the system does not self test itself, at least we can't hear it doing that, my other vehicle was a 98 cavalier and it used to self test, I remember hearing it, thank you again. Going to check to see if this is it.