when i hit the brakes i hear a rhythmic clicking sound coming from the dash. Sounds like its inside the cab but i could be mistaking. I know its not u-joints or suspension. Could it be a stuck relay? This does not happen every time i hit the brakes only about 50% of the time. My abs/brake light comes on occasionally but turns off after i restart the truck. just replaced my abs sensor on the rear diff and now this.

 

Check fuses to see if a previous owner installed a circuit breaker. They click about once every 2 seconds when they self reset. If that's the case, then most likely you have a short in the wiring somewhere that will probably be difficult to locate. I had a pickup once that had a short right where the wire goes into the bulb socket. Good luck.

 

could be the abs unit under the hood going bad

 

mine does the same thing. been doin it for 5 years, I never found out what is so I just put electrical tape over the lights on the dash. every one thot I was nuts about the ticking, so I learned to live with that as well. I'm gonna keep following this thread to see if you have better luck than I did finding the prob. GOOD LUCK

 

Mine does the same thing every once in a while, and I don't really know what it is...I just don't want the brakes to fail and rearend someone!

 

Clicking from under the dash - as if behind the ABS warning light, right of column. Happens just sometimes now. Some of those times, it corresponds with brake pedal feeling as if half the system isn't functioning. I'll watch here to see what expertise shows up.

 

In my case, I think I found the embarrassingly-dumb problem: hyd pump reservoir way down!

I don't feel TOO lame about this, although maybe lazy, since it sure would have been easy (even 'routine') to check my PS fuid reservoir for general maintenance. I'd not bothered with this, since I had figured any concern with low "steering" res fluid would show up first as the standard loud whiny "pump-wants-fluid" sound, especially on heavy steering demand. But not so in this config, for some reason - my brake issues never coincided with any steering problem, ever, in fact.

When I finally got to checking it, the res was about half empty - no reading on the stick. I took the trouble to pump out and replace all fluid with ATF (I'm in a warm climate, and an industry chemist once assured me the best hydraulic fluid available anywhere is ATF, meeting or exceeding any PS or other hydraulic-fluid standards) and in the month since, there's been no clicking or brake lights.

In hindsight, much could be explained by the low-fluid issue. I'd hit the brakes in semi-panic mode, and the result would be this nasty two-tiered response - limited braking at first, followed by grabbing and heavy clunking from the rear. What I conjecture was happening was that the low pump res level would result in sufficient sloshing in the res, especially in some manner on braking, thus starving the brake booster momentarily - until more fluid could enter the pump and recharge the booster. Still, I would think it would be engineered to provide preferential pressure to the brake booster (I'd rather lose steering ease than brakes...) but this experience suggests otherwise.