SLAYfriknBODIES

I have a 1993 pickup that has developed an odd pattern of noises when I brake.

If the radio is on, you don't hear the noises- that's how faint they are but they still bother me because I have never heard another vehicle make them.

Its hard to pinpoint where it comes from too. My mind imagines them coming from the master cylinder or something in the brake system but it seems to eminate from the center of the back wall of the cab.

The sound itself is like either rice krispies popping in milk and a coffee maker combined. Just a soft ticking pop noise. My braking is unaffected and the truck drives fine, but before this "shrug off" turns into the onset of a serious problem, id like to solve it or at least figure out what is making it.

When the truck is parked, stepping on the brake pedal does NOT produce this noise. It has to do with the vehicle in motion.

(This noise is also only made when the vehicle is coming to a stop. using the brake to decelerate slightly while in motion doesn't appear to make the noise, though engine noise could be drowning it out.)

Gamefreakgc

Check your brake booster line for any damage or loose connections.

Also, you might want to check/change your brake fluid by bleeding your brakes (and master cylinder if you've ever taken it off), it might have sediment or air trapped. That's a regular maintenance item anyway.

Those aren't sure fixes by any means, but with that vague of a problem you have to start somewhere.

wyoming9

iTrader: (1)

I had the heat shield on the cat coming loose making a sound like you describe .

If the heat shield is still on the exhaust where the down pipe is could be that.

Just a harmonic vibration caused by tires the road your on.

could be caused by something against the back of the cab.

What shape are your brakes in ?? Pads and shoes still have enough lining left??

Rotors and drums not warped ??

no known fluid leaks??

SLAYfriknBODIES

Just did a brake job about six months ago. new rotors, pads and calipers on the front and had the guts of the drums replaced with a hardware kit.

I'm willing to bet it is something to do with the master cylinder. I started replacing vacuum lines yesterday on the injection manifold and its already bringing my engine up from that "sluggish" old engine feeling. I'm just gonna keep going with all of the other hoses until everything's swapped.

The Haynes manual diagram doesn't show a bleeder screw on the master cylinder and I can't seem to locate it. Where is it exactly?

stinkfoot

Try jacking up the rear end and running it. See if you can replicate the noises. Might be ineffective since you don't have the weight of the vehicle pushing against the resistance of the brakes.

If you're developing good pressure in your master cylinder, you're not too likely to get any air out of it, although it is definitely possible. I'd look at other symptoms. The only difference between braking with the truck sitting still, and the truck moving is that the rotors are turning.

The bleed screw will be right on the body of the cylinder. If you can't find it, I supppose it's possible that it's been capped (not sure why anyone would do this, or it didn't get installed on the MC when it got installed).

wyoming9

iTrader: (1)

There is no bleeder on the Master Cylinder .

At least that I ever saw.

stinkfoot

Good to know. I've never even looked at mine.

scope103

Did you use 'Brake Lube'? http://www.autozone.com/autozone/acc...er=526715_0_0_ This stuff might just be snake-oil, but the idea is that you put it between the caliper and pad to eliminate brake squeal. You might have a very slight "squeal," and this stuff might be what you need to stop it.

Alas, I can't think of any way to diagnose the squeal, other than take it apart and put it back together.

SLAYfriknBODIES

well, i stand corrected. The noise is emitted when I shift the transmission into neutral and let the truck decelerate. The noise begins before I apply the brakes. Its a very gentle ticking pop; almost like the sound of a hot engine cooling down- but much more rapid.

SLAYfriknBODIES

I'm actually guessing its my driveshaft out of whack. I remember while trying to hammer U-joints out in the dead of night a year or so ago with a buddy we put a slight dent in the side of the driveshaft which, in retrospect might have thrown it out of balance enough to wear out one of the U-joints so now it grumbles as it winds down.

I'm going to pull my rear drive shaft and test it in H2 on the front shaft to see if the noise persists.