Front Brake Caliper problem and diagnois

[ptf18]

What are the symptoms of occasionally "sticking" Front brake caliper pistons?

On occasion, I get "pulsating" feedback into my brake pedal (actually you can feel the truck "pulsate") as if the rotors are warped. They are not warped as I have checked them with a dial indicator....less than .003 R.O. A through visual inspection of the rotors, calipers, brackets (sliders pins are clean and lubed), hoses and pads reveal nothing unusual.

Thoughts? 245K miles on the truck (and calipers)

 

[CorbinsRanger]

ABS gone wonky?

 

[4.0blue98]

Pulsing while braking could be some contaminant on the rotor. Common when doing a break in. Try an aggressive stop or several from about 40mph or so and see if it clears.

 

[rusty ol ranger]

If the calipers occasionally stick...it could be the brake hoses themselves.

Sometimes the inside breaks down to where the hose wont leak, and when you put the pedal down the fluid goes to the caliper, but theres not enough pressure to release the fluid pressure. If that makes sense. Basically a broken down piece of rubber acting as a one way valve inside the hose

Ive had it happen, never noticed a pulse though. But it could be the fluid is hitting resistance in the hose on the way down and forcing its way through...i could see that causing a pedal pulse

 

[Uncle Gump]

Typically a warped rotor will always pulse... not intermittently. Something else that will happen is you can feel a warped rotor inthe brake pedal as it will slightly rise and fall.

If it is truly intermittent it has to be related to temp of the system or related to pedal pressure.

If a caliper piston or slide is sticking there is an associated drag... this will cause heat.

What are the driving conditions when you notice it?

 

[pjtoledo]

at your mileage it's time for new hoses.
are the pads wearing evenly?
one trick I use on calipers is to push the pistons most of the way out then back in a couple times.
put a block of wood in the caliper then pump the pedal, don't go too far and pop the piston out.
open the bleeder to expel the bad fluid before you push them back in.
rust forms behind the clips and jams the pads, sand/chip away the rust so the pads can move.

how old are the rotors?
after a few years and thousands of heat cycles the metal changes and looses it's friction ability, not necessarily evenly around the rotor.

 

[ptf18]

Thanks Fellows. I should have added.....

I notice the occasional "pulsating" after I've driven the truck (and used the brakes) for....a little bit... maybe 10 miles or so. BUT just occasionally. Bottom line... I'd have to say this issue occurs after the brake system has warmed up.

Don't notice it when just starting out on a trip or just a short distance trip (less than a...few miles) Can't say about outside temperature affecting this problem as I haven't "paid attention".

ALL Front brake components are 20 Y.O. with 245k miles on them...Except the pads which have alot of life in them and are worn evenly (I pulled all 4 out when I inspected the Front Brake system)

I change my brake fluid every 30k and have since I bought the truck new in 2002.

Hoses appear to be in good condition. No swelling, soft spots, leaks, etc.

With 245k miles on the truck (and the the entire brake system) I have on hand ALL new brake parts INCLUDING: M/C Rotors & new bearings/seals, Raybestos Calipers, M/C hoses. Same with the rear. M/C drums, M/C Hoses, Raybestoes cylinders, Brakes shoe hardware kits, etc.

So.. I could just put on ALL the new parts and hope this "pulsating" problem goes away BUT...... You all know how that can go.....

I'd like to be pretty confident that throwing ALL these new parts at the truck fixes this problem....

ABS maybe????? Hope not....

 

[Uncle Gump]

If it was an ABS issue you would hear the ABS system activate.

With 245K miles... you checked run-out but did you check thickness? I would think they would be worn to minimum spec or even under. Heat generated could very well be affecting your system.

I personally just make the time and install the new rotors at a minimum.

 

[pjtoledo]

my 2 cents says you have a slight rub on only part of a rotor, as you drive that spot heats up and grabs where the rest of the rotor doesn't.

friendly fyi, hoses swell on the inside.