OK, so for the past week, after the truck sits for a while, the brake pedal travels approx. 2 times farther than usual for the first pump. Seems fine for the rest of the trip. Occasionally travels said 2 times farther when not used for a while, like driven for ~10 miles on the highway. Most of the time they are fine though after traveling 10 miles or more.
I did notice a clunk the other day when approaching a stop light, kinda like brakes were not working and then wham, they were there, but I could not tell if it was both or one axle. That has not happened since.

Was at a friends house 2 nights ago, backing up to turn around and stepped on the brake pedal, it went all the way to the floor.
~5 seconds later, the ABS/Brake lights come on, had to pump up the brakes to get pressure, 2 or 3 times.

So far, the pedal travel has been normal since. Lights were on during the first trip of the following day, after shutting down and starting up again, lights off and pedal seems normal.

I am wondering if perhaps there is something up with the master cylinder?

I do need to check/replace the pads. Quick visual shows that outside rears are getting thin, haven't taken the tires off yet to get a good look.

I did make it 77,000 miles so far on the pads, so no complaints there.

Just wondering if the general consensus is that there is something up with the master cylinder or if this is perhaps because of bad pads.

Fluid level was above min level (not all pads are shot...)

Also, I do have the p5000/e1693 code, looked in the forums and saw that the most likely culprit is the rwss.
Will the on/off/on/off/on trick show stuff for ABS or not?

One more thing. I did have an ABS module replaced by the dealer because anytime that the temp got >-10 the ABS system would not function, brakes worked, but no ABS. (I actually kinda liked that better than 2 wheel ABS, no problems stopping when ice under one side of truck and good tar under the other...)

Sorry if it seems like I am rambling had to type this quick before I leave for a couple of days.

Truck is:
2001 2 wheel ABS (wish it was 4 wheel)
4WD
77,000 miles
Quad cab, bone stock.

 

Sounds like air in the line to me. Have you been under it to check for fluid leaks especially at the rear wheel cylinders? Assuming of course that it has drums on the back. Did you check the level in the master cyl warm or cold? The fluid shrinks some when it gets cold. Could be it gets below minimum after it sits for a day.

 

Its 4 wheel disc, yep, checked for fluid leaks. I checked when warm, but it was plenty high, it wouldn't contract that much...

 

I had a car with about the same problem. The brake pedal would go to the floor, pump the pedal it would be fine. Then 3 or 4 days later would do the samething. Mine was always after it had been parked, 1 hour or longer when it would happen. After 2 months the master cylinder started leaking, replaced the master cylinder problem solved on the car. This car didn't have abs brakes.

A P0500 is vehicle speed sensor malfunction.

On the 1693 you will need to have codes pulled. Autozone and some other parts stores will do it for free.

With that many mile I would check the rear pads.

Hope this will help you some.

 

It sure sounds to me like the master cylinder is getting ready to take a dump. If I were you I would either change the master cylinder or find somebody that can. It ain't no fun to loose all your brakes!!!!! (Yep, I know from experience).
Tom

 

i had the same thing on by 2002. it turned up to be a rear inner pad that had seperated. it was broke off the steel backing and it was uneven so it would push the piston a little further back in the caliper. when it dropped into place it would require a pump of the pedal to get it up high. i pulled the wheels and thats what i found. it just started one day and maybe one out of ten times i would have a partial loss of pedal.

 

Your symptoms are very typical of the master cyl failing. I wouldchange that first. Check the pads and replace them if they are getting low. The master cyl probably set the codes. If the codes appear after the repairs then do diagnostics again.

 

it makes more sense to do a brake inspection at the wheels before you start changing parts for no reason other than a guess.

 

Mine did the same thing. light came on and everything. replaced speed sensor and everything is ok now.


-Kyle

 

Well, I found the reason for the pedal hitting the floor, the inside left rear pad seperated from the backing plate, I assume that it fell out when the pedal hit the floor. The right rear inside pad also had seperated, but had not fallen out.

Now I have a new problem. I pushed the pistons back in with the right tool (forget the name). Started with the driver rear, then driver front, pass front, pass rear.

I suppose that I was supposed to pull a relief valve or that I did it in the wrong order.

I have the front left brake, when I step on the pedal, it pulls left. That seems to be about it.

All rotors were turned, new pads all the way around, new pin boots for the rear, permatex(?) lube for brake pins, it was green.
(Wondering if I should have used Lithium or something as that seemed to be what was in there?)

Anyone have any ideas?

 

The lubricant you used is fine. Look at all the pads very carefully and make sure the ends of them are straddling the rails where they slide, and not hung up on the end of one. Hope this makes sense. There is no relief valve to pull, but when I squeeze back a caliper piston, I usually open the bleeder screw to let the fluid out, so as not to push the dirty fluid back up to the master cylinder. Probably not an issue here though.

 

I understand what you mean about the pads catching...
I will check that when I get a chance (tomorrow hopefully).
We have just a bit of snow here, and I did a test. I can stop the truck by stepping on the pedal while idling (with the front brake(s?)) and the rear keep spinning, this is in 2nd gear (6 sp tranny), it SEEMS like there is no pressure going to the rear brakes.

This is a 2 wheel antilock brake truck. Just want to make sure that there is nothing special to do.

 

starting a new thread, this is kind of long...
Also, I was tired, crabby and not thinking clear so I left out some details...