Low/No Brake Pedal

roadrunner · Post by **roadrunner** » Fri Mar 14, 2008 7:44 pm

I've been having a problem with my 01 CC for quite a while now and am looking for suggestions how to overcome it.
When I drive on very rough/rutted/washboard roads my brakes seem to "bump back". What I mean by this is the pedal will go clear to the floor unless you "pump" the brakes back up. This never happens on paved/smooth roads only on really rough ones. It acts like you had pushed back the caliper pistons and have to pump them back out to get brakes. I've replaced all 4 sets of pads twice since I got the truck. Actually the rears more than that and the problem is consistent. Have also replaced all guide pins and boots with no change in this condition.

Also has anyone figured out a fix for sagging emerg brake cable. When driving in freezing weather in mud or snow buildup will accumulate on emerg brake cable causing it to sag and wear out e-brake shoes prematurely. Only thing I've come up with so far is to plate over the body bottom on the drivers side thus enclosing the cable. Not real anxious to do that.

roadrunner · Post by **roadrunner** » Sun Mar 16, 2008 3:54 pm

I see lots of people been viewing. No suggestions anyone??

F9K9 · Post by **F9K9** » Sun Mar 16, 2008 4:34 pm

This is a new one on me. I would look for answers from Brule or Steve on this one. If, I didn't have this forum and was left out on my own, I'd look at replacing the brake line synthetic components. I might even suspect the master cylinder first. I guess I am a wimp and rely on our resident experts a little to much.

purduecrew · Post by **purduecrew** » Sun Mar 16, 2008 4:39 pm

yah know, I had my brake pedal go to the floor on me last saturday coming to a snow convered intersection

I think I just have a vacuum leak. Maybe thats the case for you too, in that all the jarring disturbs an otherwise "sealed leak"....

roadrunner · Post by **roadrunner** » Sun Mar 16, 2008 5:26 pm

Interesting suggestions. Reed, I don't think it's the hoses or cylinder. Solid good pedal all the time except after bouncing around. Then full stroke and nothing or next to it. If you anticipate it and give a few short pumps before trying to brake you can feel it improve with each stroke. Thanks though.

Purdue, I've pulled both the master cyl and booster and checked all lines and hoses too with no discoveries. Holds vaccuum and installed a guage to verify no loss. All okay. Thanks as well.

I know this will sound odd but is it possible for the front or rear rotors to move out of perpendicular enough to act like a pry-bar moving the pads apart thus requiring fluid recovery on application?? I had considered the rear or fronts moving laterally but the calipers should float with that motion and they are all free moving and able to do so.

Doesn't appear to be anything out of order with the ABS either. Functions normally and I had a friend with a brake capable scanner (mine isn't) check for codes or history codes with none found either.

All I've ever noticed is the problem appears quicker on rutted roads as opposed to just rough or washboardy.

Anybody else with any suggestions??

rlrnr53 · Post by **rlrnr53** » Sun Mar 16, 2008 6:12 pm

A vacuum leak usually results in an extremely hard pedal. I have seen master cylinders cause this type of problem.

F9K9 · Post by **F9K9** » Sun Mar 16, 2008 7:14 pm

Our rear calipers are known to lock up. That may not be related to your problem but, it is something to lock at. I have found mine frozen 2x already and replaced the slide pins and use synthetic grease on them. Why it is happening, I do not have a clue. It is just a thought.

Post by **HenryJ** » Sun Mar 16, 2008 7:24 pm

Yours is a 2001. How many times have you changed the fluid?
I live in a very dry climate and have changed mine three times over the last seven years.
Brake fluid is hygroscopic. The increase in water content changes the boiling point and hydraulic properties.
While this is not good for the fluid , it is good for the system as the contamination is suspended. This has a limit though eventually the system degrades.
My question was to perhaps determine the condition of the system.
The only other areas of question have been asked. Keep in mind that vacuum leaks in places other than the booster can have an effect as well. Check out the little short pieces of line behind the booster for dry rotting. Check the reservoir for cracks.

Sorry , no help here.

Torskdoc · Post by **Torskdoc** » Sun Mar 16, 2008 9:35 pm

I'm thinking more along the lines of the ABS being too sensitive.

When I'm braking coming up to this one left turn onto the interstate on the overpass, when I come to the expansion joint(there is a 1/2-1" drop off at the joint) at the end with the brake on, the pedal goes down and I can hear the ABS cycle on until the wheels grab hold. I usually anticipate and brake hard before the joint and back off over it. OR I just push down harder to the floor and pray I donn't hit the poor SOB driving that Soccer mom mobile in front.

Larry

green02crew · Post by **green02crew** » Mon Mar 17, 2008 5:41 am

I have had similar things happen like Torskdoc described when on really bumpy terrain where the tires may not make full contact with the ground and I get results such as what you have for a problem roadrunner. I don't know if that helps at all but it does sound familiar.

roadrunner · Post by **roadrunner** » Mon Mar 17, 2008 1:59 pm

Rlrnr53, I've confirmed both master cyl and booster working okay and my problem is total or nearly total loss of pedal. Thanks though

Reed, Yes I too have been down the frozen caliper pin road. Also have replaced pins etc and synthetic lube. Hasn't had any effect on the problem though. Thanks as well

Brule, I've done a complete flush change twice since buying the truck usually at brake job time. And Yes I know brake fluid draws moisture hence reduced boiling points when contaminated. As to the vaccuum leaks I teed in a vaccuum guage at the booster, actually sensing vaccuum reserve in booster only, and all is well there. No significant loss there. No cracks or dry rot found either. Thanks for the suggestions though.

Larry, I too have experienced the dreaded ABS no brakes when you really want to lock em up syndrome. Usually in mud on ice or washboards or in loose gravel. This is different though. The pedal will literally go to the floor with no braking at all. Just as if it were unhooked. Quite thrilling in a panic situation. Make that double panic cause of the no brakes. I can also tell when ABS is active too as it will make an audible, for lack of a better word, sqwonking noise and if active long enough even creates light audible hiss in the radio even on FM. When the ABS is active I still have pedal albeit squishy feeling but pedal nonetheless. Thanks for your suggestions as well.

Green02crew, as described to Larry above ABS is working and during it's operation additionally to what I told Larry the pedal feels like it pulsates. Not like a bad rotor just more of a sensation that it is in concert with the sqwonking sound. Thanks for the help.

As an additional note I wish to thank all who've offered suggestions and will continue to look for the problem. If any other ideas come to anybody please share them even if you feel them ridiculous. In my years of wrenching I've seen some pretty odd solutions to perplexing problems. Also I wanted to add I am running stock aluminum spoke wheels and 235x75x15 tires and no wheel spacers (yet). Just thought I'd throw that in in case anybody was thinking of increased wheel leverage problems. Thanks again Larry

AZS10Crew · Post by **AZS10Crew** » Tue Mar 18, 2008 9:58 am

Let me apologize in advance if these suggestions are redundant or seem silly...just trying to make some guesses based on what I've seen with other vehicles with similar problems in my last job as a service writer.

Check to make sure the spring clips are installed correctly onto the pads. We had an Escape in the shop with a problem similar to yours that got a new master cylinder, booster, and several items on the house because we couldn't fix the problem. Finally gave it to another tech in the shop who found a problem with the spring clips not installed correctly onto the pads. (wrong ones or not on right...can't remember...it was about 9 months ago).

Are pads at a good level? Have you removed the caliper to check? We had a car in the shop once that had the incorrect rotors installed (1/2 diameter too small) and when looking at the pad levels with the rim off from the outside of the caliper, they looked brand new. But once the caliper was removed, you could see where the pads were down to metal except for the outside 1/4" where a lip had formed around the too-small rotor. Low pad level can cause a soft pedal as well.

Again...just throwing guesses out there, not second-guessing your diagnostic abilities.

roadrunner · Post by **roadrunner** » Tue Mar 18, 2008 5:06 pm

AZS10Crew, Yes spring clips are in correctly. As to pads they've all four wheels been replaced twice and the back an additional two times. The problem is consistent throughout pad wear cycle. Rotors are still originals and of correct diameter. Pads do not overlap rotor edges. Pedal has not been soft. Has been non-existent when having problem. Best I can describe it is as if you had just pushed back one or more of the pad sets and had to pump fluid back into caliper cylinder to recover pedal use and ability to brake.
Additionally all caliper pins and mounting brackets have also been replaced and pin boots as well. System flushed and bled to make sure air was removed twice. Problem remains unchanged throughout all these procedures. Rough road (especially rutted road) equals loss of brake ability.

No need for apologies. No need to think I would be offended or presume second-guessing of diagnostic abilities either. I'm up against a stone wall to explain or repair this problem. That's why I went searching for any and all help and suggestions from the forum. Many here have owned their CC's longer than I have had mine and I was just hoping someone else might have also encountered this odd problem. No offense will be taken no matter what the suggestion or who makes it.

PATRICKH · Post by **PATRICKH** » Wed Mar 26, 2008 12:31 pm

I've have this problem too. Checked the vacum, pads, rotors, replaced all the hardware (pins, boots, sliders) still have the soft pedal.

My father in law was a mechanic in So. Cal. for 25 years and he has suggested flushing the ENTIRE system of all the old fluid. He remembers having this problem on some of the first S-10's in the 80's.

Now, just have to find a warm day and time off to do it.

roadrunner · Post by **roadrunner** » Wed Mar 26, 2008 5:14 pm

Patrickh: Your problem may be a little different than mine. I have solid good pedal all the time until I "bounce around" in ruts or rough roads then pedal goes all the way to the floor. Pumps up and works okay after that but quite a shock when you first "go for it" and have nothing. I have already flushed my entire system twice. Let us all know if you find any "weird problems" on your brakes.

Horsehammerr · Post by **Horsehammerr** » Thu Mar 27, 2008 1:46 am

It's 4 am in Missouri, so a little dark to even look before I speak. It seems to me the only way you could loose all pedal pressure in a rough road or bump moment would be if something disconnected. Is it possible for anything from the Pedal assembly to the brake pads to come loose then pop back together ? I mean anything mechanical or electrical. There is both in our systems. Stuff like this makes me lose sleep trying to at least dream up a solution. I'll probably be tearing my system apart this weekend looking for possibilities.

PATRICKH · Post by **PATRICKH** » Thu Mar 27, 2008 3:45 am

Yeah roadrunner I have a good pedal too, except for when I get it on rough roads or off road. So flushing didn't work ??

I am kind of agreeing with horsehammerr in wondering if something electrical is to blame. A loose ABS sensor??? (think henryj mentioned this above) I'm planning on working on it this weekend, as we have a trip to Ocean Isle Beach NC coming up in May.

roadrunner · Post by **roadrunner** » Thu Mar 27, 2008 5:09 pm

PATRICKH wrote:Yeah roadrunner I have a good pedal too, except for when I get it on rough roads or off road. So flushing didn't work ??
I am kind of agreeing with horsehammerr in wondering if something electrical is to blame. A loose ABS sensor??? (think henryj mentioned this above) I'm planning on working on it this weekend, as we have a trip to Ocean Isle Beach NC coming up in May.

Nope, flushing did nothing for the problem. The best description I can give of the situation is this: It is just like when you have done a disc brake job and the first stroke or two (or more) the pedal will go clear to the floor until the pads are "traveled" back to contact with the rotors. When the pedal is thus "pumped back up" the brakes are working just fine. There are no warnings or lights on on the dash to indicate any electrical problems and if on loose gravel or mud or ice/snow the ABS system functions normally after pedal is restored. No indicators or lights indicate any brake problems and GM scanner check shows no codes or problems either. Patrick: let me know if you find anything in your search of your system. I'll keep everybody informed if I make any progress or "discoveries". Sorry to hear you're having this vexing problem as well. Perhaps the start of more troubles for everyone? Hope not!

Hey, hammer I appreciate the concern but don't loose sleep on this one. As with all mechanical problems it's just a matter of time till I get my "teeth" into this one and figure out the solution.
Again thanks to all for all help and suggestions they are appreciated.

roadrunner · Post by **roadrunner** » Sat Oct 25, 2008 1:17 am

10/25/08 Update: After reading the post on ZR2 forum linked from my brake wear problem post I shortened the booster rod 1/64th of an inch. The rod appeared to have sufficient clearance but I did this as a precaution and an experiment. I also installed 1" rear wheel spacers and home-built mud flaps. I don't think the flaps or spacers had any effect on this problem as they were aimed more at the premature wear problem but the rod shortening seems to have. I have not had this loss of pedal situation since working over the booster rod. YIPPEE!!!!!!!!!!! I intentionally waited this long to make sure the problem didn't recur or disappear due to coincidence. Again thanks to all for all suggestions and especially for the ZR2 link which started me to experimenting on the booster rod. Nice to have more dependable brakes again.

Rockrz · Post by **Rockrz** » Sun Nov 02, 2008 11:19 pm

Also, make sure your rear drum brakes are adjusted properly...if you have 'em

Horsehammerr · Post by **Horsehammerr** » Mon Nov 03, 2008 1:09 am

All Crew Cabs have rear inner drum brakes inside the rear disc rotor. Its the Parking Brake and only works when properly adjusted and released Before Driving. Don't even think about it as an emergency brake. Not going to happen.

roadrunner · Post by **roadrunner** » Mon Nov 03, 2008 9:19 pm

Ditto what hammerr said. 4 wheel disc ABS on the CC.