Mushy brake pedal

[camperguynj]

Mushy pedal is still an open item

Any thoughts or opinions on this diagnosis? Considering, I know nothing on this subject ... but can bore you on many others ... I would welcome your thoughts.

[Slantsixness]

Sent: 6/7/2007 5:22 AM

Mushy pedal sometimes, Hard pedal sometimes?

Assuming all of this is in proper operating order (no leaky wheel cylinders, master cylinder not leaking, Vacuum hoses to the boosters are not leaking, Boosters are at the correct pressures....)

1.  Bleed the brakes (again) Sometimes it takes more than twice to get all the air out.
and specifically, bleed the master cylinder to the Boosters, then bleed the brakes out. Air in the line between the Master and boosters will cause your symptoms too.

2. Adjust the brakes. your automatic adjusters might not be working as fast as you'd like them to. (besides, we usually back up in the motorhome fairly rarely, and only a few feet into a camping spot when we do. After de-glazing the shoes, the adjustment should be out at least a few clicks on the star wheel.

Warning:
Drum brakes can be subject to "brake fade". If the brakes are overheating, not only will the pedal "feel" change but it will also cause the shoes to overheat and "Glaze" again. And the motorhome will also take 2X as much distance to stop!
If brake fading is the case, and you're driving the winnie through  Mountains and steep grades, then slow down and use a lower gear (second in most cases) when descending the grade, rather than riding the brake pedal. (And I do think you're smarter than that Jim, but in general... some people have never seen or heard of drum brakes all around, so they would not know how to deal with it when it happened...)

For the most part, if the brakes are adjusted too tight, they will overheat and fade and your pedal will be mushy, then once they are superheated, the pedal becomes hard...(and stopping becomes even harder!)

If they are adjusted too loose, then the mushy pedal could be simply the extra amount of movement needed to apply the brakes. if you pump the pedal, and it becomes hard and raises, this is what is happening.


Ok....I think I've been on the soap box long enough...

Tom

[camperguynj]

Sent: 6/11/2007 1:33 PM

OK ... back from the weekend and road testing after abraiding (sp?) the pads and . Results? .... the howl/squeal has subsided but is still there.

Signed,
Frustrated

[Slantsixness]

Sent: 6/11/2007 7:22 PM

Jim or should I say "Frustrated",

The pedal being mushy on first application can be two things (although the two things can lead to procedures that have more than two steps)

1. Rear brakes incorrectly adjusted, or brake hardware (retainer springs) improperly installed, or an improper Master cylinder input shaft length
2. Air in the lines, slow leak, air not bled between the master cylinder and the Vacuum boosters.

Keep in mind:
if you have 4 rear wheel cylinders (2 per side) instead of just two, you can't bleed them like most braking systems.. but I do think you only have 1 per side... so look for some air in the brake lines, the rear brake shoe hardware or a rear brake adjustment, and see if that doesn't make you smile.

Tom

[ClydesdaleKevin]

Sent: 6/14/2007 10:16 AM

CamperguyNJ,

It definately sounds like you still have air in the lines.  There are some very good threads on the message boards about how to bleed your brakes.

A quick mini-explanation follows:

Start at the Vacumm boosters.  Do the rear one first, and then the second.  The do the farthest rear wheel (passengers side), both if you have 2 per side, then the drivers rear wheel.  Then the passenger's front wheel, then the driver's front wheel.

To do it by hand, get your brake bleeder hose and valve (don't use just a hose and a jar of brake fluid...get the little valve they sell cheap at NAPA.)  Now, if you don't have a trap door over your brake master cylinder where it can be seen from the inside, then this is going to be a 3 man job.  One to pump the brakes, one to keep filling the MC, and one to crack open the bleeders and then close them when the air is gone.  Okay...so all men are in place (if you do have a trap door, then the man pumping the brakes can keep the MC full)...now, with the wrench on the bleeder and the hose in place, call out "DOWN!"...the man at the pedal pumps it to the floor hard...you loosen the screw, he holds the pedal DOWN...when fluid stops flowing, you tighten the bleeder and call out "UP!"...the pedal man releases the pedal.  Now, keep repeating this until all air is out of the lines...it can take a very long time!

You can save a LOT of time and aggrivation by buying or renting a mechanical bleeder!  This is a hand pumped thingy, looks kind of like a grease gun, and it evacuates ALL the air out of the lines...you hook it up and pump away!  Now it really IS just a 2 man job...one keeps the MC totally topped off, while the other goes to each bleeder in order, and pumps away until the fluid runs clear and bubble free!  It works fast, although be prepared to go through almost a gallon of brake fluid!

I tried the manual pumping method when I did the brakes on the Ark, and while it worked, sort of, I still had the same mushy pedal problems you did.

Once I got frustrated and bought the bleeder (about 80 bucks) the brakes were right at the top, rock hard, and the Ark would stop on a dime!...well, it would stop quick for an old 72 25 foot long RV!  By the time the Ark was done, it was braking just as well as our Itasca, which has 4 wheel disk, and the Ark was 4 wheel drums!

One last thing to look for, and it was another reason we couldn't get the brakes to bleed right:

The wheel cylinders right and left (and top and bottom if you have 2 cylinders per wheel) are mirror images of each other, but are interchangable with each other...in other words, they'll FIT in the wrong places, and will even work, BUT your bleeders will be on the BOTTOM of the cylinder, instead of the top!  When I did the rear brakes on the Ark, some PO had put the old wheel cylinders on wrong...I didn't know any better, and put the new ones on the same way, leaving the bleeders on the bottom of the cylinder, with the brake line coming in at the top.  Until I took it all apart again and put them all rightsideup, I simply could NOT get that one last air bubble out of the rear cylinders, even with the mechanical bleeder.

So, a recap: 

Bleed the vaumm boosters first, rear first, then front! 

Then the rear passengers, rear drivers, front passengers, then the front drivers, in that order! 

Have your helper pump DOWN and hold the pedal down while you open the bleeder, and then release the pedal AFTER you close the bleeder.

You'll save yourself a lot of time and grief by buying or renting an handpump bleeder kit.  (And no one will have to pump the pedal!)

Finally, check to make sure ALL your bleeder screws are on TOP of every wheel cylinder, while the brake line should enter at the BOTTOM of each wheel cylinder.

Good luck!

Kev, Patti, the Furry Kids, and Excalibur!

[camperguynj]

Sent: 6/15/2007 7:52 AM

Once again you guys are amazing! Thanks for the "get-down-to-it" advice. From a guy who is just learning to crawl under this BIG plywood box your descriptions are clear while being detailed ... and being so new to this it's the little things like ... "go buy a bleeder hose "... "look for the bleeder valve at the top" along with the diagnosis and what to search for in trouble shooting the problem.

I purposely stayed away from the mechanic this week as I didn't want to ruin a good relationship because of my frustration. With Kevin's post along with the Tom's, Lefty's, Enigma, Jupp -- I feel confident that I can communicate a whole lot more intelligently with the mechanic and most important - now tackle this problem my self - with the help of a few friends.

Thanks Guys!! I will keep you posted

[camperguynj]

Sent: 6/20/2007 12:56 PM

This morning, armed with all of your information - I was down at the shop trouble shooting and learning how to bleed brakes. We started with the donuts, then moved on to:
* Pedal Pressure and return
* Master Cylinder input shaft
* Bleeders and lines for proper connection and leaks
* Bleeding the lines

Results -- both good and bad

Pedal return spring was hooked up incorrectly and changed to the proper hole. 100% difference ... Yes, being very cautious about applying and riding brakes (never did before ... but overly cautious now)

Tomorrow it is back down to the shop and we are going to take a look at the drums since there are no cracks, the shoes were chamfered as Jupp mentioned keeping our fingers crossed that now that the pedal (and spring ) has been set correctly that just roughing up the shoes one more time should do the trick.

- Jim.

[camperguynj]

Sent: 6/22/2007 6:35 AM

Finale:

Pedal mush fixed through re-bleeding lines and hooking spring to proper location 

Thanks for all the input and help ... the education and advice I received was put to good use and ... well ... as the commercial sez ... priceless.
- Jim

[007]

yup... throw it out there and you shall receive a wealth of input ,alot of really smart people here. IMOP