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HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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bahop
Novice
Sep 16, 2010, 11:51 AM
Post #1 of 14
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HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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Brakes problem
1995 Plymouth Voyager 6 cyl Front Wheel Drive Automatic 150k miles
I posted this same ongoing problem last winter. U can read the thread here;
link deleted........ not allowed
basically I have had a SOFT pedal appear, disappear & reappear for over 9 mos. w/ NO visible discernible fluid loss
1 trip/1 day/1 week it's ALL firm & fine - the next trip /next day/ next week it's soft & the brake light comes on accompanied by a springy sounding click under the dash (which I assume is the pressure differential switch tripping?).
I have had 3 shops/mechanics assess it & heard 3 different opinions;
*shop#1 -says NO leaks -MC GOOD -booster BAD. problem w/ that is I have vacuum pressure & NO hard pedal, also checked for fluid in booster & found NONE. anyway -can a booster go out one day & not the next??? so that doesn't seem to fit.
I have talked w/ several independent mechanics & spent considerable time online in forums & researching the problem. as in my previous post the consensus seemed to be MC so I replaced w/ a rebuilt one & all was FIRM & fine for about a week & then the next morning it's gone again.
**shop#2 bleeds complete system (but not sure
ABS mod was opened). they say left rear wheel cylinder is leaking & should be replaced. Aha! this makes sense & is my answer...
hire independent (flaky CL) mechanic to replace it & he adamantly says NO leaky wheel cylinder. I contest & question that & he says shop#2 trying to 'rip me off' (& why he no longer works for shops). he says rebuilt MC bad & should be replaced w/ new one - so I do.
brakes are FIRM & fine for another week & then gone again one morning. I bleed that circuit (suspected wh cylinder) & still seems to be air in the line. once again all is FIRM & fine for a few days & then SOFT & brake light.
when it goes out, I can pump pedal a few times & light goes off & can get pressure back. sometimes it stays awhile, sometimes it's gone by the next brake stroke.
more data (& questions);
---temperature & atmospheric weather changes seem to trigger the change. can parts be expanding contracting w/ minimal seepage yet enuff to lower the hydraulic pressure?
--- my drive is a steep incline & I park w/ rear higher than front. could trapped air be working thro the lines at these changes in angle?
I've sunk quite a bit of time & money into this @!#$% problem already w/ NO resolution in site. I'm completely baffled & frustrated (& depressed) with it. I really don't know where to look next...
anyone HELP please??? would appreciate any theories -covered or not
thanx
bahop
(This post was edited by Hammer Time on Sep 16, 2010, 2:15 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 16, 2010, 3:48 PM
Post #2 of 14
(1826 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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bahop: Read that thread before it was removed. (we just can't allow links to other sites) Long thread and you got some VERY high end suggestions.
Know this - back brakes are chiefly responsible for pedal height but shouldn't be so intermittent. They really need to be perfect and perfectly adjusted with proper parking brake items. Don't count or "self adjustment" unless all hardware is new. The adjusters just tend to give up so you would manually make adjustments or toss all that stuff.
Only heard of it once! Of a couple wild maybes you may have air in system but I don't think that's the whole game. Could have a second bad MC too - stuff happens.
The one whacked problem seen just once was flex hose that could balloon out but didn't leak! You would have to witness it. Another whacked and dangerous problem is somewhere along the way someone put NON brake fluid in master cylinder. An oil with swell rubber parts and would eventually be a nightmare.
Never happened to anything I ever worked on but have good info that an oil would sit on top or brake fluid but not that it's been bled out it would be thru the system. Near sure you would see the rubber seal of MC bloating up if so. The fix if something like that happened would mean replacing everything in the brakes that use rubber! Would be nasty expensive,
T
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bahop
Novice
Sep 17, 2010, 3:33 PM
Post #3 of 14
(1807 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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thanx for the time.
I've had the whole system bled & no way anything BUT dot3 is in there.
I pulled the rear hub again & checked under the dust seals of the wheel cylinder in question. it IS moist but not too wet on each side. the guy who claimed it wasn't leaking said it was brake grease, but should it be there? I thot it should be DRY. at any rate, not a LEAK in my book, but if it were just a small seep??? wouldn't it be a full blown leak after 9 mos. of this??
anyway, BLED the lkine in question again & have a rock hard pedal like a shot of Viagra... just seemed like an AWFUL lot of air in there as I made at least 20X passes on it. each time air seemed gone, it would start to sputter again so I don't feel like I know if I ever really got it all or not. one theory I've heard is that the wheel cylinder is sucking air but resealing so the fluid doesn't leak out - kinda like a check valve. if it can do that? I theoretically could be bleeding it all day & never get it clean.
what say you? ever heard of that? as uncommon as it may seem?
thanx again. anything is appreciated...
bahop
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Hammer Time
Ultimate Carjunky
/ Moderator
Sep 17, 2010, 4:19 PM
Post #4 of 14
(1801 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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Brake grease inside the wheel cylinder??
What's he smoking?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 17, 2010, 5:00 PM
Post #5 of 14
(1797 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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Yes - rubber friendly brake grease is used in/on surfaces for both drum and disc brakes. Are you bleeding this with a helper? Is the drum on when you are bleeding them?
Helper needs to hold brake pedal down till no more fluid is coming out and NOT move foot till bleeder is shut again or you are just sucking air back in.
If there was a tad of grease on push pin at the wheel cylinders some folks will do that. It's easy to tell brake grease from brake fluid as the brake fluid will wash off in plain water - the grease won't.
Unless overhead on a lift you would likely bleed brakes with drums and rotors on and a few lug nuts to hold them tight. Wheel off but the parts all on.
Can a wheel cylinder plain suck in air? Not likely but there is residual pressure on wheel cylinders to hold the cups tight or they could plain leak.
Are back brakes all in order and adjusted properly? Once you start to get fluid it usually just takes a few more times and it's done. Has master cylinder been allowed to run dry while bleeding? If so you would need to start all over.
Is vehicle level while bleeding brakes? Was master cylinder bench bled? All this matters or you can do this all day and never get there. Have any brake lines been replaces and NOT places back exactly where they were? It a line is misrouted near hot exhaust the fluid inside could boil and you would lose your brake pedal if boiling.
T
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bahop
Novice
Sep 20, 2010, 6:27 AM
Post #6 of 14
(1774 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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YES, vehicle WAS level & drum & wheel has been on while BLED, (except maybe this last time) -wondering how both of those affects bleeding? & if so would it help to put rear wheel higher?
anyway, YES - MC was bench bled, & helper IS keeping foot down until line is closed again. NO brake lines replaced. substance under dust seals looks greasy but also liquidy so I'll try the water test next time I have wheel off.
like I mentioned, it just seems like the air doesn't end, & just when it's seems clear & it's all out for maybe 2-3 bleeds, it starts sputtering again w/ another round of bubbles for 2-3 bleeds, so it seems like it's just getting sucked right back in.
it was suggested that I got a 2nd bad MC (again) but that wouldn't put air in the system. I've noticed a lot of liquid around the MC caps even after I keep wiping up. I know it could be just spillage from all the reservoir filling but could they be bad???
anyway, STILL baffled, but so far still have FIRM pedal after last bleed. it hasn't been lasting more than a week & the weather also changed last nite, which also seems to affect it. any theory on atmospheric pressure changing brake pressure???
thanx
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re-tired
Veteran
/ Moderator
Sep 20, 2010, 4:51 PM
Post #9 of 14
(1752 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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A few thoughts on the subject . Have the rear brake adjusters been checked for being swapped lh to rh?If you can get to happen at home try this to narrow it down. Find the rubber flex hose to the rear axle ,they make a clamping tool or you can carefully use needle nose vise grips . .Clamp the hose at the end farthest from axle (TOP) see if prob goes away . If not try each front flex hose the same way then both front hoses together . Finally clamp off all three, if prob is still there undo lines at m/c and install plugs (avialble at some parts houses like napa). If it still does it . It has to be m/c , maybe cups flipping over .
LIFE'S SHORT GO FISH
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bahop
Novice
Sep 22, 2010, 3:25 PM
Post #10 of 14
(1726 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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OK I hear you. so far pedal holding (knock on wood) but it hasn't been a week yet & that has seemd to be the limit lately...
a bit more data... my front master cylinder cap is leaking- 1st I thot it was just spillage but it keeps coming back after wipe up. could that compromise a sealed system? not likely I'm thinking
but what about ABS?? could air get trapped in the modulator & then released when the system is used? I took to a 'brake chain shop ' to have the system BLED after replacing the MC the 1st time because the manual says my ABS needs a special tool to open the valve. I thought that's what they did but I found out afterward they didn't & I coulda saved myself 50 bux to do it myself. when I had/have soft pedal I'm able to pump it up for a stop or 2 & at times when doing this the left rear wheel (cylinder) in question has locked up & the only one to do so. ABS light never comes on & other wheels don't.
any creedence to this theory? or does it give rise to another??? or point even stronger to wheel cylinder?
thanx
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 22, 2010, 4:05 PM
Post #11 of 14
(1723 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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Already said about an oil and you said NO so I'll believe you. Know this. Even a little air when cold which is no doubt when you are bleeding brakes if still in there and just won't make it to burp out at the master will expand a lot depending on where it has managed to be.
Ex: Take an ordinary balloon and put in in your refrigerator and see how small it gets. Heat it up and it would get larger. That small temp changes. Brakes can get hot normally in use. Lines and items with engine heat is way up there too. A line near exhaust parts can exceed 300F!
Think I asked - Has any brake line(s) been replaced? If so they MUST be in the original location which is though of when original to be out of the way of hoisting the vehicle, hot parts and a fair attempt to have them out of harm's way from road debris.
The level in MC would change within range normally from stone cold to after run and brakes used but not spill over. That's why most are marked with a MAX level and bellows in sealing rubber caps.
Basics: When you apply brakes fluid moves out of MC to the wheel cyl. and calipers. Release brake and it returns.
I say there's still some air in there and depending on where if pedal feels good now may not for long??
T
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bahop
Novice
Sep 24, 2010, 7:23 AM
Post #12 of 14
(1698 views)
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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thanx,
this makes the most sense to me & I've always suspected it -as explains why pedal firmness comes & goes when the weather changed (atmospheric pressure & temp). one day brakes working firm & fine, then next morning after a weather front moves in it's gone. weather changes again & pedal is back again. does that seem possible & make any sense?
altho it doesn't explain how air got in my system to begin with, but that could really just been the bad MC & everything since I replaced it is just chasing down residual air...
based on this theory, would it be easier to BLEED line after driving & it's HOT -while air is expanded? I've been doing 1st thing in a.m. before starting up.
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Hammer Time
Ultimate Carjunky
/ Moderator
Sep 24, 2010, 7:26 AM
Post #13 of 14
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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No, atmopspheric pressure is not effecting your brake pedal.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 24, 2010, 9:55 AM
Post #14 of 14
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Re: HELP!!! BAFFLED (& FRUSTRATED) BY SOFT BRAKE PEDAL
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Not atmosphere as HT just said. Wild temps - yes. Pure DOT 3 is rated boiling point of 450F. If it boiled it would behave like air while in that state then contract.
Quote by bahop from first post">>disappear & reappear for over 9 mos<<"
Isn't it time to just have this professionally pressure bled? No air is the objective not just less.
This isn't worth re-inventing the wheel over vs just paying on the high side perhaps an hour's labor with the right shop that has the equipment.
Some vehicles are just fussy so let it go..........
T
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