Brake pedal goes soft

[toddslater]

I did a quick search of the archive...didn't see this exact issue. Could be buried in one of those "descriptive" titles like "WTF???" or "need help".....Anyway, on to the show. Wife reports that when leaving school today, during backing out of the space, the pedal goes soft and heads to the floor. Pumped it and things seemed OK. Further down the road..at a light in town, she notices the pedal goes soft and can be pushed down without too much difficulty. So, I get home a little while ago ....fluid level OK, so out for a test spin. Only thing I notice is at a stop I can push the pedal downward with medium pressure. So, it is nearing dinner time and the little heater is on in the garage. I plan to check the usual suspects like a leaking caliper, line, and MC, but was also wondering about this......Today was the first freezing ass cold day here in the Philly area, and I'm wondering could this extreme temp change (it's prob still 50 deg in the garage this AM before she left outside is in the teens or lower) equate into either some air and or air/water trapped in the line causing the pedal to go spongy ? Your thought on this WAG theory. I'll check back after dinner.

 

[Scamper]

One (and maybe most likely) obvious culprit is the MC. But I'd also check the flexible brake line hoses at each wheel--if you've got a bad spot on one, it can expand as you press the pedal, then go back to normal when you let the pressure off.

I don't think it's air in the line since you'd see that every time, not just now and then.

 

[cruiserdan]

Loose wheel bearings. The rocking rotor pushes the pads back into the caliper and the first push on the pedal gets them back out against the rotor. The second pedal application feels right. As soon as you start going again the flopping rotor pushes the pads back in all over again.

 

[toddslater]

I'm headed down to the garage and will look real close at the hoses and I'll put it up in the air to and see if I can get some bearing movement....would have thought the latter would be noticeable while driving it. When I drove it I pumped a few times at the stop sign and then applied moderate pressure. It slowly gave way under moderate pressure. Two weeks ago replaced all 4 rubber hoses and rear cylinders in the 62. Last night, after buttoning up the HT install on the 40 nearly s*** myself under braking...right turn clyde. Fortunately had some rebuild kits on the shelf as the left front cyl's were both leaking. Ima getting tired of the smell of brake fluid. s*** happens in 3's. Must be true.

 

[toddslater]

Well, hoses are all OK, and the only lateral wheel bearing movement is miniscule in the front. The booster passed it's engine off and engine on tests. I am having a hard time going to the MC because it looks almost brand new. I have only had the truck for @ 3 months....and that MC looking as new as it does....I think I am going to bleed the system and see whats what. I know a pic doesn't help but this MC looks brand spankin new to me.
Any other thoughts....

 

[Gumby]

Does the pedal sink under constant pressure? If so, it's a leak, or if no fluid has gone missing, it's a MC.

If it goes soft while you are driving and sinks upon initial application, it could be wheel bearings, warped rotor or possibly bad hoses.

It's possible to get ice in the lines if the fluid is so bad it can no longer absorb the water. It sure wouldn't look like the fluid in the pics though.

 

[toddslater]

Yep it is a slow sink under moderate pressure...no fluid gone missing. No peddle pulsation like you'd get with a warped rotor. Maybe this frigid weather that just hit us was enought to send the little rubber piston/cyl cups into a thermal contraction to let some fluid pass. Hard to believe looking at the exterior. I'll give it a thorough blood letting in a couple days when I'm off and I can enlist one of my children to pump the pedal for me. I have one of those mighty vac hand pump thingies...but I'm not convinced it's all that wonderous. Time to watch a little football.

 

[Junk]

I'm thinking you have air in the system somewhere and would bleed it first, thoroughly, before I'd go MC.

 

[Docmallory]

I'll give it a thorough blood letting in a couple days when I'm off and I can enlist one of my children to pump the pedal for me. I have one of those mighty vac hand pump thingies...but I'm not convinced it's all that wonderous.

Have your kids buy you a Motive Power Bleeder for Christmas. You'll all be much happier. (Unlike the Mighty Vac, it actually works.)

 

[toddslater]

Hmmmm, the Mighty vac sucks and the Motive Power Bleeder Blows. Where have I heard that before ??? Anything else out there that people use that is better than the Motive ? This go around I'll do some bonding with the childrens and I'll do some search/comparisons of systems. Thanks Docmallory for the Motive Tip, may end up with one if nothing any better turns up at a reasonable cost.

 

[basalt51]

That "new" looking MC may be a rebuilt MC and many rebuilt MCs fail soon after installation since they have usually been bored out slightly.

FYI

Also, motive was offering free shipping last week so it might be a good time to get one

EDIT: free shipping here

 

[Texus]

bleedin'

Todd... pm snowcruiser... he's a buddy of mine & we bled mine, but can't remeber the brand... it worked so nice & we were done in less than a hour...we flushed out all the old...

 

[Arya Ebrahimi]

No personal experience, but I've been told "speed bleeders" are the thing to get. They replace the stock bleeder valves in the calipers and have one-way check valves in them. Once you open the valve you can pump to your hearts content. Air/fluid will escape the system, but not return because of the check valve. I plan to pick some up before I do my next brake job, which should be a while, since I just did a complete job on Saturday LOL.

Ary

Edit, the speed bleeders once installed, are left installed. This is not a "tool" per say that you use on different vehicles, but something you install and leave in place.

 

[toddslater]

but if i am reading you right, you do not love it. Can you say why just out of our curiosity? Thanks.

Naw I was just making the proverbial this sucks that blows joke up there. I have not used the Motive Products Bleeder...price is cheap enough and I like the theory of operation better than the "sucker". I am just going to look, ask, inquire with others on what they have purchased off the shelf and used. The only initial knock I have re: the Motive and its just on the face of it, is that it's basically a plastic bug sprayer with an adaptor and a pressure gauge. I already have the POS Mighty vac....so I'm just wondering what is out there in maybe the $100-$150 range that may be a little more robust.

 

[Gumby]

I'm pretty fond of the gravity bleed and then the two person bleed system. It has not failed me. Versus the other gadgets that have repeatedly. i want to know if there is a problem with bleeding that it is the system and not the tools.

 

[mytlc]

Being a Honda tech I must flush a least one or two brake systems every day at work, I use a 'Vacula' air powered vacume. Works excelent, just turn a new bottle of dot 3 upside down in the master resiviour to ensure you have enough fluid to flush with and start flushing one corner at a time. All 15 other techs in my shop use the same type of thing (maybee different brands, but the same design) and have never seen a problem, guess if your used to a tool it's easier to use then a once ever 24 month or so type thing. Just my 2 cents.

 

[Arya Ebrahimi]

No offense taken guys. There was a reason I prefaced my whole post with "no personal experience"

Glad to know they suck so I won't buy them. I have always used the gravity method as well, and it has always worked for me...

Ary

 

[toddslater]

mytlc,

Thanks for the post on the Vacula. I googled it and was looking at it and some other similar units from various parts houses...especially the ones that look like a little R2D2 units from star wars that start @ $200. While looking at the hits I ran across this one http://www.imperialclub.com/Repair/Brakes/bleeding.htm

I read through the first couple of posts on it and laughed a bit at the Mighty Vac sucks posts...laughing at myself mostly...then I remembered why I was there. So I did a "find on this page" thing and it brought me down the page to the guy who stared out using his Vacula, went on to the traditional wife approach, and then ended up with what appears to be one of these R2D2 type units.

This whole post may turn into a what bleeder do you use ? poll or some damn thing like that.