You guys ever have this happen?

I was climbing a stump yesterday. Front was way up. I put it in park, turned off the engine and climbed down to see if my anti wrap link bar was twisting like it was supposed to and was not limiting my droop.

I had just a heim joint threaded into a single nut welded to the end of the link bar, but there was enough slack in the threads that it would flex through the threads and give me a bit of a clunk every time I changed speed. To remedy it, Rick W welded a short stub of Sch 40 to the existing bar/nut link with another nut on the end of that. So, the heim thread is now in double shear with a 1 1/4" spacer between the nuts. No more rocking in the threads.

But, of course, welding it changed the dimensions of the metal, so it jams the heim threads a little. It can be turned by hand, but takes a lot of effort. It should loosen up with time. I greased up the threads when I put it on the truck. But, it is hard to tell how well/much the threads are turning. The axle was at a significant angle to the bumper/crossmember, but I was in dirt and not work clothes so I did not want to crawl under there. What I will do tonight is paint a thin white line across the side from the nut across the threads, that way I can eyeball the line displacement to see how much the bar is rotating on the threads...

But, back to my story.


Climbed back in, fired it up, put my foot on the brake, put it in reverse to back off the stump, started to roll, and the brake pedal suddenly went to the floor, needless to say I came off the stump at a fast clip. I threw it into neutral on the way down, and pumped the brakes. Came to a stop right after I levelled out. Pumped the brake a couple more tiimes, nothing. Put it in park and turned it off. Climbed out, figuring I had ripped a line or something, no brake fluid anywhere, climbed in, started it up, normal brakes. Drove home, drove to work, normal brakes.
Any ideas on this one?

Pretty sure I have the fronts bled pretty well. three reservoir worth out each side, no air bubbles at all, never ran the reservoir dry....
Back might have a little air, haven't bled them since I did the rear soa. My brakes are a little spongy, compared to the saturn or van, but I can still easily lock up front and rear, without a lot of pressure, and long before the floorboards....

Only thing I can figure is that I had a big air pocket somewhere that floated to the surface when I was at the angle.
But, don't know where it went once I was back on level ground...?
Very odd.

Not taking it to a brake shop. They will make me replace everything that does not need to be replaced and charge me $800 I don't have...

I'm just talkin out of my ass here, but I would be huntin a new master cylinder.

Originally posted by Hayraker
I'm just talkin out of my ass here, but I would be huntin a new master cylinder.


Hmmm. OK. I'll bite. How would a bad MC cause this. Not saying yeah or nay. Just looking to understand...

Gonna do some more testing, also, over the next couple days. See if I can get it to do it again...

Thanks.

Is there a chance that with the angle that you were at on the stump, all the fluid moved away from the plunger? It should have allowed air into the rest of the system but it might be possible that it didn't.

Originally posted by HarleyM
Is there a chance that with the angle that you were at on the stump, all the fluid moved away from the plunger? It should have allowed air into the rest of the system but it might be possible that it didn't.

Anything is possible.

Can't figure out how ANY air could have gotten into the system, and since the sytem is full of fluid, there is no room for the fluid to get away from the plunger. At least, none that I can see. The reservoirs were full. If there was any air, it was minimal. Even standing on my tail, the air could not have gotten down by the lines, or plunger.

Drove it around at lunch today, no hiccups, etc. Braked just fine...

Could a pinched line perhaps cause this? Maybe I pinched something? Or, maybe I sucked some air somehow, but it seems like I should be really spongy if I had air, and the brakes feel the same now as they did before my *incident*.

It is very odd. Thanks for the suggestion though. I'll see if there is any way that could have happened.

Pedal to the floorboards. Pumping the brakes did not help at all. Very odd.

hmmm

maybe just maybe the front reservoir draned into the rear reservoir juse enught that the front fluied port was open to the air so it pumped air into the sysem

just a thought

I'll vote with Harley on this one.

'shooting from the hip hid behind my computer like a little kid'

wp

Off chance it could be a bad wheel bearing. When you pulled up on the stump the bad bearing could have let the wheel hub tip the rotor away from the piston in the calliper. Then when you hit the brake the piston had to move much further to take up the slack.
OK it's just a guess but nothing else makes sence either.:)

my vote is with scoutaholic on this one,check the frontend for anything that could have forced the piston on the caliper back.
i guess balljoints and bearing is about all you can check....my .02

Originally posted by Hooper
You guys ever have this happen?.....the brake pedal suddenly went to the floor...
:D :D Your screwed.:D :D

Originally posted by Scoutaholic
Off chance it could be a bad wheel bearing. When you pulled up on the stump the bad bearing could have let the wheel hub tip the rotor away from the piston in the calliper. Then when you hit the brake the piston had to move much further to take up the slack.
OK it's just a guess but nothing else makes sence either.:)

That is a distinct possibility. But, I jacked the front end up and the front bearings are tight.

However, I think this is the right track. I think for some reason the piston had to travel way too far. Maybe it was in crooked or something and it straightened out, which left it slack from the last time the caliper extended? Have to look into that.

I am thinking it is not bearing problems, but, something.

good ideas. Thanks

Originally posted by Snoopy

:D :D Your screwed.:D :D

Yeah, great. You are a lot of help!!! ;)

Hooper, did you figure out your brake problem?

Originally posted by HarleyM
Hooper, did you figure out your brake problem?

Nope. Bled em all the way around. No air at all. Brand new hoses all the way around also. Bearings are tight, no play in the wheels. Pads and calipers are tight.

No idea at all. Wierder than wierd. But then, it has not done it again, either.

I am going back to the same tree stump tonight. See how it reacts this time...

I'd Replace the Master Cylinder asap.............
Theyre cheap and your life isnt worth the risk......
:beer:

Originally posted by The Chad
I'd Replace the Master Cylinder asap.............
Theyre cheap and your life isnt worth the risk......
:beer:


ahem........... I agree, (I think I said this in the first reply)

Next time it happens you might be on flat ground, climbing that stump could have been a coincidence.

Originally posted by Hayraker



ahem........... I agree, (I think I said this in the first reply)

Next time it happens you might be on flat ground, climbing that stump could have been a coincidence.

Hmmm. All right. I I will go buy a new MC and slap it in.

This is a classic symptom of a failed M/C. You guys should know that. duh. :flipoff2:

Originally posted by Hammerlock
This is a classic symptom of a failed M/C. You guys should know that. duh. :flipoff2:

Really? Know anyone who has had this symptom? A couple of you suggested this might be the problem, and it is cheap insurance to replace the MC, but no one has come forward and said that they KNEW the MC was the problem and that the reason they knew it was the problem was because XYZ. All I have really heard was, better change the MC because that might be it, it is cheap and easy to replace, and better safe than sorry. Those are all valid points, but none of those explain to me how it is that I should recognize this as a *classic* symptom of a failed MC, nor has anyone explained to me why this would occur mechanically.

So, since this a classic symptom, can you explain to me what happened and why?

:D

Originally posted by Hooper


Really? Know anyone who has had this symptom? A couple of you suggested this might be the problem, and it is cheap insurance to replace the MC, but no one has come forward and said that they KNEW the MC was the problem and that the reason they knew it was the problem was because XYZ. All I have really heard was, better change the MC because that might be it, it is cheap and easy to replace, and better safe than sorry. Those are all valid points, but none of those explain to me how it is that I should recognize this as a *classic* symptom of a failed MC, nor has anyone explained to me why this would occur mechanically.

So, since this a classic symptom, can you explain to me what happened and why?

:D

Your M/C didn't pump the hyd. fluid because it's a POS. Don't drive it until you get it fixed.

(I'm assuming you keep the M/C topped off)

Originally posted by Hammerlock


Your M/C didn't pump the hyd. fluid because it's a POS. Don't drive it until you get it fixed.

(I'm assuming you keep the M/C topped off)

Ahh, a very technical answer. I am much better enlightened now!!! :D

Yep. MC is full to the brim. I had just bled the brakes a few days prior, and I checked the level once I got to flat ground. As you say, for some reason the MC did not pump the fluid... I was thinking a pinched line, or collapsed line or something along those lines, but i will start with the MC. It is three years old anyway..

Originally posted by Hooper


Really? Know anyone who has had this symptom? A couple of you suggested this might be the problem, and it is cheap insurance to replace the MC, but no one has come forward and said that they KNEW the MC was the problem and that the reason they knew it was the problem was because XYZ. All I have really heard was, better change the MC because that might be it, it is cheap and easy to replace, and better safe than sorry. Those are all valid points, but none of those explain to me how it is that I should recognize this as a *classic* symptom of a failed MC, nor has anyone explained to me why this would occur mechanically.

So, since this a classic symptom, can you explain to me what happened and why?

:D

Ive run into only 100 or so with this problem Hoop, Since I do brakes for a living...

Basically fluid is leaking past the MC piston, hence.. No pressure.............

Originally posted by The Chad


Ive run into only 100 or so with this problem Hoop, Since I do brakes for a living...

Basically fluid is leaking past the MC piston, hence.. No pressure.............

Yeah, and I have heard that it gets up against the booster diaphram and eats it away, also...

Yes it does!

I think Rick had the right idea. When you get it all twisted up with a wheel turned a bit, is it possible that the backside of the caliper touches a shock or ???? If so, that would push the piston back into the caliper which would take a couple pumps of the pedal to push back out. Look around under the truck and make sure that there's no shiny spot on the caliper where it may have touched some hard spot on the truck.

I'm just a lowly newbie, but I'd be looking for what Rick was talking about.

lowly newbie.... HA


hey Jason, send me a PM or an e-mail with your mailing addy..... I got something to send you.


I can't seem to find were I wrote your number....


-mark
marka@4x4play.com

Originally posted by Jason Lockwood
I think Rick had the right idea. When you get it all twisted up with a wheel turned a bit, is it possible that the backside of the caliper touches a shock or ???? If so, that would push the piston back into the caliper which would take a couple pumps of the pedal to push back out. Look around under the truck and make sure that there's no shiny spot on the caliper where it may have touched some hard spot on the truck.

I'm just a lowly newbie, but I'd be looking for what Rick was talking about.

Look at this brave soul, using his REAL name for his PBB moniker!!

Welcome Jason. I'll take a look for something the caliper could have hit.

I did check the bearings, they are in good shape...

Hey Hooper,

I was searching around checking out info on Residual Pressure Valves and came accross this website that stated this about 4wheel disk set ups:
"2 PSI Valves - These valves are used in a disc brake system only and are required when the master cylinder is at, or below, the height of the calipers. It's purpose is to act as an anti-siphon valve preventing the brake fluid from siphoning back into the master cylinder when the brake pedal is released. Even if the master cylinder is even or slightly above the calipers, put one in anyway. If you don't and you park on a hill, fluid will siphon! These valves are cheap insurance - put them in!
NOTE: You will know if you need one of these valves if you had to pump the pedal twice to get a good pedal. See illustration for more"

I realize that you still have rear drums, but I am thinking that maybe your system siphoned back? I dunno..here is the URL: http://www.ecihotrodbrakes.com/brake_facts.html

Originally posted by Scout Dude
Hey Hooper,

I was searching around checking out info on Residual Pressure Valves and came accross this website that stated this about 4wheel disk set ups:
"2 PSI Valves - These valves are used in a disc brake system only and are required when the master cylinder is at, or below, the height of the calipers. It's purpose is to act as an anti-siphon valve preventing the brake fluid from siphoning back into the master cylinder when the brake pedal is released. Even if the master cylinder is even or slightly above the calipers, put one in anyway. If you don't and you park on a hill, fluid will siphon! These valves are cheap insurance - put them in!
NOTE: You will know if you need one of these valves if you had to pump the pedal twice to get a good pedal. See illustration for more"

I realize that you still have rear drums, but I am thinking that maybe your system siphoned back? I dunno..here is the URL: http://www.ecihotrodbrakes.com/brake_facts.html

Now, that makes a lot of sense. I always assumed there was a check valve in there, but then you wouldn't be able to compress the caliper back down for new pads.

So, maybe I did get siphoning, which would be close to what rick and jason were saying, i.e. a caliper compressed (siphon instead of contact but same idea) and had to be pumped back out. Scoutillac had the same problem recently, after being parked on Caines tire for a few hours.... Bet that is it!!

good find! Thanks for the info.

So Hooper what was the outcome here?

I have a similar problem on my Jeep with dana 60 F/R Disks all around.
I suspect I might have a caliper that is getting pushed in on me and will inspect it tonight. Everything else is NEW on my set up (not rebuilt) and I too have no leaks or air in my lines.

Go up an incline and I loose the pedal. fawking weird!

Corvette MC, Jeep Booster, Stock Chev dana 60 single piston Calipers up front, 3/4 ton Chev calipers rear, Summit Prop Valve rear line and 2 lb residual valves F/R. (yes my plunger is adjusted properly, and I bench bled too)