Turn Full Lock Left--> Brake Pedal Sinks To Floor

Livingcanvas · November 12, 2009

2001 ecsb 2wd 6" rancho lift, 35's

Ok guys I have a weird brake issue. Whenever I turn full lock, or close to it, to the left, when I go to hit the brakes after that they sink all the way to the floor, with barely any braking power. I have to pump them up about three times to get my brakes back. Only does this to the left, not to the right. This has nearly caused me to crash a couple times now.

I've gone over all the lines and abs sensor wires and everything looks fine

What the hell could it be? Please help

Matt_ · November 12, 2009

If you turn the wheel full left while not moving, does the pedal go do the floor?

It's likely that one of your brake hoses are failing. When pressure increases a section of it will blow up like a balloon.... depending on how the hose is kinked when turned right, it may not be expanding and therefore you have brake pressure. Then when you turn the other way, it's in a different position and expands.

If the pedal goes to the floor when the wheel is turned with the truck in park, have someone hold the pedal down while you inspect the lines for any bulges; DONT DO THIS IF THE TRUCK IS NOT IN PARK!!!!

First thing I would do before driving again is to replace both front brake hoses and bleed the system really good. Make sure you bleed all 4 corners.

Stevens03 · November 12, 2009

Welcome to the site, but the obvious question I have is WHY THE HELL ARE YOU DRIVING IT LIKE THAT?!?!?!

Before you hurt yourself or some one else, you need to fix it. I know thats what your trying to do now... but I would not drive it until it's fixed.

Nytemare · November 12, 2009

+1 to all of the above.

gmtech4 · November 12, 2009

this start after the lift?

minibike132 · November 12, 2009

Unwanted abs activation on this truck feels the same as what you are talking about. I would almost put money down that if you had the proper scanner you could see one of the sensors dropping out and the dump valves kicking at one or more wheels.

My vote is put front sensors in it and call it a day, that is provided there is no slop in any of the bearings.

Livingcanvas · November 13, 2009

Ok wow first, thank you guys for the quality of answers.

I doubt a ballooned line because it doesn't only happen during the turn. For instance, I can pull a U turn no brakes, drive down the street then at the end of the block when I go to brake, it happens.

I bought the truck already lifted.

I think the front sensors suggestion makes the most sense at this point. On these truck aren't the abs sensors part of the hub? Or can I buy just sensors? The only problem I have with this suggestion is the when it happens, I do not hear the abs motor, nor do I feel it. It just sinks down as if I opened a bleeder. Btw, fluid level is unchanged

One note. The truck has the abs and brake lights on in the dash because of the 35s as the truck has not been tuned for them. They only come on randomly and this problem happens regardless of them lit. Also, if they are not lit when it happens, this does not cause them to light up.

Should I have it scanned with a tech2?

Matt_ · November 13, 2009

I doubt a ballooned line because it doesn't only happen during the turn. For instance, I can pull a U turn no brakes, drive down the street then at the end of the block when I go to brake, it happens.

Why do you doubt it's a ballooned brake like again? Those are all symptoms of a failing brake line. As a matter of fact, since you say it happens more than just turning left then it makes it all that much more of a possibility.

Can you make the pedal go to the floor with the truck in park? If you can, have someone hold it there and check the lines.

minibike132 · November 13, 2009

Ok wow first, thank you guys for the quality of answers.

I doubt a ballooned line because it doesn't only happen during the turn. For instance, I can pull a U turn no brakes, drive down the street then at the end of the block when I go to brake, it happens.

I bought the truck already lifted.

I think the front sensors suggestion makes the most sense at this point. On these truck aren't the abs sensors part of the hub? Or can I buy just sensors? You can get just the sensors, if you decide to replace them make sure the mounting surface is COMPLETELY free of rust and debris. Also make sure there is no play in the hub before doing just the sensors. The only problem I have with this suggestion is the when it happens, I do not hear the abs motor, nor do I feel it. You often cannot hear or feel it when it happens with trucks, it just feels like it sinks. It just sinks down as if I opened a bleeder. Btw, fluid level is unchanged

One note. The truck has the abs and brake lights on in the dash because of the 35s as the truck has not been tuned for them. They only come on randomly and this problem happens regardless of them lit. Also, if they are not lit when it happens, this does not cause them to light up. The light never comes on when the sensor causes this problem. The reason is that it only sees a glitch where the sensor drops out from a slow speed for a second. To the computer that looks like a wheel locked up and means it is time for activation. To the computer it doesn't indicate an issue with the sensor, it indicates a wheel stopped turning. If it happened at higher speeds it would cause a light.

Should I have it scanned with a tech2? Scanning it alone will tell you nothing, there is almost never a code associated with this for the reason I just stated. A tech with a little experience would watch the wheel speed sensor data to see if one drops out when the problem occours. A good tech would watch the abs pump for activation and which wheels dump when it does activate.

It may or may not be a sensor but I'm going with most likely suspects here. I think I've replaced 1 line for ballooning in the last 5 years and it was never felt in the pedal, only found during an inspection. I have replaced hundreds and hundreds of hubs and or sensors for what you are describing. If it were in my bay I wouldn't go indicrimately replacing sensors, it would get the diagnosis I described first. Weather there was unwanted activation or not a full visual inspection would be included with the diagnosis. Don't go replacing anything just on my say so, most shops are going to charge about an hour to do what I would do with the scanner and the visual inspections, it's your brakes do it right.

minibike132 · November 13, 2009

I doubt a ballooned line because it doesn't only happen during the turn. For instance, I can pull a U turn no brakes, drive down the street then at the end of the block when I go to brake, it happens.

Why do you doubt it's a ballooned brake like again? Those are all symptoms of a failing brake line. As a matter of fact, since you say it happens more than just turning left then it makes it all that much more of a possibility.

Can you make the pedal go to the floor with the truck in park? If you can, have someone hold it there and check the lines.

If you can make it go to the floor in park check everything hydraulic. If you can't make the pedal drop at all then you can just about forget anything hydraulic.

Matt_ · November 13, 2009

exactly. we're on limited info here... so might as well start with the basics. If he can make the pedal go to the floor while not moving, then ABS is also out of the question.

Edit: and on the other hand, if the pedal won't go to the floor without the truck moving and no matter how the wheel is turned, then its probably not in the lines and has to do with the ABS. Basically just a quick "at home" check to segregate the potential cause without throwing parts at it. From there he can more easily decide whether he wants to change sensors/lines/etc. and will have a better chance of success.

Livingcanvas · November 13, 2009

Ok today I tried it in park and it does not happen when the truck isnt moving. Plus like I said, when it happens, I have to pump the pedal to get brakes back. Which also leads me to believe that the abs is dumping on me.

Again, thanks for the quality of answers. I am definately not the type to throw parts at it and see what sticks, so thanks for the replies

BTW I do all my own work on my vehicles. I used to be a mechanic at a performance shop that dealt with late model GM stuff like LS1 Camaros and Corvettes and such. So, I am a competent parts changer, but not so great and certain types of diagnostics, especially something like ABS action on lifted trucks. Im mostly an engine guy. So, again, thanks for the info fellas

man00 · November 29, 2009

exactly. we're on limited info here... so might as well start with the basics. If he can make the pedal go to the floor while not moving, then ABS is also out of the question.

Edit: and on the other hand, if the pedal won't go to the floor without the truck moving and no matter how the wheel is turned, then its probably not in the lines and has to do with the ABS. Basically just a quick "at home" check to segregate the potential cause without throwing parts at it. From there he can more easily decide whether he wants to change sensors/lines/etc. and will have a better chance of success.

I wasn't aware you could change just the front sensors, I thought you had to buy complete hub assy ?

If you can buy the sensors..show me where

thansk

bossier62guy · November 29, 2009

exactly. we're on limited info here... so might as well start with the basics. If he can make the pedal go to the floor while not moving, then ABS is also out of the question.

Edit: and on the other hand, if the pedal won't go to the floor without the truck moving and no matter how the wheel is turned, then its probably not in the lines and has to do with the ABS. Basically just a quick "at home" check to segregate the potential cause without throwing parts at it. From there he can more easily decide whether he wants to change sensors/lines/etc. and will have a better chance of success.

I wasn't aware you could change just the front sensors, I thought you had to buy complete hub assy ?

If you can buy the sensors..show me where

thansk

www.rockauto.com for one.....

minibike132 · November 29, 2009

exactly. we're on limited info here... so might as well start with the basics. If he can make the pedal go to the floor while not moving, then ABS is also out of the question.

Edit: and on the other hand, if the pedal won't go to the floor without the truck moving and no matter how the wheel is turned, then its probably not in the lines and has to do with the ABS. Basically just a quick "at home" check to segregate the potential cause without throwing parts at it. From there he can more easily decide whether he wants to change sensors/lines/etc. and will have a better chance of success.

I wasn't aware you could change just the front sensors, I thought you had to buy complete hub assy ?

If you can buy the sensors..show me where

thansk

www.rockauto.com for one.....

www.gmpartsdirect.com

any dealer

nappa

carquest