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2003 chevy trailblazer_lt
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Discussion Starter · #1 ·
I need some help, I am experiencing a pretty irritating problem. My TB must be trying to tell me I'm going too fast.

A few days ago I noticed that the tranny had to down shift in order to maintain speed with the cruise on going down a hill. Today I felt like I was towing a freight train behind me. When I got out of my truck the front two brakes were smokin' hot literally. The brakes seem to be applying themselves. It is off and on and when they are on and I touch the brake pedal it is rock hard and almost neck snapping quick, not like it normally is with the mushy pedal.
 

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Could have air in your brake lines.. i would Bleed the brakes and top off the master cylinder. Check and see if you are low on Brake Fluid..
 

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2003 chevy trailblazer_lt
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Discussion Starter · #3 ·
plenty of fluid in the reservoir, the system was flushed, re-fillled, and bleed just over six months ago.

i did have the booster line off two weeks ago and ran some sea-foam thru it into the manifold, haven't driven it a lot since then, forgot all about that.
 

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plenty of fluid in the reservoir, the system was flushed, re-fillled, and bleed just over six months ago.

i did have the booster line off two weeks ago and ran some sea-foam thru it into the manifold, haven't driven it a lot since then, forgot all about that.
check for leaks at on the Booster line.. Get a spray bottle with Dishwashing Liquid and water and spray around the hose and see if it bubbles.. That would show Vac leaks..
 

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check for leaks at on the Booster line.. Get a spray bottle with Dishwashing Liquid and water and spray around the hose and see if it bubbles.. That would show Vac leaks..
ummm.... if its a vac line and you spray it with soapy water.... its just going to suck it in. that only works with lines under positive pressure. :m2:
 

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2004 gmc
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Could have air in your brake lines.. i would Bleed the brakes and top off the master cylinder. Check and see if you are low on Brake Fluid..
You're guessing. Air would make them soft.

check for leaks at on the Booster line.. Get a spray bottle with Dishwashing Liquid and water and spray around the hose and see if it bubbles.. That would show Vac leaks..
STOP GUESSING. YOU'RE NOT HELPING. A leaky booster would require more pedal effort. What he says is he gets braking action with ZERO pedal effort.

would a vacuum leak cause the symptoms i'm describing??
Of course not.
what make the brakes come on and stay on?
Bad piston seals not retracting the pads properly. Odd for it to happen on both sides at once. A problem with the ABS system could trap pressure and not release it. I'd pull the battery for a half hour to force an ABS reset, even if the Service ABS light isn't on. If that's not is, get to a dealer who can talk to the ABS module with their tech tool. You could boil your fluid, which may be aggravating your problem by building excess pressure which boils the fluid harder which builds excess pressure and might blow out your seals.
 

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could it also be a worn piston seal in the master cylinder itself not causing it to fully release?
If the seal in the master cylinder was worn, I would think the pressure would leak down, and let the brakes release. I don't know the entire trailvoy brake
system, but I would have to agree with roadie. Its not easy to put pressure on and HOLD it on. I would bet on a goofed up ABS valve.
 

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You're guessing. Air would make them soft.

STOP GUESSING. YOU'RE NOT HELPING. A leaky booster would require more pedal effort. What he says is he gets braking action with ZERO pedal effort.
I have helped many of people on here... Just look around.. I don't Guess.. When I first read his post I thought he was saying there are mushy at times and rock hard other times.. I have seen many Vac Leaks in my Time. Just cause I misread a post, does not mean I am guessing.

Please Click the MY RESUME link to show I am no guesser. No one is right all the time.. NOT EVEN A MODERATOR.....
 

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2003 chevy trailblazer_lt
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Discussion Starter · #12 ·
I tried the battary disconnect for an hour and still am expiencing the same problems.

Before all of this I was wondering why I was getting horrible gas mileage, guess this explains it.

If anyone else has any ideas I'm willing to give them a shot before running off to the dealer.
 

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2006 chevy trailblazer_ls
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I'm gonna make an educated guess and speculate that since the battery pull didn't help, and it's very unlikely both caliper seals failed at the same time, that the fault is in the master cylinder, and it's causing there to be just a little residual brake pressure (explains why the back brakes aren't smoking too, cuz of the brake bias).

There's a vent that allows excess brake fluid to flow back in as you release the pedal and the pushrod retracts (see diagram here)

If that vent is blocked, you could have excess pressure. I'd see if something's wrong with that, if it's within your means.

The only components that could be holding brake pressure on are your foot (on the pedal), the ABS module, the caliper seals, and the master cylinder. Anybody (Roadie :)) feel free to correct me if I'm wrong.
 

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Discussion Starter · #14 ·
I'm gonna make an educated guess and speculate that since the battery pull didn't help, and it's very unlikely both caliper seals failed at the same time, that the fault is in the master cylinder, and it's causing there to be just a little residual brake pressure (explains why the back brakes aren't smoking too, cuz of the brake bias).

There's a vent that allows excess brake fluid to flow back in as you release the pedal and the pushrod retracts (see diagram here)

If that vent is blocked, you could have excess pressure. I'd see if something's wrong with that, if it's within your means.

The only components that could be holding brake pressure on are your foot (on the pedal), the ABS module, the caliper seals, and the master cylinder. Anybody (Roadie :)) feel free to correct me if I'm wrong.
is there a way to completely disable the abs unit and rule that out, pull a fuse or something??

is possible to pull off the master cylinder and clean it out?
 

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2002 chevy trailblazer_ls_ext
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just to ad to the list of possibilities.....not likely with both sides grabbing but you also have rubber hoses that could collapse......but one thing I read through this was that they were just flushed, maby sone buildup of some sort was broke free at this time and not flushed out.....if in the right location is could flow freely one way and restrick in the other causing brake drag....it does not take much pressure to cause a dragwith disk brakes...and just a small drag can make a lot of heat making matters worse....

In short my suggestion would be to at least bleed the brakes if not have them flushed again...:m2::confused:
 

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2005 chevy trailblazer_lt
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434 Posts
3 things to look at.

Master cylinder has a leaky seal.
Abs controller needs cycled due to system flushing.
Vacuum system system/brake booster not working properly.

The first and cheapest fix is to re - seafoam the system. You may have
dislodged a chunk and you could clean it out again. It is possible that
the actuator arm from the booster is not retracting enough from the
master cylinder. I would do this first.

Cycling the ABS controller requires an ABS scan tool. This used to be a
necessary step in brake flushing, but not so anymore, unless air gets into the system, which can cause a valve to not release properly.
 
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