Bled brakes for first time. Not sure it went so well

2005 trailblazer - 80k miles. Recently bought and have been going through changing all the fluids as only the oil has ever been changed. Did the transfer case and both diffs which went fine. then it was time for the brakes. I read that gravity bleeding was the safest and easiest so I went with that being my first time. I hook a clear hose to the bleeders and ran into a bottle. I cracked them and let them trickle out. I was refilling and the MC NEVER went even close to empty. I ran each one until fluid was clearish. I made a big mess when the hose kept pulling off the bleeders but otherwise seemed to go fine.

Until I went to drive it and found I could push the pedal to the floor. I took this to mean I had introduced air into the system. But searching online came up inconclusive as to whether it’s normal (on some cars) to be able to push the pedal to the floor if you try. It doesn’t need to go anywhere near the floor to stop. In fact, it’s very responsive and firm up top. I only have to press a little bit to stop the car. And if I hold it there, the pedal stays without dropping. But if I put anymore pressure to it, it’ll go to the floor without much effort. Doesn’t sink at traffic lights. When engine is off, it takes 2-3 short pumps and then gets rock hard. turning on ignition makes it drop a little and it does have pressure but if I push, it’ll go to the floor. the biggest issue I think is that I can’t pump up the brakes when ignition is on (not that I’ve needed to). I pump and pump and I can feel it gain a little hardness and then that goes away and it’ll sink from the pressure I was putting on it when it was hard. this is the only time it “sinks”. Before bleeding brakes, the pedal was inconsistent. At times it felt ok and at other times it felt kind of mushy. I mostly didn’t like the inconsistency and the fact it was 15 year old brake fluid. I don’t know if I could push the pedal to the floor but never noticed that I could.

I just replaced all 4 pads a few hundred miles ago. Rotors looked ok. No vibration, no noise, no pulling and I used a IR gun to check temp on all 4 rotors for a few days after the change and they all were the same as before the pad change (and both sides matched each other for front and rear).

So I thought maybe I managed to screw up the easiest and safest bleed method and bought a vacuum pump set. What a POS. It holds vacuum but I can’t get it to pull anything but air and a few drops of fluid when cracked. None of the included fittings work and I tried zip tying but that only helped a little.

My other thought is the master cylinder but shouldn’t it be sinking instead of holding pressure a stop lights?


Thank you. That certainly does sound like it could be the issue. Unfortunately, I just went out and looked around and couldn’t find any bleeders on the module. Just 2 rubber covers that have ports underneath. The module had Delphi 2 marked on it.

Looks like I may have to take it to the dealer then as I don’t have access to a scan tool like this.

  • The hose from the brake valve should run into a catch bottle half- filled with brake fluid, so the end of the hose is not exposed to air. Positioning the catch bottle higher, up to near the top of the tire can be helpful to avoid air getting in.
  • Experiment with several bleed hose attachments to find one that fits the bleeder valve as tight as possible
  • Best to bleed tone wheel at a time. RR , LR. RF, LF appears to be the sequence for a 2005 Chevy Blazer 4.3L V6
  • It may be necessary to pressure bleed the system after the manual bleed procedure is completed, to get all the air out.
  • Likewise may be necessary to run the ABS automated procedure

Don’t drive the vehicle until the pedal is firm. Bleeding the brakes should return it to the same firmness, or more firm. If it is less firm something is wrong.

Thanks. the gravity procedure instructions I saw said it didn’t need to be in a bottle of fluid if the pedal wasn’t going to be pushed (like this: Was that incorrect? I did do the correct wheel order.

the pedal actually is firm and stops the vehicle without pressing it much. But if I push it more after I’ve already stopped, I can get it to the floor.

Unless it did that before the bleed – in which case you have a unusual brake system design – that means there’s something wrong.

If you bled in the correct order, and did only one wheel at a time, with the remaining valves tightly closed, I’m guessing the problem is the other end of the tube wasn’t under a layer of brake fluid. Or air got in at the tube/bleeder interface b/c the tube was larger than the bleeder valve and letting air in. If that’s the case it is good news, b/c the air is most likely still in the calipers. Re-bleeding while addressing the above might well return you a firm pedal.

One idea is to try it again, but this time press on the brake pedal to expel the brake fluid faster. Put a 1-2 inch thick block of wood under the pedal, so that the pedal travel is limited. Press on the pedal with your hand, not your foot, and gently and slowly You’ll need a helper to open the close the bleeder valves in coordination with your brake pedal pushing.

I’m honestly not sure if it did it before (I’ve not had it very long).

I did all that except for the tube under fluid part. I’m curious why so many of the gravity videos and articles don’t have the other end of the tube under brake fluid. In fact, some specifically said to start with it empty so the fluid could be measured. I’m also wondering if I did put it under fluid, what about the air in the tube?

I’ll see about getting someone to assist me. Good idea about the block of wood. I hadnt seen that mentioned in the various stuff I’ve watched & read. I’ll see about getting my wife to help me this weekend.

You can prove the problem is in the calipers by clamping off all four flexible brake hoses. If you then have a firm pedal you know at least one of the calipers is the only problem. On the other hand if you still don’t have a firm pedal you’ve got air in the system problems upstream. Clamping kits are available from auto parts stores , Harbor Freight, etc. The idea is to spread the clamping force over a larger area to avoid damaging the hose.

There was somebody here in the past 3-4 months who was having this same problem. They were trying all the tricks, forget what the problem eventually was. You might be able to find their thread using the forum search feature.

I don’t know if this will help but I encountered this problem on older cars when either the the reservoir to piston hole was clogged or the reservoir was allowed to drain dry. Air was allowed into the piston so the pedal would go to the floor.

The first step is to check the that the reservoir to to piston hole is clear then allow the piston to refill (give it time to leak down or slightly more aggressive means). Then completely redoing the flush, reservoir cap open, using the “2 person, hose in the bottle method” while carefully watching to see that air doesn’t get in from either the reservoir or calipers…

If that doesn’t cure the problem or the “mushy” comes back, carefully check for fluid leaks, around the fittings, rubber hoses and piston/caliper seals while your helper is pushing on the brake while the vehicle’s parked and the system’s under pressure.

Depending on your ability, because stopping isn’t a luxury, this may be the time to visit a good mechanic.

Do an automated brake bleed with a pro-level scan tool

This is under “functional tests”

A cheapo code reader won’t do this, because they aren’t bi-directional

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The reservoir never went dry while I was bleeding and since the fluid was never changed before, I’m guessing its never gone dry. I do think someone was topping it off as the pads wore and then when the pads were done, they didn’t pull any out as the level was nearly to the top of the reservoir. I pulled it out down to max and then when I did brakes, it went right up exactly where I originally found it. So I brought it back down to max line.

Would you happen to have any links on the piston refill? I am interested in doing that but don’t quite know what you’re describing doing.

I’ve looked everywhere for fluid leaks after driving and haven’t found any and level is always the same. But I will look around when I am doing the 2 man (I mean 1 man, 1 woman : ) bleed.

I contacted a local dealer but haven’t heard back. Gonna try a couple things and if no improvement, will take it somewhere.

Sorry, I don’t have a link but at it’s most basic, think of your brakes as simple pumps in a sealed system and the brake pedal as the handle.
When you push down on the handle/pedal, it forces down a piston in the master cylinder, which pushes a noncompressable fluid to pistons at the wheels (wheel cylinders) forcing them open and pushing your brake pads against the rotors. When you release the brake pedal, springs at the wheels reverse the process, fluid coming back to the master cylinder pushes that piston and your brake pedal back up.

Everything’s fine and dandy until you have a leak in the sealed system, letting out noncompressable brake fluid and letting in compressable air, giving you that “mushy” feel so it’s now “find the leak”.

**First, most important and hopefully obvious, “chock it” and don’t move the vehicle AT ALL without proper brakes!!! **

A ton of metal moving at even 5 mph can do serious damage and injury so don’t even think about moving it!

Starting with the easiest first, inspect all the external components. My own experience has been that it’s easy to accidentally let in air while doing a “gravity bleed” so check that and then the rubber hoses, fittings, etc. for leaks while the system is under pressure.

If no leaks there and the vehicle isn’t pulling to one side while braking, it’s time to move on to your master cylinder, which is under your brake fluid reservoir, a metal pump with 2 tubes coming out.

Assuming no leaks, as you press on the brake pedal to bleed your brakes, that pump should be drawing fluid from the reservoir, which you would have needed to periodically refill during the bleed.

If you let the reservoir run dry during the bleed, you may have let air into the master cylinder and redoing the bleed may cure it.

On the other hand, if the fluid level isn’t dropping or your problem persists, your master cylinder is probably “going bad” (technical term :wink:). and the solution is to “take it to your mechanic”.

And again, brakes are not a luxury, they’re a SAFETY ITEM and if you have any doubts at all, take it to a professional!!! And tow it if it’s at all questionable!!

Thanks taking the time to write all that. I do understand most of it but want to make sure I have everything covered when I go to try something.

the part I wasn’t sure about was this one:

“The first step is to check the that the reservoir to to piston hole is clear then allow the piston to refill (give it time to leak down or slightly more aggressive means)”

Do you mean to check the area externally? And then give some time after pressing the pedal for it to refill before bleeding? Or are you describing something I need to do manually?

The thing is, I have test driven it each time after I try something else and honestly have no doubts about its stopping abilities. I’ve checked every type of stop I could and it was great on all of them. the pedal doesn’t travel to the floor during stopping ever. When going down an off ramp at about 40 (with no one around), I jammed on the brakes to see how far the pedal would go down and it was firm and didn’t move any further than halfway before I couldn’t push down anymore. its when parked (engine on) or going at a very slow speed that i am physically able to push the pedal all the way. though the vehicle stops long before this happens, so it only ever goes down all the way when the car is stopped and only because I decided to keep pressing it out of experiment to see how far it’ll go. I’m not convinced something is even wrong, but I’m not convinced there isn’t so I keep researching. I find a good number of posts around the net from trailblazer owners complaining of mushy pedals and some have replaced MC, booster, bled and bled and bled, bled ABS and still feel it’s mushy. I wish I could test drive someone else’s similar trailblazer and see how the brakes are but I don’t know anyone.

I also took it on a gravel road and tested ABS a few times. They performed just as they did before all my brake work had been done.

If my bleed this weekend doesn’t change it, I’ll have a pro evaluate it. I’m half expecting them to tell me they don’t feel any issues with it.

Just found this thread about someone describing the same thing when they bought a new trailblazer in '05.

I’ll start looking around the trailvoy forum that someone suggested in another thread.

EDIT: Have only spent a few minutes there and already seeing this is very common on these vehicles, if not normal. Numerous people describing exactly what I’m feeling. I’m still going to bleed again just to make sure. I may also replace the MC anyway since its something I can do myself and not too expensive.

Ok, I just went out to take a test drive and the pedal is quite improved. I didn’t notice this improvement right after doing the ABS stops last night but definitely today. this is also what happened with a number of people on the trailvoy forum. Doing a few ABS stops helped lessen the pedal’s travel and keep it firmer as you push down. If I try to push my pedal to the floor now, it gets quite firm and starts to creak like I’m going to break something if I keep pushing so I don’t.

Now I have a couple more questions. Should I still bleed it again? I’ve read a number of people who bled, had spongy brakes and then did ABS stops to firm up. But no mention was ever made about bleeding them again. they just seemed satisfied that it was all good now. Is there not old fluid in the ABS which has now been released out into the brake lines? Or is that not how it works?

Oh, also I went out to do a test on the booster I read about online which needed the valve pulled off. I’d never actually done that so I wanted to see how it comes off. I came out by just pulling evenly and firmly. And then there was a big rush of air. It held that pressure for over 12 hours so I feel good about the booster and didnt bother further testing.

Here is THE answer to that question . . . I already answered it yesterday, as I recall

Pay a shop to perform the “automated brake bleed” with a pro-level scanner

And then you will at least know that everything has been done correctly, and you can sleep well

And so can the rest of us that share the road . Brake work is not trial and error exercise.

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not to complicate things, but this seems worth consideration:

how much did you crack / loosen the bleeders?
if they were loosened too much, air can go in thru the threads while fluid comes out the bleeder

I found the most effective way to bleed brakes is the 2 person method. I may gravity bleed or vacuum bleed, but I always use the 2 person method when I’m done. Something else that I’ve noticed that when I first started bleeding brakes on cars more than just occasionally, it seemed to me that the pedal went down further than what I was used to from when I did it years ago. It seems that with antilock brakes they are a little more spongey towards the bottom than old conventional brakes. That being said, some vehicles almost always need special bleeding procedures for anti lock brakes. Not all antilock brake systems need scanners to bleed, but most may need scanners on occasion. My recommendation is to do the best you can with a 2 person bleed, pay attention to how the brake pedal reacts, just like you have done. Then bring it to a brake specialist, and have them check it out. Tell them what you have done and that you want them to check your work especially the bleeding. When you get it back, you can see how the brake pedal feels compared to when you brought it in. If it’s the same, and you get a good job well done attaboy from the brake specialist, you know you can do a good job and you know how the pedal is supposed to feel. The expense is worth it because you may have learned how to do brakes. That’s cheaper than a college course. Also as mentioned afore everyone is safer.

Interesting. Do you have a theory why the gravity bleeding method isn’t able to do the job itself? It seems like the gravity method has to work as long as

  • air has no way to enter the system above the bleeder valve as it drains
  • each wheel circuit has plenty of time to complete the bleed

The only way I’m can envision air entering a system that worked before is perhaps when re-filling the MC as required some air bubbles get into the brake fluid then. If that’s the source, then the solution is to wait awhile after re-filling the MC before continuing the bleed.