Brake pedal Problem (tahoe)

2000 Tahoe…front disc rear drum
Replaced front calipers and pads, rear cylinders, shoes, Master cylinder, brake booster, brake lines rubber flex, Power bled and manual bled… still hardly any pedal… calipers are installed correctly… Master Cyl plugged and tested. ABS has been deleted because 4 repair shops said it was the problem but obviously it wasn’t.
Its narrowed down to the front being soft, rear is hard.
Would it help to gravity bleed for a while the front ? or ? thank you

What does that mean?? Long travel before the brakes apply? Is it soft? Is there power boost or does it take a LOT of pedal pressure to get the brakes on?

Did you do all this work yourself? Who “plugged and tested” the master? Was it bench bled before install? Has it been bled once installed - i.e. crack the master’s lines to release any air?

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If by “hardly any pedal” you mean the brake pedal travels far before it makes any contact, that’s a classic symptom of a problem with the master cylinder, so I’d start with it to check to see if it might be defective or might have been installed incorrectly. Then I’d visually inspect all the newly-installed brake lines, particularly if they’re non-stock and you had to do the bends yourself. Make sure none of the bends are crimped.

If by “hardly any pedal” you mean the brake pedal makes quick contact with the brakes without having to travel as far as you expect it to, that is how I would expect a new system with new pads to behave. It would be a good thing.

And as you have determined that ABS was not the problem, it would be a good idea to “undelete” it. Disabling safety systems is a good way to expose yourself to greatly enhanced liability.

You need a factory level scanner if you want a firm brake pedal.


the master cylinder was replaced by 4 different shops( 4 master cylinders ) all thinking it was bad but wasn’t, and all said the abs was bad and wasn’t… all did factory scan and power bled with no results……. brake pedal will go down about 3/4 or more before its hard but even with that if I keep pressing it will continue down…

With that in mind, I wouldn’t trust their word that ABS wasn’t the issue. If you can’t trust their diagnosis of the problem, I wouldn’t trust their conclusion of what isn’t the problem either.

Don’t fall into the trap of making assumptions that could be errant.

thank you everyone for your input… I appreciate it a lot !!!

What happens if you very quickly and forcefully slam on the pedal? Is it a lot more firm? If so, that’s a good sign that fluid is getting past the MC piston.

hi shadow, the pedal feels the same when softly applied or slam on it

It seems like you’ve done all the right stuff there OP. Good diagnosis job eliminating the master and the rear brake and ABS circuits and power booster. So now I presume the entire ABS system is completely out of all the brake hydraulics, right? And you’ve still got poor pedal even with the rear brakes pinched off? Very frustrating …

(If there was some part of the ABS you couldn’t remove for some reason, that could be what’s causing this btw as mentioned above. It seems like a bad idea to drive the car without its designed ABS system in place. I presume you intend to replace the ABS once you figure out the low pedal.)

hmmm … given everything you’ve already done, and you know the rear is ok, about the only suggestion I can make is to try a couple more manual bleeding methods for the front. My method, and the gravity bleed method.

My method that I adopted many years ago is to just do it myself, without help. Here’s how I’ve always done it, has consistently worked well on my Corolla, Ford truck, and old VW Rabbit.

(Assumes no-ABS issues and the master cylinder is air-free & isn’t an issue)
1.connect clear hose to bleeder & run other end into a catch-container, open bleeder
2.push on brake pedal gently, with one hand (not foot)
3.avoid pushing all the way to the floor, maybe 3/4 of the way max (use block of wood spacer under pedal if necessary)
4.prop pedal down with stick against seat
5.close bleeder
6.release pedal using hand, again very gently, don’t let it spring up by itself
7.repeat until there’s no air pockets in the clear hose, move on to the next wheel, etc.

This seems like it would take forever, but – maybe b/c nobody’s complaining – but it doesn’t seem like it takes long at all. I’d say 1/2 hour max, with coffee breaks. I’ve always had really good results using this method on all three of my vehicles. The key to success is to press on the pedal with your hand only, slowly and gently, and the same when releasing the pedal, slowly and gently. I call it “gravity bleed for somebody in a hurry”. Works for bleeding the Corolla’s hydraulic clutch fluidics too.

Yes the abs is removed… I have not pinched off each line yet but I will, Thanks… I will also follow your bleed steps… good procedure :slight_smile:
Just curios why block the pedal and not push to the floor ?

2 shops tested the front calipers and said there moving great and also holding pressure…
Today I pinched off the front passenger caliper from the rubber hose and the pedal was hard while engine running… I gravity bled it and also did the slow bleeding as suggested… then start the truck and pedal goes down…lol

I’d be looking real hard at the brake line / flex line to that caliper then. It’s rare, but it is possible to have a bad brand new one that lets air back into the system. Also, of course, I’d be making sure all the connections were tight and not passing air. I’d also very carefully inspect the bleeder nipple. Sometimes the nipple’s surface doesn’t match the caliper’s socket and you get a leak.

So you have a hard pedal with the engine running with both front calipers pinched off, but when you remove the pinch and allow brake fluid to flow to both front calipers you get a low pedal with the engine running. Do I understand your findings correctly? I guess the first thing I’d do is see if that applied to both the right and left caliper individually; i.e. is only one of the calipers causing the problem?

I’m guessing it isn’t just one caliper, but both have the same problem. hmmm … are you certain the rotor and pads are both the correct thickness for what the caliper design expects? What if you put a spacer between the piston and the pad (as an experiment only), does that cause the pedal to behave correctly then? If so the problem isn’t air in the caliper, it’s too much distance between between the piston and the rotor.

Note: From what I’m seeing the 2000 Tahoe is configured as either 1/2 ton or 3/4 ton, and the calipers and the caliper pistons and the rotors are different for the two configurations. There’s probably a 2wd vs 4wd difference too, if the 2000 Tahoe could be configured as 4wd.

I limit how far I push the brake pedal b/c by experimentation I found if I pressed the pedal all the way to the floor during my bleeding method some air would get in. I also damaged the seals on the master cylinder one time during bleeding by pushing the pedal all the way to the floor. (The seal damage is more of an issue if it is a used MC, not so much if a new one. )

thank you for your help guys,
With motor running, I pinch off the left front and pedal is hard
I pinch off the right front and pedal is hard…
I bought new rotors and calipers together as a set…
2000 Tahoe Z71 4x4 1/2 ton, old body style ( a lot of parts are from a 99)
-----thought, The parts store said there are 2 MC available for this truck one with 1 1/2" bore size and the other with 2’ bore size… the 2 " is from police edition… I called the dealer and they said my truck is Not police edition according to his computer…
4 MC have been installed all with the 1 1/2" bore…
Is it possible that the 2" MC may provide that extra oomph to fully engage the front calipers ?

adding: when truck is not running the pedal is very hard, only when its running it goes almost to the floor… both front brake hoses are secured and not leaking.

spacers on both sides , so like this with truck running pedal still goes down

No one has asked this question so I will, when the brakes go down, have you tried to pump them up by repeatedly pressing and releasing the brake pedal? If so, what were the results?

truck not running the pedal is hard and it doesn’t change if pumped
Running it doesn’t change when pumped…
Im sorry guys but all this info is true im not messing with you