Brake problem (almost everything replaced still a soft pedal)

oops…never mind. i’m blaming the dog.

May I step in :)…. 2000 Tahoe(old body style) front disc, rear drums… Replaced rear shoes and cylinders, replaced front calipers and pads,rotors… took it to a shop to have it bled they said master cylinder is bad so they replaced it plus the booster, still no pedal so I took it to the chevy dealer they also replaced the master cylinder and tested everything on the brake system and still no pedal. but said the abs is bad…they gave up and refunded my money and said sorry we don’t know… so i removed the abs unit myself and piped the brakes in directly… had a mechanic bleed system still no pedal… anyone want a free Tahoe ? thank you

If the rear shoes were not adjusted properly, you won’t have pedal. They can be self adjusted by applying and releasing the parking brake repeadly until the parking brake is firm, but sometimes if the starwheel hasn’t been moved first with an adjustment tool, the self adjust won’t work.

thank you, rear cylinders and shoes were replaced and adjusted… I tried your suggestion with the E-Brake… still spongy and pedal almost to the floor… now when truck isn’t running the pedal is hard but when its started it goes south lol

Is anyone who is bleeding the brakes using a pressurized bleeder or are they using the two man procedure? A pressure bleed can make all the difference.

Also are you loosing any brake fluid? Even a tiny amount could be due to a pinhole leak in on of the hard lines that is letting in air.

I agree . . . that’s the professional way to do it, in my opinion

At work, I have my own pressure brake bleeder and all the adapters, so that I can literally bleed brakes on all of the vehicles at my particular location

I can get rid of all the air and force through new fluid . . . without having to pull another mechanic off his job.

Brake fluid is incompressible so has to be going somewhere it shouldn’t when you step on the brake pedal. It’s just a matter of finding out where. Try clamping off the flexible brake lines one at a time, you might be able to narrow down which circuit it is that way. There are specialized clamps you can buy for this purpose, but I don’t know what they are called. I’ve seen them at Harbor Freight. One thing you should check before doing anything else is making sure the calipers haven’t been installed left/right reversed. Believe it or not it is possible to do that, and it isn’t an uncommon reason for this symptom. Check the condition of the flexible brake hoses at the same time, and those going soft can cause this. The caliper bleeder screws must be pointed upward, not downward. You might want to re-post your problem as a new topic btw, if you can’t resolve it quickly.

Found those clamps.

1 Like

Thank you, Its been pressure bled and manual bled several times. Its not losing fluid at all. Bleeders are on top. Hoses seem fine. I will verify the Left/right positions…

You have three rubber brake hoses, I would replace all three and pressure bleed again. Something is giving way, either air or a rubber brake line.

I would readjust the rear brakes again, moving the shoes out until it is difficult to turn the wheel and then incrementally releasing the shoes inward until they lightly scuff the drums.

Hi Keith and thank you, yes there using power bleed and manual bleed both… no leaks and no fluid is lost… I know this doesn’t seem possible but even the chevy dealer gave up on me… The chevy dealer said they even pressurized the entire system and even removed the front calipers to inspect. I have had 4 different shops attempt and they all have had no success. I will suggest to have the “current” mechanic replace the rubber hoses.

There may be one more thing that has been overlooked, especially if you replaced either the booster or master cylinder and that is the clearance between the push rod of the booster and the socket of the master cylinder. If the clearance is too great, you can get the soft pedal. If it is not enough, then the brakes apply themselves but you certainly don’t have that problem.

It requires specialized tools to make this measurement but I have done it with some kids play dough or other clay. Plastigage might work for this as well.

Do you think that the OP meant LOW pedal and not SOFT PEDAL?

Yeah actually because too great a gap causes low pedal when the vacuum is applied, not necessarily a soft pedal. But when you have gone to the end of the run, it can feel soft too.

I think I see your point @keith. Good catch. A really low pedal is very soft when it should be solid.

If I thought there was play between the booster and the MC I’d plug the output lines of the MC and see if the pedal still felt soft/low. If so, then too much space there would be a likely cause. If the brake pedal was firm with the MC outputs plugged, then that couldn’t be the cause.

i did plug the mc on both outputs and pedal was hard…thanks

also one other point……… I had a good pedal before all this started… I only replaced the calipers and rear brake cylinders to make sure I was new before summer ,and then this problem occurred

ok so the front brake hoses were replaced then power bled… there a little better but not rock hard and the pedal still goes down 1 " from floor after pressing. Theres nothing else to replace

Just loved this post…it proves our engineers at the UAW are flunkies…
I assume all the posts below are very accurate. they all achieve some degree of firm pedal on most cars.
So my suggestion is quite different …on the impossible to bleed cars.

by placing a tire lift or car ramp under the drivers rear tire…lift it very high…then start the bleeding process on the lower side right rear.
whats happening is air traps at the very top of the rear cylinders, the bleeder is lower than the air.
so no amount of pneumatic bleeding or regular bleeding will vent this air.
by lifting the opposite side of the car then bleeding the lower side. this clocks the slave in a upward stance
so the bleed port is higher than the air…
do this opposite tire as well…there is no need to do this on the front…if its disk.
Ive never found a disk to be engineered wrong…but slave cylinders YES.

Ive also cured air trapped at master cylinder installs…by lightly tapping the pedal for about 5 minutes after a master install there is no need to do a 4 wheel bleed afterwards.
the check valve returns all the micro air back into the master and its all good to go in about 5 minutes.

motorcycles are specially a bear…you have to tip the bike and use wrenches to tap the lines all the micro air quaglates to one big ball and then it bleeds out.