Brake pedal goes to floor after I start the engine

[Wiggybaby67]

I installed a new master cylinder and new pads and rotors all they way around. Had to replace the front right caliper as well. After bleeding the brake system, there was a lot of air in that new caliper. The pedal feels good. After I start the engine though, the pedal has no pressure and goes to the floor. Yes, the new caliper is mounted correctly with the bleed screw on top. I was very careful not to draw down the level in the reservoir and I am not getting any more air bubbles when bleeding.
I would appreciate any help
2003 Tahoe LT with 4WD and Automatic transmission.

 

[OR VietVet]

Welcome to the forum.

You can get a pressure bleeder and attempt to do the bleeding. Check you tube videos for the steps. Have seen where the Tech II is used too with the air in ABS system. These brake systems do not bleed out like the older systems.

 

[pa31p]

Maybe a bad master cylinder ? assume it did not do that before you replaced it ?

 

[OR VietVet]

Maybe a bad master cylinder ? assume it did not do that before you replaced it ?

Especially if you bottomed out the brake pedal while bleeding. Should use a 2x4 at the floor to keep from having the brake pedal hit the floor during the bleeding process.

 

[Scottydoggs]

did you bench bleed or bleed the master on the truck? if the masters got some air trapped none of the bleeding works right.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[MassHoe04]

Welcome to the forum.

You can get a pressure bleeder and attempt to do the bleeding. Check you tube videos for the steps. Have seen where the Tech II is used too with the air in ABS system. These brake systems do not bleed out like the older systems.

I did not know this when I replaced calipers... I ended up pushing the pedal to the floor.

I guess I got lucky! I managed to not do any damage. Brakes came back nice and solid.

Now I know to not let that happen... Thanks for the tips, teaching us from your experience!

 

[j91z28d1]

did you bench bleed or bleed the master on the truck? if the masters got some air trapped none of the bleeding works right.

this is what I was wondering too

 

[lisach]

Especially if you bottomed out the brake pedal while bleeding. Should use a 2x4 at the floor to keep from having the brake pedal hit the floor during the bleeding process.

Could you please explain the problem with bottoming out the brake pedal when bleeding? And does this apply only to certain types of brake systems?

 

[OR VietVet]

If you apply it to all brake systems, you don't have to worry about it. In some master cylinders, you can flip a cup inside the cylinder bore if you bottom out the pedal. Can it happen on yours, hell I don't know but if you assume it can and keep from bottoming out, that potential problem is not to be worried about.

 

[rockola1971]

Air is likely trapped in the ABS manifold. You will need a bidirectional scanner to run the automatic brake bleed ABS feature. No way to get the solenoids to actuate without a bidirectional scanner or locking up the brakes and causing the ABS to engage which wont happen since your pedal goes to floor when you start the engine.

 

[Wiggybaby67]

Maybe a bad master cylinder ? assume it did not do that before you replaced it ?

You may be right. It did not do that. I hate when you buy a new part and it still doesn't work right. Seems to be more common the last couple of years.

 

[Wiggybaby67]

Air is likely trapped in the ABS manifold. You will need a bidirectional scanner to run the automatic brake bleed ABS feature. No way to get the solenoids to actuate without a bidirectional scanner or locking up the brakes and causing the ABS to engage which wont happen since your pedal goes to floor when you start the engine.

i got the Innova 5510 which is supposed to support that feature on this vehicle, but it says not supported when I try to use it.

 

[rockola1971]

i got the Innova 5510 which is supposed to support that feature on this vehicle, but it says not supported when I try to use it.

I know the tech II will not connect to the ABS system for the automatic bleed if you have an active ABS code/fault. Try a clear AFTER you connect to the ABS system and run diagnostics on it to record codes.

 

[Larryjb]

I came across this article on removing trapped air from the master cylinder: https://www.brakebleeder.com/removing-trapped-air-angled-master-cylinder/ The angle of the master cylinder may make it difficult or impossible to remove all the trapped air if it is bled in vehicle. Also, even if it is bend bled, could some air enter the master cylinder when installing it?

I don't see this causing the pedal to go to the floor though.

 

[Alex_M]

Air is likely trapped in the ABS manifold. You will need a bidirectional scanner to run the automatic brake bleed ABS feature. No way to get the solenoids to actuate without a bidirectional scanner or locking up the brakes and causing the ABS to engage which wont happen since your pedal goes to floor when you start the engine.

You can jump the ABS relay to bleed thru the module on some vehicles. Have actually never tried on my Tahoe, but certainly worth a shot.

 

[MassHoe04]

I figured I would ask the obvious just to be 100% sure of one thing.

Is the level in the reservoir still up where it should be when the pedal has gone to the floor or did the fluid go down?
Maybe it just needs to be topped off...

 

[Wiggybaby67]

I figured I would ask the obvious just to be 100% sure of one thing.

Is the level in the reservoir still up where it should be when the pedal has gone to the floor or did the fluid go down?
Maybe it just needs to be topped off...

Fluid level is good. Got the power bleeder and will try to use that. otherwise, I will either need to find a bi-directional scanner that supports that vehicle or let a shop do it.