Foot goes to the floor

MATTCO

MEMBER
1993 ISUZU NPR
4 CYL
2WD
AUTOMATIC

Have a 93 isuzu npr just replaced wheel cylinders on front right and right rear and while there the shoes. This truck has drums on front. After repair bled the system and can't get a solid pedal with the engine running. There is not any leaks. After the bleed the pedal will get solid like it should have sufficient brake application. Although once the engine is started pedal falls and gets spongy just like air in the system. Brake effort on the pedal to stop or hold in reverse takes a strong foot, going forward it will stop though it seems that pedal is too low which does not feel right. What is the proper bleed procedure on these trucks? And could the master cylinder be causing these problems?

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
42,895 POSTS

It sounds like one of two things is happening. Either the brake show are not adjusted correctly or the system has air in it. These are tough to bleed and it must be done correctly or you will have the problem you are describing.

Here is a guide to help you get the problem fixed.

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

and

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Please let us know what happens so it will help others.

Cheers, Ken