How To Fix a Spongy Brake Pedal Chevy Truck

How To Fix a Spongy Brake Pedal Chevy Truck

In truth, this is a video about how to replace and bleed a master cylinder on a C1500, 1990 5.7L to be specific. However, I do have information on how you can solve a spongy brake pedal on one of these trucks by replacing the master cylinder and booster with parts from a later model truck.

Here are those part #’s

Master Cylinder: M390259

Booster: 5471046

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Master Cylinder:


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Silicone Spray:

Zep Brake Cleaner:

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Master Cylinder Bleeding Tool:

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Due to factors beyond the control of EricTheCarGuy, it cannot guarantee against unauthorized modifications of this information, or improper use of this information.  EricTheCarGuy assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. EricTheCarGuy recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video.  Due to factors beyond the control of EricTheCarGuy, no information contained in this video shall create any express or implied warranty or guarantee of any particular result.  Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not EricTheCarGuy®.



Geo M. says:

+ericthecarguy 've done this many times and the best way to me at least is by getting the plastic fitting adapters that fit into the master cyl. ports and then connect a plastic clear hose to both ports and run them into the master cyl reservoir and do exactly what you're doing and you will be able to see when the air is all purged. pump slow so not to aerate the fluid. no mess.

John D says:

Some Pig matts under the part being changed can be used to catch any dripping fluids.

Geo Logic says:

Nice video. What I usually do as a shortcut method is bleed the other end of the short master cylinder lines (where they screw into the proportioning valve). Some people I know would just bleed the master as shown in your video and let the car go, but I just never could bring myself to do that.

The Mighty 460 says:

I'm liking the amsoil cover

Clarence Abrams says:

As a do-it-yourself guy I think you your video is a god-sent

EagleTalons1 says:

I'm not sure about whats going on with your 1990 C1500 but I've been looking into spongy braking problems with my 1997 GMC Sierra C1500 after replacing a rusty brake line that blew on me recently, I did a complete system bleed but seem to have lost my once solid brakes so after doing some research I've noticed people in forums and videos talking about doing a automated bleed (for vehicles with ABS) using certain automotive scan tools to activate the ABS module to burp out any air that may be trapped in the module, evidently even if you do a complete bleed and see no bobbles coming from the bleeders there could still be air trapped in the ABS module.

LazyRutabaga says:

screw it. If you want the best braking, go hydroboost haha

Paul Sosa says:

I have a 2000 F150 I have the same issue I did the same thing. I still have the spongy breaking.

Tiersmoke92555 says:

You getting old boss, but we still love ya.

Patrick Kennedy says:

I have a 90 chevy c1500 that I've driven for the past 18 years and my brakes have always been crap.

AJ Auto Electrical Repair says:

You can make video of newer cars like from 2010 and up

Hector Ortega says:

did you ever goy it working right?. im curious what was tje solution.??

nathan harland says:

I have the same problem of play in my petal after doing mc about 3 years ago and now it is leaking between the hydro booster and master cylinder 🙁

Bill Rimmer says:

The little cylinder below the master cylinder is most likely your problem.

Neil Jack says:

Tried to do this on an '02 Accord. When putting old reservoir onto new master cylinder it would not seat all way down. Well it would go down then it would raise slightly. No combination of pressure or tightening resevoir screw would keep it down. When installed brake fluid sprayed out of seals were it wasnt seated. Anyone ever have this problem?

Kyle P says:


Allen McKinney says:

Hay Eric I just got a used 03 chevy tracker that doesn't have brakes. I was told there was a bad leak but I haven't found any leaks and when I put vacuum on the rear bleeder there's no fluid and the fluid level doesn't go down but when I bleed the front brakes air/fluid came through and the level went down. Is this just bad lines or something else?

Oscar Diaz says:

How about the front calipers?

Matt H says:

I need one of those refillable pressurized sprayers Eric used with brake clean. Please tell me what its called!!!

michael mccartin says:

Great video, Eric! Especially the outtake at the end!! Thanks!

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