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Dan, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1085
Experience:  Dealer Auto Technician
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I have a 07 Silverado 1500 I got at a auction and it has a

Customer Question

I have a 07 Silverado 1500 I got at a auction and it has a very soft brake pedal. I went to bleed the brakes and found the rear brake line at the axle was disconnected .I put it back on and had a friend push on the brakes wile I opened the bleeder. no fluid would come out of the rear lines. I went to the master cylinder (looks new) and cracked the lines, nothing came out of the front brake line (for rear brakes)but shot out of the rear line. I replaced the master and same problem. I hooked up a vacuum bleeder and fluid comes in sperts,no good flow. checked at master again and it shot out good once and went back to nothing. can get a little fluid out if you stomp on the brakes hard. im out of ideas. do u have any?
Submitted: 3 months ago.
Category: Chevy
Customer: replied 3 months ago.
also, have a snap on scanner. it has not codes and I ran it through self bleed several times
Expert:  Dan replied 3 months ago.


There could be debris in abs modulator valve. It may need to be replaced. I have seen these go bad from pushing the caliper pistons back in without cracking the bleeder, it can force debris back into the modulator valve.

If you do replace it flush the lines as much as possible. If the rear brake lines are rubber, they can collapse internally also could cause this problem. The cheapest thing to check would be the lines first.

Please reply to this if you need more help. If you are satisfied with my service, please rate at the top of the screen. Rating does not close out your question. Remember, sometimes it is difficult to completely diagnose your vehicle without being there, but I will try to give you the best answer I can. If I am not giving you 5 star service, please let me know what I missed.



ASE Master Technician

Customer: replied 3 months ago.
I was leaning towards that until I realized fluid is not coming out of the master. What do you think about that?
Expert:  Dan replied 3 months ago.

I miss understood your original question. Did you bench bleed the new master cylinder?

Customer: replied 3 months ago.
That is one of the biggest things that are confusing me. It flowed fine on the bench but not on the truck
Expert:  Dan replied 3 months ago.

Is it the correct part number?

Expert:  Dan replied 3 months ago.

How does the booster look and the push rod?

Customer: replied 3 months ago.
Idk. Part guy said there where two options and I got the same one that was on the truck, but like I said it looked like someone had replaced it already
Expert:  Dan replied 3 months ago.

Maybe they replaced it with the wrong one originally.

Customer: replied 3 months ago.
Expert:  Dan replied 3 months ago.

You could call the dealer with the vin and get the original part number.

Customer: replied 3 months ago.
Ok. I'll get back with you
Expert:  Dan replied 3 months ago.


Customer: replied 3 months ago.
I called and they said they c an not say witch one I am supposed to have. It just says first or second design based on how the Reservoir mounts. Dealer and after market are saying the same thing. I'm going to try the other one to see what happens.
Expert:  Dan replied 3 months ago.

Its the only thing that makes sense. If it flows on the bench and not installed. Maybe the push rod length is slightly different.

Expert:  Dan replied 2 months ago.

Hello again Dan here,

I am contacting you because the post has not been closed or rated.

This question is coming up on 7 days which means it will close.

You have already paid to get this question answered, but you have not rated.

Let me help some more. Is there anything else I can help you with?

If I did not give you 5 star service, please let me know what I missed.

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