Need help with no brake pedal

[SUBURBAN5]

The front calipers and mc are ac delco not sure on the brake booster or the rear drums.

Most likely there good. Dont sweat it. But I've just had new part be defective before

 

[Schurkey]

I started by replacing the brake booster, master cylinder, rubber lines and the front calipers... ...I ended up running nearly 4 gallons of fluid through it between traditional bleeding, scanner on the abs, and pressure bleeding.

Describe your procedure for bench-bleeding the new master cylinder.

I got it back and tried some isolation tests with plugs. I have hard pedal at the master cylinder. I couldn’t totally isolate the abs since the front right is a different fitting of course. With just the front right I have brake pedal like it was originally, kinda squishy but still had a bottom. As soon as I add either the other front or the rear brake lines the pedal disappears. My current theory is that the valve body isn’t functioning properly but any insights would be greatly appreciated!

Use a pair of vice-grips (needle-nose preferred) to LIGHTLY clamp the two front rubber brake hoses, to verify the rear brakes. Then LIGHTLY clamp the rear hose to verify the front brakes.

When I say LIGHTLY, I mean that the hose has to be clamped shut, but without excessive stress on the rubber. Don't clamp the hose more tightly than it takes to collapse and block the fluid passage.

If you had the steel-braid-over-Teflon (PTFE) brake hoses, you wouldn't be able to do this. Clamping those hoses ruins them.

the shop I took it too had the exact same suspicion but they replaced the whole assembly and it only improved slightly.

Did they properly adjust the rear brakes?

I’ve been borrowing a friends and his is a really fancy snap on one. I believe it’s a solus plus.

Is it set-up to read brake codes? It's not going to display brake codes if it's set up to read engine codes.

 

[evilunclegrimace]

Few things. 1 abs module matters. Specially for 1/2 to 1/2. 3/4 to 3/4 and so on. Model matters. Suburban has more weight then a c 1500 short cab as an example. May not be your issue but keep that in the back of your mind. As for your scanner it's good enough IMO. You want to communicate with the abs module and see if there's any brake codes. For example no communication or faulty solenoids. Normally the scanner will display what ever. Kind of like trans codes without a "fault light on" . Last I would definitely follow the fluid like you were doing. From mc to abs inlet to outlet to rr wheel cylinder and so on. Are your parts OEM or some cheap aftermarket? Duralast, brake best, ac delco?

K1500 pickup -K1500 Suburban take the same ABS Module. GMPartsGiant lists the module as PN 12474923 for both trucks.

 

[Schurkey]

Ehhh. It's been radio silence for the last month-plus.

 

[evilunclegrimace]

Ehhh. It's been radio silence for the last month-plus.

Yeah, i don't always read the date of the last post.