garyfisherz0

I’m sure this is something that has been talked about before, but nothing resent so I’m re-opening the subject.
I have a 97 Tahoe that has had spongy brakes ever since a rear hard line rusted through about 4 or 5 years ago, I’ve had this vehicle for close to 11 years and before the line went the pedal was very high and very responsive. If you hit it to hard and didn’t have your seat belt on look out your head is going through the windshield, it was very quick to respond. Now I really have to cram on it to get any response at all. After replacing the rear brake line that popped I blead the breaks several times and probably ran 3 quarts of fluid through it to no avail. Over the last few years I’ve changed the master cylinder, bench bleeding it before installing it. Replaced wheel cylinders also making sure the self-adjusters work and that the shoes are adjusted properly. I’ve changed Calipers, brake hoses, changed all the hard lines to stainless steel. I’ve brought it to the dealer 3 times for bleeding the brakes nothing has made it better or worse.
Right now I’m debating bypassing the abs controller all together and just hooking the hard lines straight to the master cylinder, what do you guys think? I’ve already dumped way more money than I’ve wanted to into this and still have weak brakes, after bringing it to the dealer 3 times and still having weak brakes I don’t have much hope that the dealer is going to be able to do anything for me.
I’m not worried about not having ABS I’ve driven years on vehicles without ABS so I know how to handle a vehicle that doesn’t have it. I also wouldn’t be passing this altered vehicle onto anyone else. I plan on keeping it until it rusts away on me, when it leaves me it’s going to the bone yard.
Would it work to bypass the abs like that? I’ve already had the power wire to the controller unplugged for the last 4 or 5 years, so I know everything else works fine without the abs being powered. I did that because every time I would use the brakes once I got down to about 8mph the abs pump would kick on (even on dry asphalt) and the pedal would drop to the floor and I would lose all break power. It would just roll right through stop signs with the brake to the floor. Weird thing about that is the abs light never came on when it would do that.
Sorry about this being so long but I wanted to provide as much info about my situation as I could.

73shark

Power brake booster possibly?

garyfisherz0

Possibly but if it were the booster I would tend to think that the pedal would be hard to push right?

garyfisherz0

I suppose I should clarify I really have to cram on the brakes meaning there is a ton of pedal travel before I get any response from the brakes. Not that it is physically hard to push.

Suburban Dude

I can’t recommend by passing the ABS unit. A new one at Rock Auto is about $400.

SB

Suburban Dude

I would like to suggest you ask around and try find a shop that could power bleed your system using power bleeder and let them run a few quarts of brake fluid through. I’m thinking you have air strung out through out your system. Make sure the calipers were installed with the bleed screws at the top, not the bottom. If that doesn’t work I think someone sold you a bad master cylinder. It’s happened before!

SD

garyfisherz0

I had it at the dealer 3 times for power bleeding. I even bought my own power bleeder. The one that motive products makes. And still no bueno. I'm assuming like you said that there is air in the system but I think its gotta be in the ABS unit. I have heard that the abs on these needs a scanner to properly bleed them, I have read that they use the scanner to activate the ABS pump while its on the power bleeder expelling the air that gets trapped in the controller. Why the dealer didn't do it I don't know but after 3 trips there I'm done with the dealer. I've looked over the wiring on the ABS system and the motor has its own power wires separate from the rest on the control unit and other wire harnesses. I was thinking of maybe hooking up my power bleeder and using a jumper wire to "hot wire" the ABS pump and see if that works.