right front wheel locks up when braking

When driving forward, modest brake pedal pressure locks the right front wheel. If backing up, no problem. 2006 4wd V6, 6 speed, access cab. Has had brake lines replaced, new front calipers, new steel and rubber lines on right front wheel. Was at dealer for brake line replacement. Came home, one start up accompanied by pedal sinking to floor and loud siren noise for 5-10 seconds under hood.

Am stumped on source of problem. Could bad ABS module put all braking on one wheel? Only when going forward?

Suggestions appreciated. If have to replace ABS module, where do you find one?

Thanks.

 

Can you rewrite the specific sequence of events and which steps were done by you vs others?

The way I read what you wrote, it needs to return to the dealer for them to correct their work. But that may not be right, depending on order of the work and who did what.

 

May - dealer does new clutch, says found rusted, leaking brake line and replaced
May - at home next day or so, start up, soft brake pedal goes down halfway, siren noise from under hood for 5-10 seconds, pedal then gets hard
Summer - poor braking
Sept - I pull wheels, rear drums look OK, front calipers frozen, one has bleed screw broken off
Sept - I install new OEM calipers, include new hard line to right front calipers, new rubber line to right front caliper
Sept- bleed by mityvac pull from right rear, left rear, right front, left front
Sept -drives fine
Oct - off on errand, halfway, right front starts to lock on application of brake pedal; if backing up no problem braking

 

Any abs lights on the dash?

 

No ABS lights
Used Maxidas by Autel to scan for codes - none found

 

Can the autel see individual wheel speeds? If it was abs causing the lock ups, id be curious if one sensor is reading incorrectly or dropping out

 

good question, need to check, bu would have thought a bad wheel speed sensor would cause a code and/or ABS light

 

Honestly, I would also think that would cause some kind of fault or throw up a light. But aside from going over everything mechanically. Its the only other thing I could think to check before condoning the abs module

 

Agree, or a mechanical issue with right front caliper, pads; but don't think that since it drove fine for several weeks after new calipers.
If I can find the connectors for the wheel speed sensors and if they are the type that produce a voltage pulse as they rotate I'll put an oscilloscope
on the sensor outputs along the line from the wheels, then figure out what pins/connectors the speed sensors are where they feed ECU. The soft pedal combined with the 5-10 seconds siren noise made me think the ABS pump ran hard that one day, and finding the bleed screw snapped off on left front caliper made me think dealer did not bleed brakes after they replaced rusted line. So maybe air still in ABS module, or some other ABS failure.

 

Could it be the VSC needs to be re-calibrated?

 

What's really confusing is the lock up when forward, but not in reverse.

It almost seems like the caliper or a pad is moving / cocking for some reason.

I think I'd disassemble that and reassemble, lubing movement points and see what happens. Free and easy to try.

 

That's possible (to me). If the trailing side of the pad is bound up, the pad will sit cocked the the leading side closer. When the caliper pushes on the pad, because the leading edge starts closer the the rotor surface, it gets pushed into the rotor sooner. Because it's the leading edge, it acts like a lever or fulcrum to "snag" the rotor. If it was the other way around (leading side bound so trailing side closer), you would usually hear squealing/squeaking but not much a difference as far as stopping

 

So did you get this corrected @Bluetaco2006 ?

Surely you aren't out there driving unsafely?

 

Maybe he's just driving everywhere in reverse?

 

Resolution: Problem found. As one of you pointed toward, right from caliper had lost a bolt, was rotating on the one bolt so it jammed going forward but was OK going backward. Bolt likely installed and not tightened enough by me. Do folks recommend red Locktite on caliper bolts? They were very hard to get off, 17 mm socket on breaker bar with 4' pipe extension on breaker bar handle. So wondered about them being Locktited in versus rusted in.

 

Good job! Feels good to dig in and discover something simple doesn't it!

Blue, because red often requires heat to break the bond.

Have the threads cleaned up and dry (male and female), apply a moderate amount on a few threads, torque, and you should be just fine.

 

Thanks Clearwater Bill! Yes, you are right, all the worry about the ABS module gone, thanks for tip on blue versus red.

 

No loctite is necessary...just tighten the bolt correctly.