Major “break problems”

Guys my 06 keeps loosing the pedal, changed booster, master cylinder, calipers.... no one can figure out why. Pedal was fine for about a week then right to the floor, sometimes even pumping it doesn’t work. Has anyone else seen this issue? No fluid loss at any wheel or master cylinder. Bowl is full

Could a faulty abs module being causing this?

It happened with my girls in the truck Wednesday and by Gods grace we didn’t crash

it’s an 06 4x4 trd double cab, 4.7L

 

Check the wheel bearings for play, and the rear shoe adjustment. But if it was fine for a week, and pumping sometimes doesn’t help, it makes me think the new master cylinder has failed.

 

Wheel bearings?

I Thought the same about the master but because it’s the second one so I don’t believe that’s the issue.

even if the rears were out of adjustment a lot, could that cause it?

thx

 

When this happens, is the master cylinder still full of brake fluid?

 

Yes every time

 

My truck is not modified in any way

 

For the most part, the MC from the t100 is an upgrade for ours. I don't think anyone has tried anything else. Would be nice though....

 

Does it make any weird noises when it does it? Like fluid being pushed around?

A faulty abs would make it kick the abs on below 5mph, or not at all.

This wouldn't be caused by loosing vacuum to the booster, would it? I think that would make it harder to push...

 

The only thing not replaced is the ABS module, but not sure if that can be faulty and cause a soft pedal

 

I'm 100% sure it can't. Mine was/is faulty and actually caused the pedal to kick back all the way and no braking at all.

 

The fact that it's only soft sometimes is what I don't get. If you had air trapped somewhere it would be soft all the time. You bench bled the master cylinder both times?

 

abs doesn’t kick on at all when it goes to the floor, and there are no noises at all, unfortunately not even the abs kicking in. And I agree bad booster would be rock hard pedal

 

Not trying to de-rail this thread, but I have a 15/16" bore MC to compensate for rear discs, had a 13/16" bore stock. Think the T100 mc is 1" bore.

This should be very easy to check, pull out the vacuum check valve from the brake booster and blow in it both ways per the FSM.

 

No sorry it’s every time you break once it starts happening about a week after replacing master cylinder

 

Did you bench bleed the master cylinder? Maybe you do have air somewhere. I'm an expert on screwing up our brakes-trust me.

 

On this truck bench bleeding isn’t done on master

 

I just made an appointment with a shop that only deals with Toyota and Lexus because I took my girls to camp this morning and almost took out a cop at a stop sign. Scared the shit out of him and my girls when I had to dirt track the corner

 

Sounds good. Let us know how it goes.

 

We had a member who I haven't seen in a year who used... dare I say the F word... a Ford MC successfully. I can't recall what truck it was out of, when I read it I immediately dismissed it. He has a build thread somewhere, big black first gen with an American flag on the roof. @Rheywood456 I think

 

PROBLEM SOLVED

Guys I can’t thank you all enough for the quick responses trying to decipher this issue. So I went to the garage yesterday and the problem seems to have been fixed.

when the master cylinder was done and the breaks were blead, the garage never adjusted the rear breaks before bleeding. They were way out of adjustment and when you pumped the breaks you could hear the back breaks clacking. The mechanic said they were really busy the day they were done and that they didn’t have time to adjust the rears at that time, so I would have to come back another time to adjust the rears. And they did seem to work fine for about a week before the pedal started getting soft again. So I asked even if the rears are out of adjustment I have two bran new calipers on the front, shouldn’t they be kicking in? He said the pistons on the drum breaks are large enough to hold enough fluid that when you push the breaks enough fluid goes into those that makes the pedal soft and that causes an issue of not enough pressure in the lines getting to the calipers to activate properly.

absolutely crazy! The garage not finishing the job properly could have killed my kids and me. Lesson learned, ALWAYS make sure the drum breaks are adjusted properly before bleeding the whole system.

thx again guys hopefully this thread can help someone if they ever come across this issue.

 

Sounds a bit like a sketchy shop. Time to find somewhere else to go. Besides drum brake systems don't have pistons, only wheel cylinders. Drums on these trucks are supposed to be self adjusting as well. Although I think I've heard others here say that sometimes that doesn't work too well. Glad all is well now.

 

Seems to be the norm. Either don’t know what they’re doing or they can’t be bothered to take the time to do it right the first time.

 

I agree. If they weren't making contact with the drums, it would've been mushy, but would still work, even a week later. Did they fix it for you?

I know this from experience. When I did my rear bearings I put all new rear brakes on and adjusted them all the way in. My parking brake is severely out of whack so they aren't self adjusting. My brakes worked, I just had a mushy pedal for a while as the fronts were doing all the work. I've since adjusted them and re-bled the system, as well as pulled my ABS fuse(for an unrelated issue). Pedal travel is long, but the brakes work fine.

 

that’s the puzzling question I had, why was it fine for a week? Don’t have answers for that, they did continually get softer and softer, but to me that part is puzzling.

 

there is a piston on drum breaks that press the pads out and they hold quite a bit of fluid so that part made sense to me.