Temporary loss of brakes

[east302]

Truck is a 1998 two door Tahoe.

I took a hard left through an intersection trying to make the light. I sped up to get to it and had to hit the brakes fairly hard while making the turn. The road is sloped such that it got kind of tippy—not quite Dukes of Hazzard but close enough that I’d just stop for the light next time.

About a mile down the road, traffic screeched to a halt from 50-ish mph. The brakes damn near went to the floor. It felt like having drums only or a leaking master cylinder. The brake pressure light did not come on and brake pedal feel returned to normal once I started again.

It’s fine now.

The master cylinder is full and the pad/rotor thickness looked fine a few weeks ago when I replaced the shocks.

Any idea what happened?


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[Justin S]

Not that its the same exact thing, but my old 2001 silverado had the same problem, did it to me 3 times over the course of a month. I would go to slow down and as i pressed the pedal it would drop to the floor, then the next pump it would be back to normal. It ended up being one of the rear calipers. The calipers were bad, and i think the piston would back off and stick and not be fully pressed against the pad, and every once and a while it would randomly free up, causing the issue. I ended up swapping to rear drums and it never happened again. Maybe that happened to one of your fronts?

 

[east302]

Do you remember it pulling to one side?


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[Justin S]

Do you remember it pulling to one side?


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Since it was the rear, no, but if yours pulled then check out the side opposite of the way it pulled in the front

 

[east302]

I don’t think it pulled at the time, but think that it may have in the past under moderate braking. Every now and then, I have noticed what feels like very slight ABS pulsing at the last bit of brake pedal travel on moderate to hard stops.

But, it’s without the normal noise and commotion that you hear and feel when the ABS system activates. It doesn’t feel like rotor runout, either, and it’s only felt in the pedal.

It’s not consistent (I can’t duplicate it) which kind of sounds like your caliper issue.



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[big_mike]

Listen closely when you press the brake pedal, if you hear an "whoosh" like sound when the pedal goes to the floor without much resistance, if so it's the brake booster on the firewall. Simple fix.

 

[Schurkey]

Use the brakes HARD, then the next push--soon after the HARD stop, the pedal goes to the floor?

First HARD stop may have boiled the water-contaminated brake fluid, second stop needed excess piston stroke to push enough fluid back to the calipers/wheel cylinders to make up for the fluid displaced into the reservoir when the fluid boiled.







NOT common after one stop. Used to be very common on long, downhill (mountain road) grades.

 

[Supercharged111]

How crusty are your brake lines? If you brake like a real man who loves America and tries to turn aggresively in a direction other than left, there does exist the remote possibility of pad knockback caused by a worn wheel bearing. This requires some real gusto though.

 

[east302]

Thanks for the replies.

I’m not hearing the vacuum whoosh sound, the brake pressure is back to normal. But I still feel a grumble in the pedal if I push it to the floor.

The fluid is dirty, not sure when the previous owner flushed it so that is on the list. The brake lines are original from what I can tell. We don’t have snow or salt, so there isn’t the rust issue.

Beats me, guys. It would be easier if it did it consistently. I’ll probably get into it this weekend, see if the ABS sensors are nasty and regrease the caliper pins.


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[tinfoil_hat]

I had this happen to me out of the blue on the freeway one time. I was cruising along about 75mph with plenty of room up ahead of me when the whole lane came to a stop. I had plenty of time but when I hit the pedal nothing happened. I was standing on that pedal with two feet and my butt out of the seat. Stopped a foot fom the little import in front of me.

When I got home I looked around the wheels and driver's front was smokin hot. Looks like that one caliper was dragging. Not an issue with my normal 40mph five minute drive to work but the speed on the freeway probably made it so hot it faded to nothing.
I pulled the caliper and the bolts had a baked on build up of grease. Cleaned the bolts and boots, relubed, and the brakes have worked fine ever since.