Brake "groan" when slowing after a bumpy section?

Hey all. I tried to search this, but I don't really even know what to enter to search. I have this wierd sound that happens when braking after a bumpy section while going relatively slow (like 10-20 mph) mostly off road, and I'd really like to know what it is. It's like a mechanical groaning sound that seems to be coming from the engine compartment. It's hard to describe, so forgive me... It sounds almost like a mini air compressor that runs for 1-2 seconds. I get no ABS light or anything, and no noticable difference in feel. Anybody have any knowledge of this or hear something similar?

 

I get three noises offroading. Brakes up front groan. Drums groan pretty bad. Then there is TRAC kicking in... which does not set off the skid control warning.

 

I'm 99.3% sure it's not coming from the brakes themselves--definitely coming more from the center of the vehicle in the front. What is the TRAC?

 

on my prerunner, if im braking and i got over a random bump a lil hard it groans up front and the brakes loosen up...toyota says nothings wrong but its happened with my friends in the car and they've heard the noise n have see me pump the brakes around twice to come to a stop...

 

Sounds similar, but I've never felt the brakes loosen--just hear the groan. I wonder if it's an ABS component that just makes that noise?? Did toyota explain what it was, or just say it's nothing wrong? (so helpful they are sometimes...)

 

Lol i get this all the time. it usually happens if im comming to a stop sign where theres a puddle and i brake too hard, so the ABS kicks in.

And ive heard it happen when i was braking to a stop and my front passenger side tire hits a patch of mud.

My guess its just normal ABS operations.

 

"we have inspected ur vehicle and everything is perfectly normal"...thats what i got 3 times i went in before 36,000...so...no help what so ever...damn dealership...sorry bud.
i got nothin

 

Gotta love the stealership.... Thanks for the info!

 

no problem...n thats after i rear ended some chick who thought i was crazy that i couldnt brake...no damage tho. but my friends believe me after it happeing to them

 

Sounds like normal abs operation to me. Slam on the brakes in loose dirt. Without abs, your wheels lock and you slide. Since you have abs, that system will kick in. Whatever noises you are hearing as you come to a controlled stop are normal.

 

My guess its just normal ABS operations.



Yeah, mine does it also (makes noise and brakes are very soft) going over large bumps in the road - scary when the brakes don't work!!

I imagine the noise is the ABS system under the hood as it "pumps" the brakes for you.

I think the ABS engages itself because it thinks some wheels are skidding, as it goes over the bumps.

 

ya i figured it was the abs (after a lil while later) so i dont really pay much attention to that unless it happens

 

My guess is this is whats activating. because to me it always sounds like its coming fron the passenger side under the hood. Sorry for the crappy quality, i took this with my iphone

 

You all rock--I feel a lot better knowing that this isn't just my truck and that you all think it's the ABS. That was my suspicion too. I'm going to have to pay attention to the brake pedal next time to see if it seems to go soft (huh huh) when that happens.

Thanks again all!!!

 

No Problem