Fluid and friction sounds when braking- any ideas?

Vehicle: 2018 Toyota Highlander SE

Issue: Grinding/Friction Rub and Fluid noise when braking

Details: On Feb 23, I replaced all 4 brake pads and front rotors. Ten days later, I noticed an intermittent grinding/friction sound when braking. Three days after that I started noticing a fluid sound occurring at the same time as the grinding. It’s now two months after doing the pads/rotors and it’s still doing it.

Things I can say I’ve been able to confirm:

  1. Temperature is a factor. On the colder days, it would take 20-30min before I started to hear this. On a few 90 degree days, it happened within 10min.
  2. Only happens at low speeds (under 15mph). Definitely more noticeable going down hill.
  3. The fluid sound comes in at the few last second or two before coming to a complete stop. I do not hear the fluid any other time (not during turns, acceleration or any other braking)
  4. The noises cannot be heard from outside the vehicle. The grinding/friction noise can be felt and heard within the car, and a front passenger can also feel it.
    I’ve checked my ABS sensors to make sure they were clean and clear. I’ve topped off coolant (which was near full anyway). I’ve check the pads and rotors - doesn’t appear anything is wrong there.

Help, please. I’m about to lose my mind!

Sounds like your ABS is coming on when it should not. Try a slow speed stomp on the brakes ABS stop and see if it feels and sounds similar.

Also drive the car for 15 minutes or so then pull over and check the temperature of each wheel… the metal part. If one is warmer than the rest, you have a sticking caliper and that be causing the ABS to activate when it shouldn’t.

I had this problem on a GM truck… solved it by adjusting the torsion bars to eliminate a sag. One front wheel wasn’t loaded as heavily as the other and the ABS read that as a skid. Sounds strange but it was the issue. I doubt it is your problem simply because you did not touch that part of the car.

I’ve heard grinding sounds from brake parts before, but I don’t believe I’ve ever heard fluid sounds … hmmm … beyond the good ideas about an ABS problem above, maybe the fluid sound isn’t coming from any brake parts. It could be there’s some rainwater that has pooled somewhere, and you hear it sloshing around when you apply the brakes. Two guesses, water in the door, or water in the catch pan under the A/C evaporator. Given the temperature relationship, seems more likely it would be the A/C catch pan. When you run the A/C or defrost, some water in the air will condense on the evaporator surface & run into that pan. It should drain out under the car onto the ground, but maybe the drain is plugged. Not an uncommon thing.

Another idea for the sloshing sound, could indicate a problem with the fuel tank. Seems unlikely, but should still be considered. Take notice if the sound changes immediately after a fuel refill.

For the grinding sound that started 10 days post pad/rotor replacement, that shouldn’t happen. Suggest to take car back to shop and ask them to inspect the brakes. Maybe they miss-installed something during the original job.

I was hell bent on it being the ABS. I disconnected the ABS module and figured I’d drive it a bit to see if I could recreate the symptoms. Unfortunately, I don’t think I did this long enough to definitively say yes or no. My car was freaking out with so many bells and chimes, and I was too nervous to drive too far/too fast without a functioning ABS.

I’ve checked wheel temps several times but doesn’t seem any of them differ in temp. I could’ve sworn the first day I heard the grinding that I caught a whiff of smoking brake pads when I got out of my car, but it went as fast as it came and I couldn’t find it again. It may very well be a stuck caliper. I’ll troubleshoot this, too.

Thank you!

Why? We drive cars for 100+ years without ABS and survived. I am will to bet you’ve never experienced a serious 4 wheel ABS event on dry pavement.

I, too, thought I had a drain plugged somewhere. But I literally don’t hear it until I do a slow brake. Never turning or accelerating. And it would seem the pan is draining fine as I’m seeing usual amount of water under my car after running the AC.

To be more specific, the fluid sound isn’t really a sloshing. It’s more like bubbles. Almost like a kid blowing bubbles in their milk with a straw.

Thank you!

Haha - you’d lose as I used to be a dumb kid.

But, I get your point. I suppose the majority of the concern is my lack of knowledge about just how integrated the ABS and the sensors are into other safety functions in the car.

I could always try again. It wasn’t a complicated task.

Any thoughts on it bring brake fluid in the vacuum side of the brake servo?

Is your brake fluid mysteriously disappearing with no apparent leaks? If so, yes, that is a possibility.

bubbling sounds from the brake system? this is indeed quite a mystery! About the only thing I can think of that would sound even remotely like that would be the ABS self-test, which I’ve never heard b/c neither of my cars has ABS, but is often reported as a sort of buzzing sound that occurs for no apparent reason. Buzzling, bubbling, could sound somewhat similar I guess.

In the way of misery loves company, Ray and Tom on a recent podcast had a caller who was hearing a “whishing” sound whenever she moved the gearshift from P to D, 1, or 2. Ray identified this as a vacuum leak. That caller’s car had a weird feature, it automatically released the parking brake via a vacuum actuator whenever the gearshift lever moved out of P. The vacuum actuator was leaking.