Grinding noise from front end during fast U-turn

Did any dash warning lights come on? ABS or TCS, both systems sense wheel speed, and in a sharp uturn, there is a difference in inner vs outer wheel speed that could have been interpreted as wheel slippage.

 

might your rotors have been rusty from non use and hard braking bypassed regen?

 

Mine does the same, but isn't replicable on a consistent basis; like when the service tech drives it. I also have a clanking noise whenever I hit a bump or bot dot that's most likely from the brake shoes slapping around as it goes away under heavy braking, which also isn't audible to the service tech. I don't see any evidence of tires rubbing causing the u-turn noise so I suspect it has something to do with the abs being applied. I'm going try to find a quiet road with a gravel turn out and drop the front wheel onto it and hit the brakes. If it makes the same noise, then it's the abs.

 

Put your Prius in neutral (shuts off regen) going about 25 MPH and apply the friction brakes lightly. If it makes the noise, just repeat until you clean off the corrosion on the rotor faces.

JeffD

 

So I tried the abs test. It works. Car comes to a stop fast! But the noise wasn't exactly as the one I get when u-turning. Also, when u-turning, I'm not on the brakes, I'm accelerating. The noise happens towards the end of a u-turn and when it does, the front dips and the car slows slightly so maybe its traction control slowing one of the wheels? I haven't noticed the yellow traction light lighting up though like it does when abs comes on.

 

I would honestly say that whatever is occurring, is normal. If it wasn't normal - you would have probably been notified by some warning/notification lights. If you're really that worried take it to a dealer and have a mechanic sit in with you while you reproduce the issue.

 

It's possible that there's a splash shield that's gotten bent in such a way that it's close to the brake rotor.

In quick, tight turns the knuckle, hub and rotor deflect a little and that might be enough to bring the splash shield (or a brake pad clip) in contact with the rotor.

 

I have the exact same problem. It happened to me twice already, randomly might I add. I can't replicate it for the life of me. Please update is if you find out what the problem is.

 

I have had the same exact issue as well. 2011 Prius II w/67k mi. It's been happening since December 2014...almost 6 months at this point. I first heard it when making a u-turn. When the front end is under load, I notice it almost every time. It will also make the creaking-crunching sound when backing out of the driveway on a slight slope, coming to a stop downhill, coming down canyon's curved roads, also when braking while going over speed bumps when the front of the car is under load.

I worked at a Toyota dealership and they couldn't find the problem. They all heard it. Service Mgr. thought it was suspension. 2 techs thought it was suspension. A 3rd tech thought it was connected to my brakes somehow. I threw money at it trying to fix it. Replaced the whole front suspension. Still making the noise. Just glad I had a discount! I also had the front rotors resurfaced. Still making the noise. Dealerships won't fix anything they can't hear. In my case, they heard it but couldn't find it. Since I was an employee...I felt they didn't get to the problem b/c I wasn't a regular customer. Gonna go back to get it looked at again at 70k when I'm due for oil change. I have an extended warranty as why I'm going back to Toyota. I feel once the vehicle is warmed up, the car will start making weird noises all over. This particular noise is really getting to me. I purchased the vehicle new and never missed a service. Always taking care of any issue and extra maintenance items done on time.

I am beginning to believe it is connected to the braking system somehow. The brake actuator/assembly motor as well. When the brake is pressed while driving over speed humps, it makes the crunching noise (like a bad strut). When going over same speed hump, without pressing the brake, it doesn't make this sound. I will post update after my 70k service.

 

yours is the first one doing it consistently. the problem is trying to replicate it while someone is looking underneath. difficult to put the suspension under tension, like when 3,000 pounds are trying to move forward with the brakes holding them back.

 

Wouldn't holding the car in place with brakes while headed down a sufficiently steep hill simulate that condition?

 

Same thing happened to me today for the first time. I was making a u turn and about halfway or toward the end of the uturn there was a startling noise like abs or something grinding and the orange light on the dashboard (abs?) came on for a second. 12,000 mi on the car. Just had maintenance done last week.
I may try to do some more test u turns in a parking lot or the 25-mph neutral braking suggested above.
I was not going that fast on the u turn, maybe 10-15 mph. I was turning to the left.

 

Exactly. One of the techs at Toyota mentioned to put it up on alignment rack and put some weight on it to see if we could get it do make the noise while he was underneath but we didn't get to it before I stopped working there. Pushing on the front suspension doesn't duplicate this condition either. Also, I've noticed while at a red light fully stopped, foot on brake pedal, the ICE will shut off and I will hear another crunching sound from the wheel area. Once it is warmed up and always at a stop sign or red light, the ICE shuts off, the sound will appear when it is turning off. I've tried with the same conditions, this time vehicle in Neutral, the ICE shuts off, no sound at all coming from the front wheels. Not sure if it is connected but it might be. It started at the same time. I'm gonna hit up a different dealer this time to check it out.

 

engine mount?

 

I have the same problem and I believe it's either brakes or "charging system" related. I got my prius brand new (with 600 miles on it) at the dealer and the grinding sound randomly started when braking not long after. At 2000 miles I went to the garage as the VLC light turned on twice and I thought I lost brakes for a moment, going at 20 m/hr on a dry asphalt, I tough all those were related. I kinda had an idea how to trigger it so I was able to make them hear the sound and when it happens. No error code was generated, they took my brakes apart and they filed a claim at Toyota head office to check for similar problems. Nothing came back from Toyota and they didn't find anything wrong with the car.

I am now at 7000 miles and it's been worst since they gave it back to me. I know exactly how to trigger it now so I try to avoid doing it but here are my observations:

-Happens every time I smash the brakes in emergency situation regardless of the speed (pressing the brakes lightly won't trigger it)
-It sounds exactly like the sound it makes after you turn off the car and wait for about a min (I assume when the charging system kicks in?)

I read a lot of post about similar problem but nobody figured this one out.. I found info about the VLC light lighting up and the brake lost problem so I'm good with it but this noise is extremely annoying..

 

Sounds very similar to my problem. Yes it is extremely annoying. I never had any warning lights come on though. I don't want to get rid of the car but there are multiple other sounds I'm experiencing. Are you planning on taking it back in to get it looked at?

 

I have thought about this. I just wonder why none of the guys at Toyota pointed to it as the potential issue. But like I said before, they aren't so keen on wasting time diagnosing when you're an employee. I will look into the engine mounts. Thanks for the reply!

 

Not yet.. I was thinking bringing it up at my next maintenance. I'll keep you posted.

They light was a different issue (apparently normal after reading some info in here). The grinding sound while breaking is on it's own.. When they check I feel like they only check the "light turning on problem" and totally disregarded the sound problem. They checked the brakes and kept the car overnight waiting to hear back from Toyota head office. For safety reason they didn't want me to drive to car until they were sure everything was ok.