I just bought a preowend RX330 and when I break not all the times but sometimes i hear like a knoking noise under the car. Not sure if it's coming from either side of the tires, but does anyone know what this might be? It's not loud or anyhting but I can fell and hear it when I press down on the breaks. I read on another posting that this might be the calipers or pads that need to be adjusted, but I have no idea...if anyone out their can help me figure this out I'd appreciate it. I hate to take to the the dealer and being a female be talked into major repairs when I dont need them.

Thank you,
Brenda

QB- Do you have anyone who can take a look at it for you? A male friend or relative? It does sound to me like either the caliper bolts are loose or the pad is moving in the caliper because it's not a good fit (loose) or if it has "tensioners" to hold it tight (quite a few cars do), that they have been left out. (I don't believe they can just come out) I would try and find someone knowledgeable who would at least do you the favor of taking a look at it for you. If you are going to drive a Lexus, I strongly advise you to start looking now for a GOOD HONEST COMPETENT Lexus or Toyota independent shop (before you need it) Anyone who works on and specializes in Toyota should also be able to work on your Lexus- they share so many similarities in drivetrain and design thinking. Probably be cheaper too!

Thnk u letting me know this iam actually going to ask my husband to chck this out. We just weren't sure if it could be something else. I will get back and let you k ow how it went.

Well I had my husband check this out n he said everythng with my breaks looks fine. Dies any
one what else it may be?

My 1999 rx-300 started doing something that sounds like this a couple of months ago. I saw nothing wrong with the brakes. I thought it might be an ABS problem so I pulled the ABS relay (its in the fuse box in the engine compartment) and the problem stopped. I guess there is a problem with the ABS, but I dont know what yet.

Brenda, Have your RX checked for abs/vehicle speed sensor dtc's.

Queen B- I think maxSteel and eatingupblacktop have steered you in the right direction. I didn't even think about the ABS. It may be dirt or rust or damage to an ABS ring on one of the axles (1st place I'd look) or it may be something actually wrong with the ABS unit. I would check and clean the ABS ring and sensor at each wheel, but be careful because if you have to replace any of those parts it's quite expensive. Good Luck!

So is this somethng my husband can check or will I have to take to a dealer so they can check it out. If were talkng somethng that has to be replaced do you happen to know what Ian looking at to pay? I should of just got the extended warranty now having huge regreats.

There are a number of threads on abs repair, including how to read the brake codes. It can be expensive.
Before worrying about it try the relay and see if the problem stops.

Brenda- I would take maxsteel's advice and pull the relay to see if the problem goes away. If it does, I would next see if you can find "how to" thread on cleaning the sensor ring (1 at each wheel, looks like a gear) and the sensors for the ABS. That may cure it, but as I said be careful in cleaning them.

Ok so I took it back to the dealership I bought my rx from. The results of their findings is that the noise is my motor mounts that when I break it's causing it to shift. They are going to repair it this Friday. Do you guys think they have found the issue?....

From your original description I doubt that is the cause of the knocking, but I have been wrong before. I have had broken mounts and have known many others who have had broken mounts and have had a lot of other symptoms that would indicate broken mounts, but have never heard of any that would be described as "knocking" that could be heard and felt when you apply the brakes. Will be interesting to see if the mounts cure the problem.