I was driving down the road and heard a noise (Thought it was a fan or something knocking for about 30 seconds) No lights came on and was running well prior. It quit running and i coasted to the side of the road. When I tried to restart it turned over but a loud knocking noise was coming from the engine. It only has 87k on it. Do you think my timing belt may have broke or any other ideas? I really hope that a lexus with this low of miles isn't having engine troubles. I checked oil and level was fine, no external leaks of any fluids coming out on the ground. All belts and everything visible is fine. Any ideas???

Frank- There are so many things that it could be- so very sorry that it happened to you. Since none of us can unring a bell... all any of us can do is learn from this unfortunate experience. I hope for your sake that it isn't as serious as it sounds. No fluids running out the bottom is good. Accept my sympathies that it happened at all. Please let us know what it was when you find out.
Regards, Roger

Code58 said it so well ... I wrote a few lines but decided not to post.

It can be minor and it can be major problem, Either case you have to get your vehicle towed to a shop you trust.

Salim

engine is shot. oil level ended up being low (weird no indicator light came on) it originally registered on the dipstick when it was hot but when it cooled down there was nothing on the dipstick. Only 87k and I got to bite the bullet. Managed to put 2200 miles on it since the time I bought it. I own a lexus GS400 which has been a great car with 170k on it and only have had to replace balljoints(a few times) I can't believe not even 100k on this RX and major issues. Luckily (if you can say that) can get it rebuilt locally for $1800 plus another $600-700 to pull it out and put it back in. I'm sure they will tell me what the issue was when it's rebuilt. Bad rings or seals to be consuming that amount of oil(come on Lexus lets live up to the reputation LOL)this was supposed to last me 200k no problem!!!! One unlucky guy....

Are you sure your oil consumption isn't due to sludge? It sure sounds like it could be. Others have had the same problem. Pull the front valve cover and take a look. Lexus provided a 8 year 120 day warranty on your engine due to sludge issues. You could get a free engine along with a free loaner from Lexus. Search the forumn for "sludge" or just Google "RX300 sludge" for tons of info and pics.

It was worth a shot!!! Took to dealer and had them pull valve covers, no sludge (unfortunately) The lower end is junk, mechanic hand rotated crank and got stuck, rotated opposite direction and heard something drop down? Sounds like broken rod or other piston problem. Motor had to be previously overheated to be consuming the oil it went through (according to Lexus). I will be pulling the motor myself and mailing out to Oregon where I found a company who will rebuild for $1895 plus $175shipping each way total of $2245 (no tax in Oregon!) engine comes back fully rebuilt with a lifetime/unlimited mile warranty as long as I own it! I found other rebuilt engines and used engines (cheapest $2495) that I can get sooner, but the longest warranty they offered was 3yrs. The total process through Oregon will take 2-3weeks(with shipping and everything) definately not a bad deal when I went to several local shops who came in between $4000-5400 to do the same job. I will try to take pics of the whole process. DIY engine removal and install! If there are any existing links on the subject please post. I am going to start a new thread with that title!!! Also looking for help on the subject(another thread I posted) Es300 short block, is it the same as Rx300 short block?? Found one hell of a deal on brand new block with crank and pistons any input would be great

the upper end may have been cleaned out. The oil pump on a sludged engine pickup screen may have starved the engine. Be very careful about the motor mount locations on the engines you are looking at. They all arent the same, and they are not drilled out on the block to accept the different locations...Do your homework up front. These folks otherwise will put you through bad times if you have to return the engine. They dont want to pay freight for a return. Yes I speak from experience with my neighbors highlander. We finally gave up on the rebuilds and rebuilt the original engine.

Where was this engine rebuilt in Oregon?

Not sure if you noticed but that was almost 4 years ago....

Wow ... that was helpful. I imagine that any number of shops have been open longer than 4 years and remain open today.