Has 140K miles and ran great (always has) when wife took it to the store last night. Went to take the kid to school and loud engine knock at startup and stays there! Sounds like old diesel. Hard to pin down area where it is coming from but sounds like it could be from front cylinder bank. Not sure where to start with this one. Could this be a timing (belt replaced about 7K ago) issue from jumping a tooth or connecting rod or sticky valve? The engine runs smooth in spite of the noise. No fault code. Been keeping synthetic changed since I got it at 80K miles and had no problems up till this morning. Help is needed and appreciated!

 

Welcome to the Club.

You might want to take a look underneath between where the the tranny meets the engine (bell housing) and see if you hear anything there. A busted flywheel can give such a sound like an old diesel.

 

Thanks. Flywheel looks good. VVT components, solenoid valve, cam sensors, and oil screens all check out. Timing belt good, teeth are where they are supposed to be, tensioner good. Going to pull oil pan later and check bearings. Anything I'm missing here?

 

Does you oil light stay on longer tan usual after starting? Does the noise increase with rev? Are you idling lower than usual, any misfiring?

 

Disregard the earlier statement about the timing belt tensioner being good. The hydraulic tensioner sprung a leak and lost most of it's force. It must have caused the VVTi to do something to cause that noise in spite of all the timing marks in place. I pulled the exhaust cams, reset the aux gears, replaced the hydraulic tensioner, and while I was under there (under where) fixed some exhaust problems and serviced the tranny. Fired it up and purrs like a kitten! Just put about 20 miles on it and runs great! As a sidenote: beware of the AC compressor bracket as it hooks under the oil pan and I could not remove it until I pulled the alternator, compressor and loosened the bracket. Said a few things about whomever designed that and something about slamming his hand in the car door!

 

So, had your timing belt jumped some teeth?

 

Heycede- You're not a "hay seed" when it comes to coming back and reporting exactly what happened. It's always discouraging when someone comes to the forums (any forum) with a unique problem, gets help (tips, good or bad) and then never comes back to leave the end solution to help the future "person of need" with the same problem. You did that and I commend you for it! Glad it was no more serious than it was.

 

Thanks Code58, it bugs me too that folks don't follow up but I can understand it. I was pretty stoked when she fired up....quietly! @sktn77a. It did not jump time. All the marks were spot on at first check. In all honesty, I really don't understand how a loose belt could cause that problem. From information from other forums, people with all other models would run into this after changing the timing belt and camshaft seals and it always seemed to point to the VVTi. One thing did happen though, when I took the timing belt off, the R side cam gear rotated about 40 degrees clockwise and made a ratcheting sound. Could have been that VVT gear had advanced from the loose belt and released. If anyone can explain this further, I would be grateful. Thanks to all for your support.

 

HC,
It's quite common for the cams (one or both) to flip forwrd or back because they will allmost inevitably be high centered on a cam lobe on at least one cylinder. All it takes (with the belt off and nothing to stop it) is for it to be SLIGHTLY off dead high center and it follows the natural tendency to flip off that TDC to the side slightly favored. I have read that you should never turn the cam backwards (I believe because of the VVT) but I have had them flip backwards several times and my brother has also, and seemed to have no detrimental effect on the VVT or running, once running again.

 

My wife has a 2002 RX w/ ~145k. In the past 8 months I've had the timing belt, water pump and radiator replaced (in addition to all fluids). Yesterday she pulled in with a loud knocking sound coming from somewhere in the engine, yet no warning lights are lit on the dash. The sound exists at start-up (warm or cold) and quickens with more throttle. It sounds BAD.

Any thoughts? Thanks!

 

I also just had the knock sensors replaced (2 weeks ago).

 

Hi , i have the similar issue on a 1999 rx 300 .... did you find out what it was??? what is needed to fix the knocking noise??? georgedoan@hotmail.com

 

Hello HeyCede
When I purchased my 2007 is250 the engine was quiet with 92k miles. I took it to the dealer for a oil change and the next thing I knew the engine was loud. And it sounds like a diesel. I have taken my car to the dealer 7 times. The first time they told me my water pump was leaking and that is why I hear the noise. I had the water pump changed and still hear the noise. Had the top engine cleaned (carbon build up) and still loud. Contacted Lexus corp and to my surprise the corp manager told me it is okay for the engine to knock as long as the check engine light is not on. I'm tired to being blown off by the dealer and Lexus corp office. I have put less than 2500 miles on this car in the 8 months that I have owe it. Thank God I have a second car (VW bug). After seeing your post, I know I am not going crazy. Unfortunately, I can't take the car apart like you. Can you tell me exactly what I need to change to get rid of this loud knocking noise? Thanks in advance.

 

I was told that the oil pump was going out by an repair shop after he had plugged in his diagnosis computer. STICKER SHOCK for it to be fixed. We drove the car home and the car shut down. Had it towed home. It took me a while to replace bad pump with new one, but finished it tonight. When I went to start it, I got engine knock. Faint when idling, but get louder as I give it throttle. I'm not a mechanic, but if necessary, capable of such repairs. But as for why I have this knocking now, I'm clueless.
Could this have happened when the car shut down before replacement of oil pump or something after new one was installed?

Barrings went out due to oil pump going out?
Knocking will go away eventually?
Did I overlook something?
Please, I need some help with troubleshooting, or definite reason for this.

Thanks

 

Engine knock is generally understood as pre-ignition .. which causes un-even combustion. This should trigger CEL.

Engine noise is another thing and should be referred to as rattling. This can be due to loose component abnormal play. Abnormal play can be due to lack of lubrication. Piston slap comes to mind. I had a cracked heat shield which was causing a rattle,

I would suggest visit a competent mechanic [need not be Lexus mechanic] who is trained to recognize source of the sound and can run some tests to verify.

Salim