I have a 2002 ES300 (135K miles) that developed an uncomfortable squealing noise near the camshaft gear on the forward most head above the alternator. I isolated it down via a stethoscope to the valve cover, tight near where the camshaft comes out of the head to the gear. It almost sounds as if that last bearing is running dry. I searched deep within Google and this forum and didnít find anything significant. I am a second owner and all service has been done on time through the same Lexus dealer. I have all documentation of work done. Timing belt and water pump were replaced at 93K but there was no mention of the idler pulley, tensioner pulley, or tensioner itself. The camshaft seals were replaced and the valve covers were resealed but there was no mention of spark plug replacement or spark plug tube seals. Oil changes between 3-5K with the filter changed at all intervals. The oil looks fine when drained, dark of course but that can be expected. I replaced both serpentine belts hoping that was somehow the cause but no luck. They needed changing anyway. It is much quieter when cold and very noisy after an hour on the highway in warm weather. With it being serviced through Lexus, I canít believe there is sludge build up especially after a visual while resealing the valve covers. There is no mention of anything in the paperwork. I replaced valve cover seals on my 98 ES300 with 120K miles, same service history, and it looked pristine inside.
I have a different timing belt kit complete with both pulleys and tensioner thinking the top idler was going bad but now Iím not so sure. The noise is quieter down lower where the front motor mount attaches to the block. I am good with diagnosis and an above average home mechanic but this one has me asking for knowledge transfer before I start tearing it apart. I know the camshaft mains are not replaceable and I would really hate to replace a head. I am hoping someone has some experience and is willing to chime in.
I would try this first. Take the belt off of the alternator and A/C compressor and listen for the noise. Sometimes alternator bearing noise can travel down the bracket and sound like they are coming from somewhere else. Timing idler pulleys are hard to kill, it takes a long time to wear them out and even at 173k and if it is the original pulley it would probably still be ok. The pulley bearings are nearly the size of wheel bearings and they are not stressed that much so they last a long long time. I take used ones and turn them into casters and have not killed one yet. I have an old one out of an LS400 that I used as a roller under a 7,000lb hangar door and it has been there for a few years without any problem. So I would suspect the alternator bearing first, unless the person who changed the cam seals had scratched a cam bearing or something, cam bearings squeal like hell when they are damaged.
All diagnostic wisdom is earned only from experience and study of other peoples wisdom. That is why I love CL. I get to learn and teach.
The squealing was coming from the top idler bearing with the sound providing harmonics through the aluminum block. I first removed the drive belts for the power steering and the alternator and the noise was still present. With the stethoscope I rechecked many positions around the front of the motor. The noise was still very strong on the valve cover just as before and a spot unchecked before, the head of the bolt just in front of the coolant pressure cap, for the upper motor mount assembly bracket. I previously checked the lower portion of the tall aluminum bracket of the same assembly but it was quiet. Time to check under the covers. I could not remove the crankshaft pulley and needed to purchase a tool which delayed my service for a week. When inside the water pump was quiet, the tensioner and its bearing was quiet, but the upper idler was noisy. When disassembled it had some play. With 40K on the water pump I decided to replace it, the timing belt, tensioner, and both bearings. It runs very quiet now as it should hearing only the ticking of the injectors as the primary noise. I wish Lexus service would have taken the initiative when they did the water pump 40K ago. Now today I need to go in again and replace all the spark plugs since Lexus service didnít do that when they replaced the valve cover seals. Then I should be set for another 100K. Thank you to the two that provided feedback, very helpful.
Lexus won't change idler pulleys or even the water-pump unless you request them too when doing a timing belt service. The standard service is to change the belt alone, and once they're in there and see that the water-pump is leaking and may need to be replaced, inform you.
Regardless, OEM idler bearings are very expensive from the dealer, but these same parts can be had from RockAuto for much less.
__________________ 2005 Lexus ES330
1999 Toyota Solara
I have a 2002 ES300, 281,600 Mi. with exactly the same problem. Exactly! I put the third set of timing parts in a few months ago in February @ 262,000. I ordered my kit from Rock Auto as well. The old idler bearing wasn't bad. In fact, I saved it because I thought I might use it some place. I put in all new parts. belt, tensioner, water pump and idler. The instant I heard this noise today, when I had the hood open after the battery died, Haha, I knew what it was. Like you I kept going back to the cam bearing. It absolutely sounds like that is where the problem is but my stethoscope picked up the noise on the aluminum bracket mounting the front of the engine. I will go through all the "belts off the alternator", etc. but I know it is that bearing. Going in isn't that bad but it wipes out a Saturday, or most of one. Maybe this time it won't take as long because I have a 3/4 inch impact to take off the crank shaft bolt. At any rate, I have a 750 mile trip to take next week and I think I'll take my pickup. I don't want it to fail on the road. I don't know how long this has been going on as you cannot hear it when the hood is down. I guess I'm going to have to get another car one day but I still like this thing. Showing some wear though. I don't think the newer Lexus' are made as well as the 02 and 03 ones were. I will report back in a few weeks.