Band

I can find no reference to checking valve adjustment at any mileage. I can't believe that correct clearance lasts forever.
BMW, for one, requires clearance check at the 60K mile service.
Any comments on this?

JoeInHNL

I found the requirement in the "2004 Owner's Manual Supplement: Warranty and Scheduled Maintenance"

In the table of engine maintenance it is listed as Valve Clearance with an "I" for inspect and correct and replace as necessary at 60K miles.

Under "Explanation of scheduled maintenance items" it says:

Valve Clearance
Inspect the tappet noise and engine vibration and adjust if necessary. A qualified technician should perform this operation.

So apparently Lexus Techs are so good they can tell if a valve needs adjustment by sound and feel.

The Haynes manual has checking valve clearance in the tune-up and routine maintenance chapter. It shows the usual method of pulling the valve covers and checking the clearance with a feeler gauge.

I have not heard of anyone actually checking the clearance. The front cylinders would be relatively easy. The back a PITA since you need to remove the upper intake manifold to get the valve cover off.

Band

Thanks, Joe
I saw the bit about "inspecting" valve clearance. I suppose if the valves are clicking, the lash has opened up a bit, which probably won't hurt anything. It will affect valve timing a slight bit. I suspect lash increases ( if any) rather than decreases on these motors.
Since valve lash adjustment doesn't seem to be an issue, I'll cruise on and not worry about it.I've got 83KMiles and a very quiet motor.

thomas1

Yup, had 189k miles on last RX300, and 148k on RX400h and both engines are quiet. Let it go, the new engines are very much better than old yesterday engines.

rcannon409

The ohc motors, like we have, ALWAYS get tighter when the valves move. The clearance goes to zero. Noise is good...no noise is bad. Learned this the hard way on a Honda crf 450 dirt bike.

I said ALWAYS. There may be a case where it wore away and increased, but that wont hurt anything until it gets seriously bad. Its like chains..loose is a thousand times better than too tight.

pauljcl

I thought that any lash was adjusted for hydraulically, as in most modern motors. The oil pressure keeps the clearances tight.

rcannon409

Sorry, I missed this Pauljcl...of course, you are right. However, a lot of modern motors dont use the oil pressure as a way of regulating valve clearance. Motorcycles, and small cars is where you'll see this shim adjustment thing.

Very time consuming to do. First, you have to take a lot of parts off to measure. Then, you have no idea what shim is in place. If its out of adjustment, you need a thinner or thicker one. Awesome, except you dont know what your starting with. You take the cam out, examine the old shim, the order the thicker.thinner one you need.

They use shims like this...http://www.phatperformanceparts.com/photos/29-2600.jpg

Usually, they are just expensive enough that you get angry when you end up ordering three wrong sized ones....which are 100% worthless. Its like trying to buy a pair of shoes when you dont know your shoe size.
Its done this way for light weight. A Yamaha r6 motorcycle makes its power at 15,000 rpm, so the hydraulic pressure would never keep up, but I cant wait for the day when they figure out how to do it!

You then wear up a storm when you needed the next size larger, and repeat this over and over again....

pauljcl

Hi rcannon. Yes, I know well. Some used shims, some used screws. I used to race cars in my youth, in Europe. I remember the shims (patilles of Alfa Romeo well... graduated so finely.
However, the point I was making was that there probably is no need to adjust clearances on the RX350 since it, as most cars nowadays (if not all), have hydraulic pressure clearance adjustment. In essence, it removes the clearance and the need to adjust such clearance when the oil is flowing - thus sometimes the mini 'rattle' upon starting until the oil pressure sets. On the more important point of precision of the valve travel, I don't think it is any worse than it used to be (with the manual adjustments, shims or screws, which were never 'perfect' anyway.

Band

The 3MZ FE engine as used in the RX 330 does NOT have hydraulic lifters to control valve lash. It is a 4 valve/cylinder DOHC motor that uses bucket and shim technology for valve clearance adjustment.
A special tool is required to do the adjustment as well as a micrometer and access to various shims (there are 17 sizes for this motor). Math skills are involved.
There are 24 valves to check/adjust.
This would be a bear of a job were the motor on a bench, but in situ it looks impossible.
I have no idea what a dealer would charge for this service, or when or if it is necessary.
I'm amazed at how difficult this car is to work on, and the outrageous prices charged by the dealer, but that's another story.

pauljcl

I am astonished.... but do you know about the motor for the 2nd gen RX350 which followed the RX330. It had several changes, including changing the belt-driven cams to a chain driven system, like any respectable car should.