My 2000 RX300 has 145,000 miles. 10 years ago I started hearing valve ticking. I found both #2 exhaust valves had too much gap. The other cylinders 4 and 6, were OK. I ordered thicker shims, nearly the max thickness and replaced them. The ticking is coming back. I checked the gap now. Facing the engine, the left exhaust valve had over 0.025 clearance. The right exhaust valve was OK. Compression is around 120 pounds. Not great, but should not effect the valve clicking. The cam lobes look good. I can think of only two options, the valve still is wearing, which means pulling the head, yuck. The other option is the valve bucket wearing, probably where the valve stem makes contact, The bucket could be replaced by removing the cam. Not easy, but easier than pulling the head. I don't want to throw a bunch of money at a 25 year old car.

A third option would be to make a shim to go under the main valve shim as a spacer.

Has anyone run into this before?

 

Possible cause is the bucket itself is wearing which will cause a slow progression of too much clearance. The shim is extremely hard material it easily lasts the life of the engine, the bucket itself is relatively soft. There are scattered reports of the bucket itself wearing causing your issue. On the compression test what were the other cylinders or did you test them?

 

Back in the early 00's, we used to stock the buckets and sold them quite regularly... now I haven't sold one in years...

 

Thank you for the quick reply. This is my first Forum posting.

I may order some buckets from Lexus On Line. The Lexus dealer here jacks up the prices. I needed to replace the thermostat on this car last week. The dealer wanted $125 for the thermostat and O Ring. Lexus On Line wanted $5 for the O ring. The dealer charged me $21. I thought it was special. NOT. Plain Jane.

The compression for cylinder #2 was 120 pounds, cylinder #4 120 pounds, and cylinder #6 was 150 pounds. I did not have the throttle open. I forgot.

If the bucket is soft steel, I may have a steel spacer made to fit under shim. I can have one laser cut so that it would be flat.

 

Don't do this, if the bucket is worn and damaged it will continue to wear until it completely fails destroying the cylinder head in the process. Sources for a replacement bucket
https://parts.belllexusnorthscottsda...751-74020.html
https://www.amayama.com/en/part/toyota/1375174020
https://www.ebay.com/itm/317202968271

 

Wondering if this is the same cause of my tapping noise @SSDi

did your RX sound like this or different?