This is not a how-to, but I will share a link to an excellent how-to. Just want to share my experience.

I bought a 2002 GS300 November of 2022. It had 176,000 miles on it and it ran very well. I didn't get any comprehensive maintenance records with it so I purchased a CarFax report that showed the timing belt had been replaced at 90,000 miles, and I believe they are to be replaced every 90,000 miles. With now 180,000 miles on it, time for a new belt. Additionally, it seemed to be dripping oil, not so much that you needed to add oil between 5,000 mile changes, but enough to notice on the garage floor.

I had twice changed timing belts on my Miata, so I felt if I took my time and was deliberate this was doable. After watching an hour and 21 minute, pretty much step by step how-to on YouTube ( ) I decided to do it myself.

An Aisen timing belt, water pump, timing belt tensioner and idler pulley kit from Rock Auto along with sparkplugs, OEM valve cover gaskets, thermostat, 2 camshaft seals, front crankshaft seal were purchased to begin the job.

A wobble extension set is just about mandatory for some of those hard to get at locations and a crank pulley holder is highly recommended and made getting the crank pulley bolt off and on a breeze.

Followed the how-to video and all went smooth until the connectors (3) used to attach wiring to the coils crumbled as the video suggested they might. I found another video ( ) that shows how to overcome this problem in the minimum of steps.

As the job proceeded it became clear that part of my oil dripping problems was leakage from the intake cam gear which contains the VVT-I mechanism that is controlled by oil. There is an o-ring within that cam gear assembly that as it gets old and brittle allows the leakage of oil. Lexus does not sell the o-ring and recommends you by a new intake cam gear. - $263. Meantime you can find the o-ring elsewhere for less than $10. There are a few YouTube how to's, some that show you how with the cam gear off the camshaft and some on the camshaft. I did it on the camshaft. Watching the videos you'll see that stretching the o-ring and mounting it before it returns to its unstretched position is the tricky part.

Watching the videos you'll see that a lot of care and attention is given to keeping the crankshaft, the camshafts and the cam gears properly timed. You can ruin the engine if you loose the proper relationship and I found that the videos were sometimes redundant. For me, the main thing was turning the engine slowly over by hand to make sure there was no interference and all the marks continued to line up as they should.

The car ran very well before I did this work, but I think maybe the new plugs improved my mileage by 1 mpg, and the oil dripping disappeared. One thing I noticed was you couldn't tell the difference between the new belt and the old one with 90,000 miles on it.

 

hehe, that’s what everyone says.

nice job, but I almost never ever hear an issue with people stretching the timeline with their original OEM belt.

 

GS 400 owner here.

I also just replaced my timing belt, for the same reason as you, I’m also at 180k miles and I also had little drops of oil on the garage floor.

My belt also looked just like the new one, so that 90k interval for the timing belt might be a BIT conservative lol.