JAB

I am the original owner of this 1999 AWD RX300, delivered in May 1998. I had a timing belt service at 95K in January 2004. At 215K I had it done again last week (April 2014).

There has been considerable discussion of what timing belt service interval did Lexus recommend and what other parts should also be replaced. A review of the Maintenance Supplement to the Owner's Manual describes certain 'special operating conditions' which require additional maintenance; if the vehicle is primarily operated under extensive idling or low speed driving for long distances the timing belt should be replaced every 90K; however, if those conditions apply only occasionally (this describes my situation) THERE IS NO RECOMMENDED REPLACEMENT INTERVAL!

Regarding other parts frequently replaced at the same time as a timing belt, on my recent service in addition to the timing belt I had the tensioner, both idlers, cam and crank seals, thermostat, water pump and accessory drive belts replaced. Out of curiosity I dug up the service invoice for what was done at 95K and much to my surprise the ONLY things replaced (by my independent mechanic) were the timing and accessory drive belts. So, except for the belts everything else had 215K on them. An inspection of the idlers revealed no signs of bearing failure and the water pump was similarly silent and had not leaked. I can't speak to the hydraulic tensioner. The accessory drive belts were obviously worn but in no danger of imminent failure. The only parts that were visually in need of replacement were the cam seals - oil leakage was obvious. My timing belt was indistinguishable from the new one.

I am curious whether Lexus changed its recommendation with later year First Generation RX300.

kalali

Thanks for sharing your experience but you left out one important detail and that was the condition of the actual timing belt. How did it look after 125K miles?

hypervish

I wouldn't gamble it because the engine is an interference design.

However, I do believe the timing belt can easily go beyond 90k miles. My Sienna has 144k miles on its original timing belt, I'm risking it since that 1MZ-FE does not have VVT-I making it non-interference.

If I recall correctly, there was a thread on CL about an LS that went 220k miles on the original timing belt.

JAB

Kalali: Thanks; a sloppy edit of the original text caused that observation to get deleted; I have corrected it.

Hypervish: I am aware of the risks associated with timing belt failure in an interference engine. Which makes it all the more suprising that Lexus took a risky approach to the issue.

sktn77a

iTrader: (2)

Well, the issue here isn't the average lifetime of a timing belt (MTBF) but rather the 0.001% on the early end of this life expectancy. So most people could happily go 300,000 miles or even 500,000 miles on the original belt but one or two of them will have a failure at 60,000 miles, 10 - 20 at 90,000 miles, 100 - 200 at 150,000 miles, and so-on. Same applies to any component in the car. Example, my RX300 is still on its original water pump at 170,000 miles whereas my LS460 is seeping at 60,000 miles and will need replaced soon.

fastnoypi

I am on the skeptical side of things, perhaps from the older mechanic's rule of thumb that you should replace your waterpump and idlers while doing your timing belt. It is the whole hassle and labor to get in the area to do the job in the first place and it is piece of mind to refresh with all new parts. I would certainly replace the hydraulic adjuster with a new one vs having the mechanic repress in a vice/c-clamp. Though you may be able to reuse the adjuster, you have to have 100% trust that the seal was not blown by clamping the pin too fast.