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More about timing belts

I just found out my 2001 Lexus LS430 has a timing belt that needs to be changed. It is a non-interference engine, so I planned to change it when it broke (no cost unless the belt breaks). However my local Lexus mechanic says if the belt breaks at high speed (70 mph? 80 …?)there could be catastrophic damage. Is he right - should I change the belt now, or can I safely wait until the belt breaks (if it ever does)?

However my local Lexus mechanic says if the belt breaks at high
speed (70 mph? 80 …?)there could be catastrophic damage.
Is he right

Assuming he’s right about it being a non-interference engine, then the only “catastrophic damage” you’ll need to worry about is to you and your passengers.

Do you really want the belt to break (and instantly lose all power) when you’re on the interstate between a few tractor trailer trucks? Or when you’re accelerating to avoid a merging car?

Have it changed. No good can come from breaking down, only bad.

In addition to Joe’s excellent scenerios, it could also break down in a bad neighborhood or in the wee hours of the morning in a pouring rain, driving snow, or even bad hail storm.

pay a little now, or pay a lot later, your call.
You obviously don’t want to keep the car, so let it break, the freak out when you get the bill for fixing what’ll need fixing when it breaks, then compare it to what it would have cost to replace it before it broke.
I’ll suggest starting to look for cars that have timing chains on them, so you know what to look for when something happens.

This is the scenario I have seen, an engine labled “non-interference” damaged by a high rpm belt breakage. Has anyone ever had the heads off one of these engines (I have not) are the pistons flat,a bit of a dome, are there valve reliefs cut into the pistion tops? I wonder how Lexus gets good HP without some heavly lift on the cam and a good shape on the top of the piston

I simply could not believe that a 300hp 4 cam V-8 with variable valve technology was a non-interference engine, I looked and it is called “interference engine” NOW are there two possibile engines that could be used, I doubt it.

Let it ride, if you feel you can handle the car if the motor suddenly stops - including if you are traveling at 70+ mph in the passing lane of an interstate highway. If you can live with that, the motor repair won’t be that much as a non-interference engine will simply need a new belt and all the timing marks lined up again. Not a big deal.

Since it is a 2001 it is really up to your comfort level with a sudden failure. If I was driving, not a big deal. If my wife or kids drove this car primarily, then that’s a different story.

Never fails to amaze me how someone can sink the bucks into a luxury car then they’re too cheap and careless to take care of it.

This is probably the second most valuable thing you own and you want to treat it like a toaster?

Reminds me of a guy I saw when I was buying tires at Costco. He had a Lexus, the big one, and he was looking for the cheapest tires he could find. He did not want to pay for the tires that the car was rated for because he didn’t drive over 112 mph or what ever it called for at the time.

Your car does have an interference engine. Change it yesterday.

My favorite location for such break down; train tracks.

One of my young co-workers installed the timing belt incorrectly on a LS430 and 5 valves broke when he tried to start the engine. The service department paid for new valves and pistons.

Your vehicle DOES have an interference engine. Timing belt failure will not only leave you broken down at a location determined by the decision of your timing belt, but will cause a lot of very expensive damage to your engine. Even if it did not have an interference engine, while the repair bill would be no higher, what if your car broke down 150 miles from your repair shop? Or on your way to work or to catch an important flight? Or on your way to the emergency room with a critically ill or injured spouse or child? You shouldn’t try to plan for a breakdown or assume it will happen at a convenient time for you. Prevent the ones you can rather than pressing your luck.

Here’s the site you go to to determine if your vehicle has an interference engine: Input your car’s information, and if you see red letters that say “interference application”, you have an interference engine.

My info says this is an interference engine.

Manufactures do not use an interference design simply to make people angry. The interference design is a path to high performance, mind you I am not saying the only path. I recently read of where GM has been able to achieve variable valve timing with the use of a single cam located in the traditional, center of the “V” in a V-8. Lexus manages to get reliability(there is an aircraft variant of this engine) out of this 4 cam V-8 32 valve engine in spite of using a belt (where BMW uses a system of chains). I have never timed (as in setting up the cams) the Lexus but the BMW is a job you want to be shown the highlights of before you are let loose on your own.

According to Gates website the 2001 430 is an interference engine. Change it or not, its your car and your money.

I don’t see any harm in his reasoning, why should anyone pay extra for high speed rated tires if they never intend to break 100?

There’s also the issue of heat dissipation, lower the speed rating the less likely a tire is to be able to lose the heat build up through friction, a heavier car like the big lexus will tend to make more heat in the tires, the engineers who designed the car know this. And then there’s the issue of traction, a tire with a lesser speed rating may not provide the level of traction that the engineers had in mind.